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Polyhydroxybutyrate (PHB) is known for wide applications, biocompatibility, and degradability; however, it cannot be commercialized due to conventional recovery using solvents. The present study employed mechanical cell-disruption methods, such as Pestle and mortar, sonication, and glass bead vortexing, for solvent-free extraction of PHA from Bacillus sp. Different time intervals were set for grinding (5, 10, 15 min), sonicating (1, 3 and 5 min), and vortexing (2, 5 and 8 g glass beads with 5, 10 and 15 min each) hence studying their effect on cell lysis to release PHA. Tris buffer containing phenylmethyl sulfonyl fluoride (PMSF) (20 mM Tris–HCl, pH 8.0, 1 mM PMSF) was employed as a lysis buffer to study its action over Bacillus cells. Its presence was checked with the above methods in cell lysis. Sonicating cells for 5 min in the presence of lysis buffer achieved a maximum PHA yield of 45%. Cell lysis using lysis buffer yielded 35% PHA when vortexing with 5 g glass beads for 15 min. Grinding cells for 15 min showed a maximum yield of 34% but lacked a lysis buffer. The overall results indicated that the action of lysis buffer and physical extraction methods improved PHA yield by %. Therefore, the study sought to evaluate the feasibility of applying laboratory methods for cell disruption. These methods can showcase possible opportunities in large-scale applications. The polymer yield results were compared with standard sodium hypochlorite extraction. Confirmation of obtained polymers as polyhydroxy butyrate (PHB) was made through FTIR and 1HNMR characterization. [ABSTRACT FROM AUTHOR]

The microbial biotransformation using low-cost feedstock to produce biopolymers (degradable), an alternative to petrochemical-based synthesis plastics (non-degradable), can be a beneficial approach towards sustainable development. In this study, the dairy industry processes waste (whey) is used in polyhydroxyalkanoate (PHA) copolymer production. Initial screening suggested that Ralstonia eutropha produced higher PHA as compared to Bacillus megaterium. A central composite rotatable design-based optimization using two process variables (amino acid and tween-80) concentration remarkably influenced PHA co-polymer production under physiological conditions of pH (7), temperature (37 °C), and agitation rate of 150 rpm. High polyhydroxybutyrate (PHB) mass fraction yield of 69.3% was observed as compared to predicted yield of 62.8% from deproteinized whey as feed. The combination of tryptophan (50 mg L−1) and tween-80 (3 mL−1) enhanced R. eutropha mass gain to 6.80 g L−1 with PHB contents of 4.71 g L−1. Further, characterization of PHA and its copolymers was done by ESI–MS, FTIR, and TEM. On upscaling up to 3.0 L, the PHA contents and yields were noted as quite similar by R. eutropha. This study demonstrates that dairy waste processing waste can be potentially utilized as inexpensive feed for producing high content of biopolymers to develop a sustainable system of waste management. [ABSTRACT FROM AUTHOR]

Poly-β-hydroxybutyrate (PHB) is a potential source of biodegradable plastics that are environmentally friendly due to their complete degradation to water and carbon dioxide. This study aimed to investigate PHB production in the cyanobacterium Synechocystis sp. PCC6714 MT_a24 in an outdoor bioreactor using urban wastewater as a sole nutrient source. The culture was grown in a thin-layer raceway pond with a working volume of 100 L, reaching a biomass density of up to 3.5 g L−1 of cell dry weight (CDW). The maximum PHB content was found under nutrient-limiting conditions in the late stationary phase, reaching 23.7 ± 2.2% PHB per CDW. These data are one of the highest reported for photosynthetic production of PHB by cyanobacteria, moreover using urban wastewater in pilot-scale cultivation which multiplies the potential of sustainable cultivation approaches. Contamination by grazers (Poterioochromonas malhamensis) was managed by culturing Synechocystis in a highly alkaline environment (pH about 10.5) which did not significantly affect the culture growth. Furthermore, the strain MT_a24 showed significant wastewater nutrient remediation removing about 72% of nitrogen and 67% of phosphorus. These trials demonstrate that the photosynthetic production of PHB by Synechocystis sp. PCC6714 MT_a24 in the outdoor thin-layer bioreactor using urban wastewater and ambient carbon dioxide. It shows a promising approach for the cost-effective and sustainable production of biodegradable carbon-negative plastics. Key points: • High PHB production by cyanobacteria in outdoor raceway pond • Urban wastewater used as a sole source of nutrients for phototrophic growth • Potential for cost-effective and sustainable production of biