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Polyhydroxyalkanoates (PHAs) are thermoplastic biopolyester with high biodegradability and biocompatibility. This review explores the potential of PHAs as promising alternatives to conventional petrochemical plastics, offering a solution to reduce plastic pollution. The strategic selection of conditions, including type of microorganism, carbon substrates and extraction methods, enables the effective PHAs production for maximum yield and cost-effectiveness. Recent advancements in characterization techniques, each with its own advantages and limitations, are explored to offer insights into PHA concentration, composition, and purity. This review highlights the versatility of PHAs in various applications, focusing on medicine, environmental remediation, industrial processes, and agriculture, where they can offer significant environmental benefits by replacing non-biodegradable materials. Despite production cost challenges, PHAs demonstrate promise for sustainable polymer development. This review contributes to advancing PHAs as a viable solution for eco-friendly applications across diverse industries. • Diverse cultivation and extraction strategies were explored to optimize PHAs production. • Characterization methods for PHAs include microscopy, spectroscopy, and chromatography. • PHAs are versatile and sustainable alternatives used in medicine, environmental remeidation, industry and agriculture. [ABSTRACT FROM AUTHOR]

Medium-chain-length polyhydroxyalkanoates (mcl-PHA) are biobased materials with promising properties for environmentally friendly applications. Due to high production costs, which are related to the cost of the carbon sources combined with conversion insufficiencies, currently only small quantities are produced. This results in a lack of reliable data on properties and application potential for the variety of polymers from different types of production strains. This study investigated the potential for the production of mcl-PHA from volatile fatty acids (VFA) at a larger scale, given their potential as low-cost and sustainable raw material within a carboxylate-platform based biorefinery. Pseudomonas citronellolis (DSMZ 50332) was chosen as the production strain, and acetic acid was selected as the main carbon and energy source. Nitrogen was limited to trigger polymer production, and a fed-batch process using a pH-stat feeding regime with concentrated acid was established. We report successful production, extraction, and characterization of mcl PHA, obtaining a total of 1.76 kg from two 500-litre scale fermentations. The produced polymer was identified as a copolymer of 3-hydroxydecanoate (60.7%), 3-hydroxyoctanoate (37.3%), and 3-hydroxyhexanoate (2.0%) with a weight average molecular weight (M w) of 536 kDa. NMR analysis indicates the presence of unsaturated side chains, which may offer additional possibilities for modification. The results confirm that there is a potential to produce significant amounts of mcl-PHA with interesting rubber-like properties from waste-derived VFA. • Successful pilot scale production and extraction of significant quantity of mcl-PHA. • Pseudomonas citronellolis can produce a small fraction of unsaturated monomers from acetic acid. • Oxygen limitation is present only during the exponential growth phase. • Pure acid can be successfully used in a pH-stat setup. [ABSTRACT FROM AUTHOR]

[Display omitted] • Management of organic fraction of MSW (OFMSW) and excess sludge is difficult. • Anaerobic codigestion of these two substrates in presence of bioplastic is analyzed. • Influence of bioplastics on methane production has not been evidenced. • Bioplastic biodegradation is very limited and the presence of fragments is evident. • A possible increase in phytotoxicity has been also signalized. Co-digestion of the organic fraction of municipal solid waste (OFMSW) and excess sludge has several benefits especially related to improved methane production and better process stability. In recent years, the presence of biodegradable plastics is increasingly common in OFMSW especially since, as in Italy, biodegradable bags are used for its collection. In this paper, the influence and the fate of biodegradable bags during anaerobic co-digestion of excess sludge and OFMSW are assessed. The best results in terms of methane yield (about 180 NmL/g VS) have been obtained with the 50:50 (VS basis) co-digestion of excess sludge and OFMSW with an organic loading rate of 2 kg VS /m3·d. Bioplastic degradation is very limited during the co-digestion but it does not influence methane production or digestate chemical characteristics. However, the feeding of bioplastic bags seems to induce a higher phytotoxicity and the presence of undigested fragments is anyway a problem for further treatment or direct utilization of digestate. [ABSTRACT FROM AUTHOR]

Bacillus cereus is a gram-positive bacterium belonging to the Bacillus genus. It is widespread in several ecological niches and has interesting genetic and metabolic properties that allow the production of polyhydroxyalkanoates (PHAs) with suitable physicochemical properties for several biomedical applications. Despite the numerous publications over the last 20 years dedicated to reporting the isolation of this bacterial strain and its PHA productive capacity, more information on several important points (such as biosecurity controls, the use of agro-industrial by-products as substrates for PHAs production, genomic mining strategies, fermentative studies at pilot scale, the propose of novel PHA-recovery protocols based on techno-economic and ecological studies, and certifications of the biopolymer obtained) is still needed before B. cereus could be proposed as a model for the industrial production of these biopolymers. Hence, this review discusses the properties of B. cereus as a potential PHA-producing model and highlights the areas of opportunity for future research on this bacterium. [Display omitted] • B. cereus is a promising alternative for polyhydroxyalkanoates (PHAs) production. • Interesting genetic and metabolic properties. • Ability to produce heteropolymers from a sole carbon source. • PHAs with suitable properties for biomedical applications. [ABSTRACT FROM AUTHOR]

Rising concerns around plastic pollution from single-use plastic (SUPs), especially food packaging, have driven interest in sustainable alternatives. As such, algae biomass has gained attention for bioplastic production due to algae's rapid growth and abundant polysaccharides. This research focuses on extracting carrageenan from Kappaphycus alvarezii , extensively cultivated in Sabah, Malaysia, and utilizing it in combination with starch and glycerol to develop algae-based films. The physicochemical properties and degradation rate of these films were evaluated, revealing that the addition of carrageenan enhanced overall thermal stability meanwhile increasing water solubility, water content but reducing the degradation rate and swelling degree. This is primarily due to the crystalline structures of carrageenan, which provide a more rigid arrangement compared to the network of starch polymers. However, the incorporation of starch into the blends has enhanced the elongation and surface morphology, resulting in more balanced properties. Overall, these carrageenan films displayed impressive thermal, mechanical, and biodegradability characteristics, establishing their viability as substitutes for conventional plastics. [Display omitted] [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO 2) is a common pigment used in food packaging to provide a transparent appearance to plastic packaging materials. In the present study, poly(butylene adipate- co -terephthalate) (PBAT) incorporated with lignin-TiO 2 nanoparticles (L-TiO 2) eco-friendly composite films was prepared by employing an inexpensive melting and hot-pressing technique. The P-L-TiO 2 composite films have been studied using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), Thermogravimetric analysis (TGA), and Differential scanning calorimetry (DSC) analysis. The FTIR results and homogeneous, dense SEM images confirm the interaction of L-TiO 2 with the PBAT matrix. It has also been found that the addition of L-TiO 2 nanoparticles can increase the crystallinity, tensile strength, and thermal stability of PBAT. The addition of L-TiO 2 increased the tensile strength and decreased the elongation at break of films. The maximum tensile strength of the film, achieved with 5 wt% L-TiO 2 , was 47.0 MPa, compared with 24.3 MPa for pure PBAT film. The composite film with 5 wt% L-TiO 2 has outstanding oxygen and water vapor barrier properties. As the content of lignin-TiO 2 increases, the antimicrobial activity of the composite films also increases; the percentage of growth of all the tested bacteria Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli) is significantly reduced. Strawberries were packed to evaluate the suitability of produced composite films as packaging materials, as they effectively preserved pigments from accumulation and extended the shelf-life as compared to commercial polyethylene packaging film. • PBAT-lignin-TiO 2 composites were prepared using the melting and hot-pressing method. • The PBAT-lignin-TiO 2 composites exhibit enhanced hydrophobicity and higher barrier performance. • The composites have been found to possess acceptable levels of mechanical strength and antibacterial activity. • PBAT films containing L-TiO 2 were found to be effective in extending the shelf life of strawberries. [ABSTRACT FROM AUTHOR]

This study aims to understand the molecular and supramolecular transformations of wheat endosperm biopolymers during bread-making, and their implications to fabricate self-standing films from stale white bread. A reduction in the M w of amylopectin (51.8 × 106 vs 425.1 × 106 g/mol) and water extractable arabinoxylans WEAX (1.79 × 105 vs 7.63 × 105 g/mol), and a decrease in amylose length (245 vs 748 glucose units) was observed after bread-baking. The chain length distribution of amylopectin and the arabinose-to-xylose (A/X) ratio of WEAX remained unaffected during bread-making, suggesting that heat- or/and shear-induced chain scission is the mechanism responsible for molecular fragmentation. Bread-making also resulted in more insoluble cell wall residue, featured by water unextractable arabinoxylan of lower A/X and M w , along with the formation of a gluten network. Flexible and transparent films with good light-blocking performance (<30 % transmittance) and DPPH-radical scavenging capacity (~ 8.5 %) were successfully developed from bread and flour. Bread films exhibited lower hygroscopicity, tensile strength (2.7 vs 8.5 MPa) and elastic modulus (67 vs 501 MPa) than flour films, while having a 6-fold higher elongation at break (10.0 vs 61.2 %). This study provides insights into the changes in wheat biopolymers during bread-making and sets a precedent for using stale bread as composite polymeric materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Microalgae are emerging as a promising feedstock for bioplastics, with Chlorella vulgaris yielding significant amounts of starch. This polysaccharide is convertible into thermoplastic starch (TPS), a biodegradable plastic of industrial relevance. In this study, we developed a pilot-scale protocol for extracting and purifying starch from 430 g (dry weight – DW) of starch-enriched Chlorella vulgaris biomass. More than 200 g DW of starch were recovered, with an extraction yield and starch purity degree reaching 98 and 87 %, respectively. We have characterized this extracted starch and processed it into TPS using twin-screw extrusion and injection molding. Microalgal starch showed similar properties to those of native plant starch, but with smaller granules. We compared the mechanical properties of microalgal TPS with two controls, namely a commercial TPS and a TPS prepared from commercial potato starch granules. TPS prepared from microalgal starch showed a softer and more ductile behavior compared to the reference materials. This study demonstrates the feasibility of recovering high-purity microalgal starch at pilot scale with high yields, and highlights the potential of microalgal starch for the production of TPS using industrially relevant processes. [Display omitted] [ABSTRACT FROM AUTHOR]

• Biodegradable films/containers fabricated for plant seedling growth. • Pulp fiber and tannic acid introduced into the protein matrix. • 100 % germination when testing seeds of wheat, soybeans and mung beans. • Nutritious ions promoting root and leaf growth released from degraded bio-containers. Petroleum-based plastic containers for plant seedling growth are expensive to recycle and have negative environmental impacts when discarded. In this work, a novel family of sustainable and biodegradable plastic films and containers were fabricated by simply casting and mold-curing methods, which demonstrated outstanding performance promoting crop seed germination and plant seedling growth. Concentrate cottonseed protein (CPC) was used as polymeric matrix, pulp fiber (PF) as a physical reinforcement, tannic acid (TA) as a chemical modifying agent, with their addition contents ranging from 0 ∼ 30 % (PF) and 0 ∼ 10 % (TA), respectively. Evaluations of the composite CPC/PF and CPC/TA films regarding their structure, morphology, tensile properties, and water resistance show that the physical and chemical reinforcement resulted in good interfacial compatibility, mechanical strength, and water resistance. Moreover, the newly prepared bioplastics were biodegradable in soil in three weeks, and did not harm crop seed germination and growth. More importantly, the protein derived biocontainers/pot (CPC/PF30 and CPC/TA10) can provide excellent growth conditions for plant root and leaf growth such as chili peppers because of their low toxicity and 100 % germination rate. More importantly, the healthy growing environment was closely related to the presence of nutritious elements/ions that the plant needed. Specifically, the biodegradation of the bioplastics during plant seedling test released nitrogen-containing ions like NH 4 + (0.25 wt% for CPC/TA10 versus 0.17 wt% for polyethylene), and retained in soil, playing a decisive role in seedling growth. Therefore, the cottonseed protein bioplastics reinforced by pulp fiber and tannic acid are beneficial to crop seedling growth, holding great potential for being used as plantable pots/containers in agriculture and horticulture applications. [ABSTRACT FROM AUTHOR]

This study employs several approaches to enhance environmental sustainability: First, algal biomass (with 52.5% protein content) was converted into value-added products. Second, residual algal biomass from protein extraction and pigment extraction and raw algal biomass were used to manufacture bioplastics. Third, radiation shielding performance of bioplastics has been investigated. As an alternative to plastics originated from petroleum-based raw materials, environmentally friendly bioplastics were derived from residual algae biomass after extraction. The gamma-ray radiation shielding properties of the produced bioplastic have been investigated using WinXCOM theoretical calculation and GEANT4 Monte Carlo (MC) simulation. Fast neutron shielding performance of the considered materials also evaluated with help of theoretical calculation and the same MC simulation. The produced bioplastics are similar to ones with commercially available PLA polymer. Sample 1 was found to be better gamma-ray attenuator while Sample 2 has the highest value of the effective neutron removal cross section. Additionally, the boron addition has resulted in lower water absorption capacity in the prepared samples. Using algae to produce more than one product as a raw material source will be an effective step toward sustainable life, and they could be an alternative gamma-ray shielding material to existing commercial polymers. • Bioplastics were produced from Algal Biomass. • Characterization of the produced bioplastics are performed. • Radiation shielding capacities were evaluated for the first time. • The obtained shielding results are similar to commercial PLA polymer. [ABSTRACT FROM AUTHOR]

In the transition towards climate neutrality, biorefinery models are considered promising alternatives to processes based on fossil fuels and non-renewable materials. This consideration is attributed to the reduction of dependence on non-renewable systems, in line with greener and lower impact technological strategies. However, they imply a profound transformation of the production system, as the variable and stochastic nature of certain renewable sources makes it necessary to have various tools to provide flexibility and optimize the system. Their market penetration is currently limited by their level of development and the regulatory and financial support to implement the paradigm shift. Traditional linear production is still more economically viable compared to circular production models, based on efficiency parameters achieved by years of manufacturing experience. To reverse this trend, it is necessary to leverage its benefits through the use of appropriate assessment tools, as these are the ones that could drive the move towards biorefineries. This is the focus of this research report, which reviews various evaluation methodologies and indicators to effectively evaluate bio-based process schemes. Life Cycle Assessment (LCA), Product Environmental Footprint (PEF), Green Chemistry Principles (GCP), certification scheme requirements and Circular Economy Action Plans are reviewed and integrated into a precise assessment framework. To determine their effectiveness, three biorefinery models were evaluated: valorization of apple vinasses, grape must and chickpea peel. Through the combined analysis of bio-based scenarios, it has been possible to identify their benefits, bottlenecks and limitations, and to validate a comprehensive assessment framework that allows an accurate, effective and conscious analysis of bio-based models, promoting their development and market penetration. [Display omitted] • Bio-based process under a sustainability and circular approach • Use of indicators to evaluate the potential of bio-based alternatives. • Differences between PEF methodology and other LCA-based methods. • Proposition of a methodological combined framework under sustainable and circular perspectives. [ABSTRACT FROM AUTHOR]

• PHBH-made rigid packaging can be mesophilically digested, yielding 400 L-CH 4 /kg. • Size reduction of rigid packaging is needed and feasible with commercial shredders. • Successful co-digestion of PHBH with food waste, sewage sludge or swine manure. • PHBH was kinetically compatible with other organic waste. • Hydrogenotrophic methanogenesis was key in all co-digestion scenarios. This study evaluates the anaerobic mesophilic mono- and co-digestion of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) plastic bottles as a proxy for rigid packaging materials. Initial tests showed a 97.3 ± 0.2 % reduction in weight and an observable alteration in the surface (thinning, color fading and pitting) of the PHBH bottles after eight weeks. Subsequent tests showed that PHBH squares (3 × 3 cm) produced 400 NmL-CH 4 /g-VS fed , at a slower rate compared to powdered PHBH but with similar methane yield. Co-digestion experiments with food waste, swine manure, or sewage sludge showed successful digestion of PHBH alongside organic waste (even at a high bioplastic loading of 20 % volatile solids basis), with methane production comparable to or slightly higher than that observed in mono-digestion. Molecular analyses suggested that the type of co-substrate influenced microbial activity and that methane production was mainly driven by hydrogenotrophic methanogenesis. These results suggest the potential for integrating rigid PHBH packaging into anaerobic digesters. [ABSTRACT FROM AUTHOR]

Plastic pollution continuously accumulates in the environment and poses a global threat as it fragments into microplastics and nanoplastics that can harm ecosystems. To reduce the accumulation of microplastic and nanoplastic pollution, bioplastics made from biodegradable materials are promoted as a more sustainable alternative because it can degrade faster than plastics. However, plastics also leach out chemicals as they degrade and disintegrate, but the potential toxicity of these chemicals leaching out from plastics and especially bioplastics is poorly explored. Here, we determined the composition of leachates from plastics and bioplastics and tested their toxicity in Caenorhabditis elegans. LC-MS analysis of the leachates revealed that bioplastics leached a wider array of chemicals than their counterpart plastics. Toxicity testing in our study showed that the leachates from plastics and bioplastics reduced lifespan, decreased locomotion, and induced neurotoxicity in C. elegans. Leachates from bioplastics reduced C. elegans lifespan more compared to leachates from plastics: by 7%–31% for bioplastics and by 6%–15% for plastics. Leachates from plastics decreased locomotion in C. elegans more compared to leachates from bioplastics: by 8%–34% for plastics and by 11%–24% for bioplastics. No changes were observed in the ability of the C. elegans to respond to mechanical stimuli. The leachates induced neurotoxicity in the following neurons at varying trends: cholinergic neurons by 0%–53% for plastics and by 30%–42% for bioplastics, GABAergic neurons by 3%–29% for plastics and by 10%–23% for bioplastics, and glutamatergic neurons by 3%–11% for plastics and by 15%–29% for bioplastics. Overall, our study demonstrated that chemicals leaching out from plastics and bioplastics can be toxic, suggesting that both plastics and bioplastics pose ecotoxicological and human health risks. [Display omitted] • Bioplastics generally leached a wider array of chemicals than plastics. • Leachates from both plastics and bioplastics demonstrated toxicity in C. elegans. • The leachates reduced lifespan and decreased locomotion. • The leachates were toxic to cholinergic, GABAergic, and glutamatergic neurons. [ABSTRACT FROM AUTHOR]

Search for alternatives to synthetic plastics led to the development of eco-friendly degradable polymers of natural origin termed 'bioplastic' which is a sustainable option to reduce the reliance on fossil fuel resources and address the needs of pressing environmental problems. Food packaging has become an important aspect of supply chain management that not only governs the food from spoilage but also contributes to a sensible biocompatible material, safe for human consumption as there is a recent concern on microplastic leaching. Polyhydroxyalkanoates (PHAs), derived from microorganisms, are extensively used as a polymeric base for packaging applications in food industries as they offer advantages such as biodegradability, non-toxicity, hydrophobicity, thermoplasticity, and superior barrier properties, thereby making them a promising alternative to conventional synthetic plastics. However, challenges related to material properties, performance, and cost of the product must be addressed for PHA to make it an economical and feasible packaging material. Recent developments in PHA formulations in terms of technology, additives, and production factors have led to improvement in the polymer properties and beaconed the advent of active packaging. PHA-based packaging systems can redefine food industry packaging, turning it from a passive physical entity into an active solution that sustainably ensures food quality and safety. This review examines the sustainable microbial production of PHA from waste resources, recent advancements in PHA formulations, and their impact on material properties. It highlights emerging trends in active food packaging with PHA, such as controlled-release, antimicrobial and antioxidant properties, advanced barrier properties and spoilage indicators. [Display omitted] • Sustainable bio-production of PHA through microbial fermentation. • Strategies to enhance the PHA synthesis by microbial candidates are explored. • The emerging trends in active food packaging associated with PHA have been emphasized. • Safety and regulatory aspects of PHA-based packaging have been emphasized. [ABSTRACT FROM AUTHOR]

The pressing problem posed by plastic pollution has led to other, environmentally friendly alternatives, such as polyhydroxyalkanoates. This work proposes an innovative process to produce poly(3-hydroxybutyrate) by replacing expensive substrates, such as sugars, with methane. A two-step process was simulated: a first fermentation is performed in a continuous mode for 20 days to grow a strain belonging to the genus Methylocystis , while a second semi-continuous and nitrogen-limited fermentation is employed to induce the poly(3-hydroxybutyrate) accumulation within 12 days. The effects of the superficial gas velocity on the mass transfer and the poly(3-hydroxybutyrate) production yields were evaluated. Several scenarios were analyzed to optimize the geometry of the reactors and the methane utilization. The working volume of the reactors, as well as the presence of gas recycling stream, were shown to affect the global yields positively, while improving the aspect ratio from 8 to 19, with equal volume, lowered the fraction of poly(3-hydroxybutyrate) into the biomass by up to 37.5%. [Display omitted] • Methane is a valuable substrate for production of PHB. • Improving superficial gas velocity enhanced PHB production yield. • Internal gas recirculation saved methane. • Reactor geometry affected PHB production yield. • To parity of aspect ratio, larger volumes increased PHB production yield. [ABSTRACT FROM AUTHOR]

[Display omitted] Biogas-based biopolymer production represents an alternative biogas valorization route with potential to cut down plastic pollution and greenhouse gas emissions. This study investigated for the first time the continuous bioconversion of methane, contained in biogas, into poly(3-hydroxybutyrate) (PHB) by a mixed methanotrophic culture using an innovative high mass-transfer Taylor flow bioreactor. Following a hydrodynamic flow regime mapping, the influence of the gas residence time and the internal gas recirculation on CH 4 abatement was assessed under non nutrient limiting conditions. Under optimal operational conditions (gas residence time of 60 min and internal gas recycling ratio of 17), the bioreactor was able to support a CH 4 removal efficiency of 63.3%, a robust CH 4 elimination capacity (17.2 g-CH 4 m-3h-1) and a stable biomass concentration (1.0 g L-1). The simultaneous CH 4 abatement and PHB synthesis was investigated under 24-h:24-h nitrogen feast/famine continuous operation. The cyclic nitrogen starvation and the Taylor flow imposed in the bioreactor resulted in a relatively constant biomass concentration of 0.6 g L-1 with PHB contents ranging from 11 to 32% w w-1 (on a dry weight basis), entailing an average PHB productivity of 5.9 g-PHB m-3 d-1 with an associated PHB yield of 19.8 mg-PHB g-CH 4 -1. Finally, the molecular analysis of the microbial population structure indicated that type II methanotrophs outcompeted non-PHB accumulating type I methanotrophs, with a heterotrophic-methanotrophic consortium enriched in Methylocystis , Hyphomicrobium , Rubinisphaeraceae SH PL14 and Pseudonocardia. [ABSTRACT FROM AUTHOR]

Biopolymers based on starch, cellulose and proteins extracted directly from biomass with or without modification have been widely used as the natural resources to produce biodegradable plastic. Starch has several disadvantages: strong hydrophilic behavior and inferior mechanical properties when compared with synthetic polymers. Starch is also mostly soluble in water and will be decomposed before undergoing the gelatinization process. To provide resistance and mechanical strength of starch, several fillers (reinforcement) in the form of metal and natural materials are usually added to the polymer matrix. Zinc oxide (ZnO) nanoparticle and natural fiber as a lightweight material that is biocompatible, nontoxic, cost-effective and exhibit strong antibacterial activity can be considered as a reinforcement of starch-based bioplastic. The present study, the reinforcing effect of ZnO on the mechanical, antibacterial, and physical properties of bioplastic films in the form of cassava starch/chitosan/pineapple leaf fiber (PALF)/ZnO. The highest value of elongation at break is for 16 % ZnO-bioplastics which could be completely decomposed only 21 days in ordinary soil and only 18 days in seawater. The packaging tests using slice bread showed antimicrobial properties with no fungal growth for 30 days of bioplastic coatings with 10, 13, and 16 % ZnO NPs. The results in this study indicated that, the ZnO and PALF plays an important role in reinforcing the physical, mechanical, and antibacterial properties of starch/chitosan/PALF-based bioplastic. [ABSTRACT FROM AUTHOR]

This paper presents the results of an equivalence analysis of conventional and bio-based plastics based on a consumer study using Perceived Quality as a measure. The mass use of non-recyclable plastics poses an immense ecological problem. Due to their importance in consumer and industrial products, plastic use cannot be completely eliminated, however, bio-based alternatives are increasingly available. In order to strengthen the acceptance of these "bioplastics", especially in visible and tactile product areas, the sensory properties must be precisely determined and specified. [ABSTRACT FROM AUTHOR]

Background. Packaging materials are responsible for approximately 40% of the produced plastics while food packaging is the number one end user of such materials. Due to the diverse and extensive deleterious effects of conventional plastics on the environment, the food packaging industry is constantly seeking for new alternatives for such materials. Scope and approach. In an attempt to replace petroleum-based plastics and formulate a sustainable solution, new generation of plastic materials termed 'bioplastics' have been developed. The term bioplastic is mostly used to define plastics that can be either bio-based, biodegradable, or both. The current review explores the basic function of food packaging, various types of packaging, the required characteristics and possible processing techniques, and degradation routes of bioplastics. Moreover, the manuscript provides a broad overview of different types of bioplastics utilized in food packaging and their constituent biopolymers, highlighting their distinctive properties and functionalities in relation to their packaging applications. Key findings and conclusions. The food packaging is progressing fast in order to meet the world need for environmentally friendly and sustainable packaging material. These attempts are focused in various fronts which includes (i) improving the performance of natural biodegradable polymers using physical, chemical and enzymatic treatments, (ii) synthesizing new biodegradable polymers, improving the polymer characteristics, and scaling up the processes, (iii) improving the production of bio-based conventional polymers, and (iv) searching for new renewable sources. • Plastic packaging is accountable for ∼40% of produced plastics, when food packaging is the number one end user. • Food packaging is used in order to contain and protect products allowing convenient consumer experience and communication. • Bioplastic material can be referred as bio-based, biodegradable, or both. • Bioplastic development for food packaging is steadily growing increasing their use as opposed to conventional plastics. [ABSTRACT FROM AUTHOR]

Chemicals from packaging materials might be transferred into food resulting in consumer exposure. Identifying these migrated chemicals is highly challenging and crucial to perform their safety assessment, usually starting by the understanding of the chemical composition of the packaging material itself. This study explores the use of the Molecular Networking (MN) approach to support identification of the extracted chemicals. Two formulations of bioplastics were analyzed using Liquid Chromatography hyphenated to High-Resolution Mass Spectrometry. Data processing and interpretation using a conventional manual method was performed as a point of comparison to understand the power of MN. Interestingly, only the MN approach facilitated the identification of unknown chemicals belonging to a novel oligomer series containing the azelaic acid monomer. The MN approach provided a faster visualization of chemical families in addition to the highlight of unrelated chemicals enabling to prioritize chemicals for further investigation improving the safety assessment of packaging materials. • Molecular Network approach promising to improve safety assessment of food packaging. • Molecular Network approach accelerates identification of chemicals such as oligomers. • Molecular Network visualization underscores nodes that may require further attention. • Unknown chemicals identified only via Molecular Network approach such as azealic oligomers. [ABSTRACT FROM AUTHOR]

Fatty acid starch esters are potential candidates for obtaining hydrophobic starch-based materials. The objective was to evaluate thermoplastic bio-composites with stearic acid cassava starch esters (SAE) as matrices reinforced with micro fibrillated cellulose (MFC). SAE with 0.11 and 0.14 of DS and native cassava starch were processed with 5 % and 10 % MFC by extrusion and then thermo-compression to obtain bio-composite films. Performance of bio-composites as a function of the degree of substitution (DS) of starch esters and the content of MFC, was evaluated. Starch esterification reduced the crystalline phase and glass transition temperature of bio-composites, as confirmed by structural and thermal analysis. The increase of DS reduced the degradation temperature, which was compensated by adding MFC, favoring thermal stability. The hydrophobicity of films increased with the degree of starch esterification. Treatments with 0.14 DS formed stiffer and less tensile strength films. There was an increase in the modulus of elasticity and a reduction in elongation by increasing MFC. Fracture microscopy of films showed defects by incomplete starch melting and lack of interfacial adhesion with MFC caused by starch esterification. Starch esterification and MFC dispersion were determinants in the performance of bio-composites. In consequence, starch esterification with stearic acid reduces the compatibility with the MFC and, consequently, the performance of composites. [Display omitted] • Starch esters are obtained through the in situ activation of stearic acid with TosCl. • Stearic acid cassava starch esters produce hydrophobic cellulosic bio-composites. • Esterification influences the adhesion of starch with microfibrillated cellulose. [ABSTRACT FROM AUTHOR]

Poly(butylene adipate-co-terephthalate) (PBAT) is a biodegradable plastic that is difficult to degrade under both mesophilic and thermophilic anaerobic conditions. In this study, the impact of the thermo-alkaline pretreatment (48 h, 70 °C, 1 % w/v NaOH) on the anaerobic degradation (AD) of PBAT, poly(lactic acid) (PLA) and PBAT/PLA blended plastics was investigated. Under mesophilic conditions, pretreatment only improved the methane yield of PBAT/PLA/starch plastic (100 days, 51 and 34 NmL/g VS add for the treated and original plastics, respectively). Under thermophilic conditions, the pretreatment increased the methanogenic rate of PLA, PBAT and PBAT/PLA/starch plastic at the beginning stage (22 days, 35 and 79 NmL/g VS add for original and treated PBAT, respectively), but did not change the methane yield at the end of the incubation (100 days, 91 NmL/g VS add for original and treated PBAT). The reduction in the molecular weight and the formation of pore structures on the plastic surface accelerated the utilization of plastics by microorganisms. Furthermore, the pretreated plastics tend to form microplastics (MPs) with size predominantly below 500 µm (>90 %). The numbers of MPs dynamically changed with the degradation time. Several genera of bacteria showed specific degradation of biodegradable plastics under thermophilic conditions, including Desulfitibacter , Coprothermobacter , Tepidimicrobium , c_ D8A-2 and Thermacetogenium. The results suggest that more attention should be paid to the problem of MPs arising from the thermo-alkaline pretreatment. [Display omitted] • Thermo-alkaline pretreatment improved methane yield of PBAT under thermophilic AD. • PLA and aliphatic component in PBAT were preferentially degraded. • The molecular weight was reduced and pore structure was formed of treated plastics. • The pretreated plastics are more likely to form MPs with size less than 500 µm. [ABSTRACT FROM AUTHOR]

Traditional plastics reshaped the society thanks to their brilliant properties and cut-price manufacturing costs. However, their protracted durability and limited recycling threaten the environment. Worthy alternatives seem to be polyhydroxyalkanoates, compostable biopolymers produced by several microbes. The most common 3-hydroxybutyrate homopolymer has limited applications calling for copolymers biosynthesis to enhance material properties. As a growing number of researches assess the discovery of novel comonomers, great endeavors are dedicated as well to copolymers production scale-up, where the choice of the microbial carbon source significantly affects the overall economic feasibility. Diving into novel metabolic pathways, engineered strains, and cutting-edge bioprocess strategies, this review aims to survey up-to-date publications about copolymers production, focusing primarily on precursors origins. Specifically, in the core of the review, copolymers precursors have been divided into three categories based on their economic value: the costliest structurally related ones, the structurally unrelated ones, and finally various low-cost waste streams. The combination of cheap biomasses, efficient pretreatment strategies, and robust microorganisms paths the way towards the development of versatile and circular polymers. Conceived to researchers and industries interested in tackling polyhydroxyalkanoates production, this review explores an angle often underestimated yet of prime importance: if PHAs copolymers offer advanced properties and sustainable end-of-life, the feedstock choice for their upstream becomes a major factor in the development of plastic substitutes. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Nutrient stresses were applied to Cupriavidus necator growing on carbon dioxide. • Nitrogen starvation induced a PHB accumulation of 54% of total cell dry weight. • The carbon conversion yield into PHB reached a maximum of 85% under nitrogen stress. • Single-stage starvation was more effective than double-stages for PHB production. • Gas transfer enhancement in the fed-batch mode could improve the polymer yield. Cupriavidus necator is a facultative chemolithoautotrophic bacterium able to convert carbon dioxide into poly-3-hydroxybutyrate. This is highly promising as the conversion process allows the production of sustainable and biodegradable plastics. Poly-3-hydroxybutyrate accumulation is known to be induced by nutrient starvation, but information regarding the optimal stress conditions controlling the process is still heterogeneous and fragmentary. This study presents a comprehensive comparison of the effects of nutrient stress conditions, namely nitrogen, hydrogen, phosphorus, oxygen, and magnesium deprivation, on poly-3-hydroxybutyrate accumulation in C. necator DSM545. Nitrogen starvation exhibited the highest poly-3-hydroxybutyrate accumulation, achieving 54% of total cell dry weight after four days of nutrient stress, and a carbon conversion efficiency of 85%. The gas consumption patterns indicated flexible physiological mechanisms underlying polymer accumulation and depolymerization. These findings provide insights into strategies for efficient carbon conversion into bioplastics, and highlight the key role of C. necator for future industrial-scale applications. [ABSTRACT FROM AUTHOR]

The intracellular nature of microbial polyhydroxyalkanoates (PHAs) requires two main steps in their production: bioconversion and extraction. The most widely used method for recovering poly(3-hydroxybutyrate) (PHB) is solvent extraction. Traditional approaches involve the use of halogenated solvents, whose environmental and health hazards are well known. New alternatives advocate the use of sustainable agents, which can be an effective and economical choice. In this work, the bioconversion process of starch-based water into PHB by Cupriavidus necator DSM 545 was first scaled-up using previously optimized conditions. A statistical model was then developed to optimize the best conditions for polymer extraction using NaOH by response surface methodology with a central composite design. The optimized and validated conditions were: 0.05 M NaOH at 29.6 °C for 1 h, resulting in 87.31 ± 0.33 % polymer yield, 104.13 ± 2.22 % polymer purity and 104.76 ± 2.41 % polymer recovery. These conditions were validated for operation at three different biomass-to-NaOH concentrations: 5.7 g/L, 20 g/L and 79.5 g/L, and scaled-up without sacrificing polymer yield, with high levels of PHB purity and recovery. In addition, this work proposed an approach for the scale-up of a halogen-free process for PHB extraction using NaOH, considering parameters that can be easily integrated into the common ranges used in the industry. [Display omitted] • PHB production by Cupriavidus necator DSM 545 using potato wastewater is scaled. • NaOH solution could be a sustainable and cost-effective method for PHA extraction. • PHB extraction is performed using the lowest concentration of the halogen-free agent. • Optimal conditions for PHB extraction are 0.05 M NaOH at 29.6 °C for 1 h. • NaOH extraction yields a polymer with a purity of over 99%. [ABSTRACT FROM AUTHOR]

The use of plastics has become deeply ingrained in our society, and there are no indications that its prevalence will decrease in the foreseeable future. This article provides a comprehensive overview of the global plastic waste disposal landscape, examining it through regional perspectives, various management technologies (dumping or landfilling, incineration, and reuse and recycling), and across different sectors including agriculture and food, textile, tourism, and healthcare. Notably, this study compiles the findings on life-cycle carbon footprints associated with various plastic waste management practices as documented in the literature. Employing the bio-circular-green economy model, we advocate for the adoption of streamlined and sustainable approaches to plastic management. Unique management measures are also discussed including the utilization of bioplastics combined with smart and efficient collection processes that facilitate recycling, industrial composting, or anaerobic digestion. Moreover, the integration of advanced recycling methods for conventional plastics with renewable energy, the establishment of plastic tax and credits, and the establishment of extended producer responsibility are reviewed. The success of these initiatives relies on collaboration and support from peers, industries, and consumers, ultimately contributing to informed decision-making and fostering sustainable practices in plastic waste management. [Display omitted] • Plastic waste management incorporated with bio-circular-green economy is discussed. • Global plastic recycling in different supply chains is examined. • Recycling methods including advanced integrated chemical recycling are analyzed. • Lifecycle carbon footprints of different waste management practices are summarized. • Pathways to decarbonize plastic waste recycling for carbon neutrality are proposed. [ABSTRACT FROM AUTHOR]

Free-standing films ha v e been obtained by drop-casting cellulose-glycerol mixtures (up to 50 wt% glycerol) dissolved in trifluoroacetic acid and trifluoroacetic anhydride (TFA:TFAA, 2:1, v:v). A comprehensive examination of the optical, structural, mechanical, thermal, hydrodynamic, barrier, migration, greaseproof, and biodegradation characteristics of the films was conducted. The resulting cellulose-glycerol blends exhibited an amorphous molecular structure and a reinforced H-bond network, as evidenced by X-ray diffraction analysis and infrared spectroscopy, respectively. The inclusion of glycerol exerted a plasticizing influence on the mechanical properties of the films, while keeping their transparency. Hydrodynamic and barrier properties were assessed through water uptake and water vapor/oxygen transmission rates, respectively, and obtained values were consistent with those of other cellulose-based materials. Furthermore, overall migration levels were below European regulation limits, as stated by using Tenax® as a dry food simulant. In addition, these bioplastics demonstrated good greaseproof performance, particularly at high glycerol content, and potential as packaging materials for bakery products. Biodegradability assessments were carried out by measuring the biological oxygen demand in seawater and high biodegradation rates induced by glycerol were observed. • TFA:TFAA solves cellulose and glycerol, forming amorphous films after solvent evaporation. • Glycerol addition plasticizes the films, maintaining transparency. • Glycerol enhances grease resistance while keeping low migration levels. • High biodegradation in seawater indicates the environmental friendliness of blends. [ABSTRACT FROM AUTHOR]

• Effects of PLA-MPs were assessed using both biochemical and behavioral endpoints. • PLA-MPs exposure induced a slight alteration on both oxidative stress and energetic biomarkers. • The higher concentration tested induced an alteration on the swimming activity. The accumulation of plastics waste in the environment has raised a worrisome concern, moving the society to seek out for sustainable solutions, such as the transition from the use of fossil-based, conventional plastics to bioplastics (BPs). However, once in the environment bioplastics have the same probability to accumulate and experience weathering processes than conventional plastics, leading to the formation of microplastics (MPs). However, to date the information on the potential toxicity of MPs originated from the weathering of bioplastics is limited. Thus, this study aimed at investigating the adverse effects induced by the exposure to MPs made of a bioplastic polymer, the polylactic acid (PLA), towards the freshwater cladoceran Daphnia magna. Organisms were exposed for 21 days to three concentrations (0.125 µg/mL, 1.25 µg/mL and 12.5 µg/mL) of PLA microplastics (hereafter PLA-MPs). A multi-level approach was performed to investigate the potential effects through the biological hierarchy, starting from the sub-individual up to the individual level. At the sub-individual level, changes in the oxidative status (i.e., the amount of reactive oxygen species and the activity of antioxidant and detoxifying enzymes) and oxidative damage (i.e., lipid peroxidation) were explored. Moreover, the total caloric content as well as the content of protein, carbohydrate and lipid content assess were used to investigate the effects on energy reserves. At individual level the changes in swimming activity (i.e., distance moved and swimming speed) were assessed. Our results showed that the exposure to PLA-MPs induced a slight modulation in the oxidative status and energy reserves, leading to an increase in swimming behavior of treated individuals compared to control conspecifics. These results suggest that the exposure to MPs made of a bioplastic polymer can induce adverse effects similar to those caused by conventional polymers. [ABSTRACT FROM AUTHOR]

Bioplastics are considered sustainable alternatives to conventional microplastics which are recognized as a threat to terrestrial ecosystems. However, little is known about the potential ecotoxicological effects of bioplastics on soil fauna and ecosystems. The present study assessed the toxicity of microplastics [Polystyrene (PS), Polyethylene (PE)] and bioplastics [Polyvinyl alcohol (PVA), Sodium polyacrylate (NaPa) on a key soil fauna Oppia nitens , a soil oribatid mite, and investigated the ecological relevance of O. nitens avoidance response as a valuable tool for the risk assessment of contaminated soils such as the Superfund sites. Findings showed that the mites' net response indicated avoidance behavior such that in most cases as concentrations of micro- and bioplastics increased, so did the avoidance responses. The avoidance EC 50 endpoints showed PS < PE < PVA < NaPa, indicating higher deleterious effects of microplastics. High toxicity of PS in soils to O. nitens at EC 50 of 165 (±25) mg/kg compared to bioplastics and other known contaminants poses an enormous threat to soil. For bioplastics in this study, there were no significant avoidances at concentrations up to 16,200 mg/kg compared to PS and PE which showed avoidance responses at 300 and 9000 mg/kg respectively, implying that bioplastics might be relatively safer to soil mites compared to conventional microplastics. Also, results indicated that long-term heavy metal pollution such as in contaminated Superfund sites decreased microbial biomass; a useful bioindicator of soil pollution. Furthermore, O. nitens avoidance of heavy metals contaminated sites demonstrated the ecological relevance of avoidance response test when assessing the habitat integrity of contaminated soil. The present study further supports the inclusion of the oribatid mite, O. nitens in the ecological risk assessment of contaminants in soil. [Display omitted] • Reduced microbial biomass reported in Superfund heavy metal-contaminated sites. • O. nitens preference of contaminant-free soils poses risks to soil ecosystem services. • Soil mites tolerate bioplastics better than microplastics in standard artificial soil. • O. nitens avoidance of Superfund sites support its relevance in soil risk assessments. [ABSTRACT FROM AUTHOR]

Development of renewable and biodegradable plastics with good properties, such as the gas barrier, UV-shielding, solvent resistance, and antibacterial activity, remains a challenge. Herein, cellulose/ZnO based bioplastics were fabricated by dissolving cellulose carbamate in an aqueous solution of NaOH/Zn(OH) 4 2−, followed by coagulation in aqueous Na 2 SO 4 solution, and subsequent hot-pressing. The carbamate groups detached from cellulose, and ZnO which transformed from cosolvent to nanofiller was uniformly immobilized in the cellulose matrix during the dissolution/regeneration process. The appropriate addition of ZnO (below 10.67 wt%) not only improved the mechanical properties but also enhanced the water and oxygen barrier properties of the material. Additionally, our cellulose/ZnO based bioplastic demonstrated excellent UV-blocking capabilities, increased water contact angle, and enhanced antibacterial activity against S. aureus and E. coli , deriving from the incorporation of ZnO nanoparticles. Furthermore, the material exhibited resistance to organic solvents such as acetone, THF, and toluene. Indeed, the herein developed cellulose/ZnO based bioplastic presents a promising candidate to replace petrochemical plastics in various applications, such as plastic toys, anti-UV guardrails, window shades, and oil storage containers, offering a combination of favorable mechanical, gas barrier, UV-blocking, antibacterial, and solvent-resistant properties. [Display omitted] [ABSTRACT FROM AUTHOR]

Emerging industries and technologies are made up of objective, practical requirements and ideas that encompass broad hopes for what future newness might enable. The bioeconomy is one such emerging industry. Its recent evolution has involved a complicated and dynamic mix of promises, reality checks and subsequent ambivalences. This article frames and investigates the emerging algae-based bioplastics industry as one niche within this broader system envisaged for social, technological, economic, political and ecological change. As such, our paper presents two categories of knowledge that in practice interrelate: 1) specific and practical recommendations that can assist a future algal-based bioplastics industry to develop in Australia in ways that are conscious of socio-ecological and socio-cultural dimensions, and 2) critical extensions that go beyond the attributes of newness, impact, suddenness and universality often emphasised in both popular and scientific research into emerging green technologies. In particular, our analysis highlights the importance of specific temporal, tonal and spatial factors when framing the contextual factors associated emerging industries, technologies and the different pathways for change they might help support. • Pathways and enabling factors for a algal-based bioplastics industry in regional Australia are presented. • The 'social idea' of the bioeconomy is analysed with reference to algal-based bioplastics. • The algal-based bioplastics industry is contextualised in relation to transition pathways literatureon the bioeconomy. • Themes and recommendations are synthesised from literature review and semi-structured interviews. [ABSTRACT FROM AUTHOR]

Microalgae show great promise as sources of starch, one of the most widely consumed macromolecules. In this study, we evaluated the impact of three starch-inducing factors, namely nitrogen deprivation, supra-optimal temperature, and red light, on the physiology and starch accumulation capacity of Chlorella vulgaris. This starch accumulation was monitored by measuring the total carbohydrate content and transmission electron microscopy (TEM) imaging. Nitrogen deprivation and a supra-optimal temperature of 39 °C resulted in carbohydrate contents of 69.7 and 64.3 % of dry weight (DW) respectively. This constituted a 5.3- and 3.3-fold increase in carbohydrate productivity compared to the control, after 4 days of cultivation. During this period, carbohydrates represented over 80 % of the produced material (DW basis). However, nitrogen deprivation and supra-optimal temperature were accompanied by extensive stress, leading to lower cell division rates and damage to the photosynthetic apparatus. Red light illumination resulted in a more moderate production of carbohydrates. After 4 days of cultivation, the carbohydrate content reached 46.8 %, representing a 3.0-fold increase in productivity compared to control. The composition of the starch formed under red light was surprisingly poor in amylose, similar to transitory-type starch rather than storage starch. Most notably, the starch accumulation under red light was sustained over 7 days without affecting the rate of cell division and quantum yield efficiency. To the best of our knowledge, red light is the only factor reported so far to induce a significant starch accumulation without hindering cell division and photosynthesis efficiency, even after long-term exposure (7 days). Furthermore, all three conditions induced a cell wall thickening, albeit without affecting the recovery of accumulated starch by high-pressure homogenization. These results highlight the potential of red light as a starch inducer in Chlorella vulgaris and open up perspectives for the production of starch-based bioplastics from microalgae. [Display omitted] • Chlorella vulgaris CCALA924 was grown in an incubator with a 16-h light/8-h dark period. • Red light promoted starch accumulation, maintaining cell division and photosynthesis capacity. • Nitrogen deprivation resulted in the highest starch accumulation overall. • A supra-optimal temperature of 39 °C severely impaired microalga growth. • Cell wall thickening occurred for all inducers without hindering cell rupture. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHA) are bioplastics of growing interest due to their potential use in specialized applications obtained from renewable sources as low-cost raw materials. This study shows the effects of some operational variables affecting the PHA production via solid-state fermentation (SSF) using brewer's spent grain (BSG) and Burkholderia cepacia at lab-scale (0.5 L) and a first assessment of the process at higher scales. Temperature, pH, moisture content (MC), and sugar beet molasses (SBM) addition significantly affected the PHA production performance. From the lab-scale evaluated scenarios, the highest PHA production was 13.1 mg per gram of dry BSG when adding 30% SBM, at 70% MC, 30 °C and pH 5.5. PHA production was also tested at 3 L and 5 L using not-isolated and near-adiabatic bioreactors, respectively. At those scales, the maximum production was 9.5 mg per gram of dry BSG (0.13 g per kg per h), showing promising results towards future developments of SSF for PHA production. [ABSTRACT FROM AUTHOR]

• Aerobic and anaerobic degradability of biocomposite smart cellphone cases conducted. • Aerobic degradability was studied at laboratory- and field-scale. • Cellphone cases with 35% biobased content/flax degraded by 20% in composting (58C). • Cellphone cases degraded by only 6–8% in anaerobic digestion (37–55C). • Cellphone case size did not affect degradation rate due to low biobased content. The increase in production of biobased plastics as a replacement for fossil fuel-based plastics has created the need for studies to assess their degradation under various conditions. However, developing reliable laboratory and field-testing protocols for biobased materials and products still requires extensive research. In this study, the biodegradability of a biocomposite consumer product, smart cellphone case, was determined under laboratory scale anaerobic (38 °C) and composting assays (58 °C) as well as under field scale (60–67 °C) composting conditions. The laboratory scale composting assay was conducted for 46 days using cellphone cases with dimensions of 7 × 3.5 × 0.2 and 4.6 × 3.5 × 0.2 cm, which achieved approximately 20% biodegradation. The field scale composting conditions achieved 55% weight loss of cellphone cases in 80 days. The subsequent anaerobic biodegradation assays contained three different sized (grinded, cut into 2 × 2 × 0.2 and 4 × 4 × 0.2 cm pieces) biocomposite cellphone cases conducted under mesophilic conditions for 169 days. Among the conditions tested, the size of cellphone cases did not cause a significant difference in biodegradation under anaerobic conditions. Anaerobic digestion conditions yielded only 6–8% biodegradation, which was significantly lower than that of composting. The results agree with literature on conventional waste streams stating that aerobic microbial processes are more effective to break down complex substrates, similar to biocomposite cellphone cases tested, than their anaerobic counterparts. [ABSTRACT FROM AUTHOR]

[Display omitted] • The impact of biomass withdrawal strategy is compared in MMCs for PHA production. • Biomass withdrawal at the end of the famine led to higher global PHA productivity. • Biomass withdrawal at the end of the feast requires a smaller accumulation reactor. • Global PHA productivity is highly dependent on volumetric biomass productivity. The production of polyhydroxyalkanoates (PHA) by mixed microbial cultures (MMC) has been studied as an alternative to pure cultures in order to reduce the price of PHA through use of open systems and low-cost substrates, such as agro-industrial sub-products. However, the widespread applicability of this process depends on the optimization of operational factors impacting PHA productivity. This study addresses the impact of biomass withdrawal strategy on the performance of MMC selection reactors and consequently on biomass productivity and global PHA productivity. Two selection reactors were operated in parallel under similar conditions, except for the timing of biomass withdrawal, at the end of the famine phase (Reactor 1, R1) versus at the end of the feast phase (Reactor 2, R2) at an organic loading rate of 100 Cmmol.L−1.d−1 and solids retention time of 4 days. The biomass selected in both conditions had similar PHA storing capacity as shown by the similar yields of PHA per substrate obtained in the accumulation assays; however, R1 reached a higher biomass productivity (about 4-fold higher than R2). This study demonstrated that removing the excess biomass at the end of the famine phase resulted in a much higher global PHA productivity and that the key parameter affecting the global PHA productivity of the 2-stage system was the volumetric biomass productivity. Results obtained provide important insight into how MMC systems can be best operated to maximize PHA productivity. [ABSTRACT FROM AUTHOR]

The demand for the production of biodegradable plastics has significantly increased. Bioplastics have become an essential alternative to the threats of the daily consumable plastics, sourced from fossil fuels, to the environment. Polyhydroxyalkonates (PHAs) are a ubiquitous group of bioderived and biodegradable plastics, however their production is limited by the costs associated mainly with the carbon sources. Herein, this study aims to reduce the PHAs production cost by using a by-product from the dairy industry, i.e. , cheese whey (CW), as a sole carbon source. The developed process recruits an aquatic isolate, Bacillus flexus Azu-A2, and is optimized via studying various parameters using the shaking flasks technique. The results showed that the maximum PHA production (0.95 g L-1) and PHA content (20.96%, w/w), were obtained after incubation period 72 h at 45 °C, 100 rpm agitation rate, 50% CWS concentration, pH 8.5, and 1.0 g L-1 ammonium chloride. Physiochemically, Fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectroscopy (GC–MS), nuclear magnetic resonance (NMR), and energy-dispersive X-ray (EDX) techniques, emphasized the type of the extracted PHA as polyhydroxybutyrate (PHB). The thermal properties of PHB were measured using differential scanning calorimetry (DSC), recording melting transition temperature (Tm) at 170.96 °C. Furthermore, a scanning electron microscope (SEM) visualized a homogenous microporous structure for the thin PHB biofilm. In essence, this study highlights the ability of Bacillus flexus Azu-A2 to produce a good yield of highly purified PHB at reduced production cost from dairy CW. Consequently, the current study paves the way for an improved whey management strategy. [Display omitted] [ABSTRACT FROM AUTHOR]

The agro-food industry produces huge amounts of wastes and by-products with high levels of carbohydrates and proteins, basic food groups that, properly treated, can be employed for the development of bioplastics. These high added-value products represent an alternative to traditional polymers. In this research work, rice bran was mixed with glycerol and water obtaining homogeneous blends which then are processed into bioplastics via injection moulding. The mixing temperature aids starch plastification and thus, affects the properties of the final specimens. In this way, the mechanical characterization revealed improvements for the highest temperature (110 °C) used which, at the same time, exhibited poor physical integrity during water immersion. Although the mechanical properties of the dried system obtained at 80 °C are slightly inferior to those obtained for the non-dried 110 °C system, these specimens are considered more adequate since they exhibited higher physical integrity and, consequently, better operating conditions. • Rice bran is a suitable raw material for the development of bioplastics. • Though water is required for starch plastification, excess water hinders processing. • The proper mixing temperature to produce balanced bioplastics is 80 °C. [ABSTRACT FROM AUTHOR]

In modern decades, an increase in environmental awareness has attracted the keen interest of researchers to investigate eco-sustainable, recyclable materials to minimize reliance on petroleum-based polymeric compounds. Poly (3-hydroxybutyrate) is amorphous, linear, and biodegradable bacterial polyesters that belong to the polyhydroxyalkanoates family with enormous applications in many fields. The present review provides comprehensive information on polyhydroxybutyrate production from different biomass feedstock. Various studies on PHB production by genetically engineered bacterial cells and optimization of parameters have been discussed. Recent technological innovation in processing polyhydroxybutyrate-based biocomposite through the different process has also been examined. Besides this, the potential applications of the derived competent biocomposites in the other fields have been depicted. [Display omitted] • Polyhydroxybutyrate production from biomass feedstock and microbial genetic modification • Processing techniques for the fabrication of polyhydroxybutyrate based polymer composites • Biodegradability studies of polymer composites [ABSTRACT FROM AUTHOR]

Due to their excellent properties, polyhydroxyalkanoates are gaining increasing recognition in the biodegradable polymer market. These biogenic polyesters are characterized by high biodegradability in multiple environments, overcoming the limitation of composting plants only and their versatility in production. The most consolidated techniques in the literature or the reference legislation for the physical, chemical and mechanical characterisation of the final product are reported since its usability on the market is still linked to its quality, including the biodegradability certificate. This versatility makes polyhydroxyalkanoates a promising prospect with the potential to replace fossil-based thermoplastics sustainably. This review analyses and compares the physical, chemical and mechanical properties of poly-β-hydroxybutyrate and poly-β-hydroxybutyrate-co-β-hydroxyvalerate, indicating their current limitations and strengths. In particular, the copolymer is characterised by better performance in terms of crystallinity, hardness and workability. However, the knowledge in this area is still in its infancy, and the selling prices are too high (9–18 $ kg−1). An analysis of the main extraction techniques, established and in development, is also included. Solvent extraction is currently the most widely used method due to its efficiency and final product quality. In this context, the extraction phase of the biopolymer production process remains a major challenge due to its high costs and the need to use non-halogenated toxic solvents to improve the production of good-quality bioplastics. The review also discusses all fundamental parameters for optimising the process, such as solubility and temperature. [Display omitted] • PHB and PHBV characterization approaches have been reported. • PHB and PHBV properties have been compared to fossil-based plastics. • Biopolymer extraction processes have been discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The method was successfully developed through the exploration of four combinations. • These combinations involved two distinct solvents and two different biopolymers. • FTIR PHA quantification method can accurately measure PHA production from MMC. • FTIR spectra absorbance based on the main chain of PHA. • Liquid cell enhance the application of FTIR as a biopolymer measurement. Polyhydroxyalkanoate (PHA) is a family of naturally-occurring biopolymers synthesized by more than 300 microorganisms in the environment. These biopolymers have been investigated as a source material to substitute fossil fuel-based polymers; hence the synthesis of biopolymers and their characterization is a critical step in optimizing the process. Because of this, the biological production of PHA using PHA-producing microorganisms is currently the dominating process; however, the use of microbial mixed culture (MMC), such as wastewater sludge, is gaining attention. Different than pure cultures, MMC has higher culturing condition tolerance since the complex species composition and is easily obtained from wastewater treatment plants, which shortens the culturing time, lowers the cost, and promotes the application. The main constraint in MMC-based PHA is the extraction and quantification of PHA from the more complex matrix. In this paper, Fourier-transform infrared (FTIR) spectroscopy is evaluated to be used as a quantification method of PHA in MMC systems. Firstly, commercially available analytical standards, which consist of PHA/PHB, and two different solvents (chloroform and dichloromethane), were used and tested by this method, with KBr card and liquid cell methods, and the results are validated by gas chromatography mass spectrometry (GC/MS). The method was then tested using 12 samples from wastewater treatment plants. The PHA content in biomass varied from 3.42 w/w% to 1.22 w/w% following extraction with chloroform as solvent as determined by this method. In the four different combination standards, the best one is consisted of PHB and chloroform, and FTIR-liquid cell showed higher promise for PHA quantification in complex matrices. [ABSTRACT FROM AUTHOR]

Climate change and plastic pollution are likely the most relevant challenges for the environment in the 21st century. Developing cost-effective technologies for the bioconversion of methane (CH 4) into polyhydroxyalkanoates (PHAs) could simultaneously mitigate CH 4 emissions and boost the commercialization of biodegradable polymers. Despite the fact that the role of temperature, nitrogen deprivation, CH 4 :O 2 ratio or micronutrients availability on the PHA accumulation capacity of methanotrophs has been carefully explored, there is still a need for optimization of the CH 4 -to-PHA bioconversion process prior to becoming a feasible platform in future biorefineries. In this study, the influence of different cultivation broth pH values (5.5, 7, 8.5 and 10) on bacterial biomass growth, CH 4 bioconversion rate, PHA accumulation capacity and bacterial community structure was investigated in a stirred tank bioreactor under nitrogen deprivation conditions. Higher CH 4 elimination rates were obtained at increasing pH, with a maximum value of 50.4 ± 2.7 g CH 4 ·m−3·h−1 observed at pH 8.5. This was likely mediated by an increased ionic strength in the mineral medium, which enhanced the gas-liquid mass transfer. Interestingly, higher PHB accumulations were observed at decreasing pH, with the highest PHB contents recorded at a pH 5.5 (43.7 ± 3.4 %w·w−1). The strong selective pressure of low pH towards the growth of Type II methanotrophic bacteria could explain this finding. The genus Methylocystis increased its abundance from 34 % up to 85 and 90 % at pH 5.5 and 7, respectively. On the contrary, Methylocystis was less abundant in the community enriched at pH 8.5 (14 %). The accumulation of intracellular PHB as energy and carbon storage material allowed the maintenance of high CH 4 biodegradation rates during 48 h after complete nitrogen deprivation. The results here obtained demonstrated for the first time a crucial and multifactorial role of pH on the bioconversion performance of CH 4 into PHA. [Display omitted] • Low pH (5.5–7.0) is a strong selective pressure towards the growth of Methylocystis. • A higher abundance of Methylocystis entails higher PHA accumulation (>40 %w·w−1). • High pH (8.5) boosts the CH 4 degradation performance (>50 g CH 4 ·m−3·h−1). • Very high pH (10) supported a negligible biomass growth and induced cell lysis. • PHA accumulation started immediately after nitrogen deprivation (<10 mg N·L−1). [ABSTRACT FROM AUTHOR]

Plastic pollution has become a major global concern, posing numerous challenges for the environment and wildlife. Most conventional ways of plastics degradation are inefficient and cause great damage to ecosystems. The development of biodegradable plastics offers a promising solution for waste management. These plastics are designed to break down under various conditions, opening up new possibilities to mitigate the negative impact of traditional plastics. Microbes, including bacteria and fungi, play a crucial role in the degradation of bioplastics by producing and secreting extracellular enzymes, such as cutinase, lipases, and proteases. However, these microbial enzymes are sensitive to extreme environmental conditions, such as temperature and acidity, affecting their functions and stability. To address these challenges, scientists have employed protein engineering and immobilization techniques to enhance enzyme stability and predict protein structures. Strategies such as improving enzyme and substrate interaction, increasing enzyme thermostability, reinforcing the bonding between the active site of the enzyme and substrate, and refining enzyme activity are being utilized to boost enzyme immobilization and functionality. Recently, bioengineering through gene cloning and expression in potential microorganisms, has revolutionized the biodegradation of bioplastics. This review aimed to discuss the most recent protein engineering strategies for modifying bioplastic-degrading enzymes in terms of stability and functionality, including enzyme thermostability enhancement, reinforcing the substrate binding to the enzyme active site, refining with other enzymes, and improvement of enzyme surface and substrate action. Additionally, discovered bioplastic-degrading exoenzymes by metagenomics techniques were emphasized. [Display omitted] • Conventional recycling methods could be replaced by biological ones that offer an ecosystem-friendly approach. • The aerobic and anaerobic mechanisms of microbial degradation for bioplastic have been reviewed. • The stability and activity of extracellular microbial enzymes can be influenced by environmental factors. • The preparation of bioplastic-degrading enzymes in various microorganisms using metagenomics techniques has been discussed. • Protein engineering techniques of bioplastic-degrading enzymes have been emphasized to improve biocatalytic performance. [ABSTRACT FROM AUTHOR]

A growing number of studies have demonstrated that microplastic (MP) contamination is widespread in terrestrial ecosystems. A wide array of MPs made of conventional, fossil-based polymers differing in size and shape has been detected in soils worldwide. Recently, also MPs made of bioplastics have been found in soils, but there is a dearth of information concerning their toxicity on soil organisms. This study aimed at exploring the potential toxicity induced by the exposure for 28 days to irregular shaped and differently sized MPs made of a fossil-based (polyethylene terephthalate – PET) and a bioplastic (polylactic acid – PLA) polymer on the earthworm Eisenia foetida. Two amounts (1 g and 10 g/kg of soil, corresponding to 0.1% and 1% of soil weight) of both MP types were administered to the earthworms. A multi-level approach was used to investigate the MP-induced effects at sub-individual and individual level. Changes in the activity of antioxidant and detoxifying enzymes, as well as in lipid peroxidation levels, were investigated at specific time-points (i.e., 7, 14, 21 and 28 days) as sub-individual responses. Histological analyses were performed to assess effects at tissue level, while the change in digging activity was considered as a proxy of behavioral effects. Earthworms ingested MPs made of both the polymers. MPs made of PET did not induce any adverse effect at none of the biological levels. In contrast, MPs made of PLA caused the modulation of earthworms' oxidative status as showed by a bell-shaped activity of superoxide dismutase coupled with an increase in glutathione peroxidase activity. However, neither oxidative and tissue damage, nor behavioral alteration occurred. These findings suggest that the exposure to bio-based MPs can cause higher toxicity compared to fossil-based MPs. [Display omitted] • Microplastics (MPs) made of fossil-based or bioplastic polymers were ingested by earthworms. • MPs made of polylactic acid (PLA) altered the oxidative status of earthworms. • MPs made of Polyethylene terephthalate (PET) did not induce biochemical effects. • No effects at tissue level and behaviour were induce by both microplastics types. [ABSTRACT FROM AUTHOR]

Keratin was synthesized by alkaline hydrolysis from chicken feathers and then continue by casting method for producing bioplastics with additional various amounts of chitosan as a filler, polyvinyl alcohol (PVA) and glycerol as a plasticizer. The main purpose is analysis the effect of chitosan on the structural properties using quantitative analysis of X-ray diffraction (XRD) spectra, chemical bonding by Fourier transforms infrared (FTIR) spectra, and mechanical properties by texture analyser to the keratin-based bioplastics. Biodegradation of bioplastics was analysed from the loss of weight by burying in the soil. It's found that, the additional of chitosan (0 %, 2 %, 5 %, and 8 %) increased the crystallinity of bioplastics by 11.83 %, 11.12 %, 18.99 %, and 17.03 %, respectively, but decreasing tensile strength and elasticity of bioplastics. Degradation of bioplastic keratin-based shows that the addition of chitosan can reduce the degradation time which is directly proportional to the loss of C O bonds. The highest degradation rate is 89.29 % in 49 days for keratin-based bioplastics with 8 % chitosan, indicated that high potential for future production. [ABSTRACT FROM AUTHOR]

Currently, mussel farming uses of traditional plastic nets that accumulate on beaches and on the seabed in the event of breakage and accidental dispersion, contributing to the marine litter issue. An attempt is being made to replace the polypropylene nets with alternative materials to make the aquaculture full production cycle more sustainable. However, alternative materials need to be characterised both functionally and environmentally. This article describes a characterisation study in which plastic materials were exposed for approximately three years to the marine environment in a bay dedicated to mussel farming to provide data on the degradation behaviour of the selected polymers for eco-design purposes. Samples of the different materials, in the form of 3-mm thick dumbbells, were placed on the seabed at a depth of 12 m and in the water column at 2 m below the sea surface. At different time periods (after 6, 15, 24, 32 months), the samples were recovered, their mass and thickness were measured, and the mechanical properties were characterised. The results lead to the identification of some materials as sufficiently resistant to deterioration and therefore possible candidates for the application. Other materials generally used to make bags and films showed a very fast degradation and therefore do not seem to meet the performance requirements for mussel farming. The methodology used in this study seems suitable for conducting long-term exposure tests on locations of interest and collecting specific data for eco-design purposes before the application of the product on the markets. • Five biodegradable materials were tested in the sea for mussel socks application. • Mass, thickness, and mechanical properties were measured over a period of 32 months. • Tested materials showed faster degradation at the seabed, rather than in the water column. • Four biodegradable materials showed too fast degradation for mussel farming. • One biodegradable material seems to be the most promising for mussel farming. [ABSTRACT FROM AUTHOR]

Kitchen waste (KW) production is anticipated to rise because of accelerated urban and economic growth, particularly in Asian nations. Therefore, applications/recycling of KW should be explored for its effective utilization to generate a sustainable source of energy that will ultimately avoid massive economic and energy losses. The main goal of this study was to investigate the combinational effect of thermochemical and enzymatic pre-treatment on synthetic KW to enhance the release of fermentable sugars for the synthesis of value-added products such as polyhydroxyalkanoates (PHAs). The thermochemical pre-treatment of KW samples was performed using 4 N HCl, 4 N H 2 SO 4 , and 4 N NaOH at a concentration of 0–30% (v/v), 30–100 °C for 0–120 min. Furthermore, to enhance the total fermentable sugars, variable enzyme dosages were added after acidic or alkaline pre-treatments (0–1% v/v α-amylase and 0–1% v/v amyloglucosidase-AMG) while maintaining a constant pH 5, temperature 50 °C, and time 30 min. Pre-treatment of KW with acid (15% v/v 4 N HCl in water) at temperature 100 °C, followed by enzymatic hydrolysis, i.e., 0.6% (v/v) α-amylase and 0.4% (v/v) amyloglucosidase (at pH 5, 50 0C and 60 min) resulted in the maximum concentration of fermentable reducing sugars (46.13 g/L) in the hydrolysate. • The food and fuel conflict can be resolved using KW for valuable product synthesis. • This research contributes to an improved comprehension of PHA production using KW. • Combined thermochemical and enzymatic pre-treatment maximized the reducing sugars. • The fermenting bacteria SSC0ST can simultaneously uptake all the reducing sugars. • PHA content in biomass reached 31.15% w/w with PHA concentration of up to 3.06 g/L. [ABSTRACT FROM AUTHOR]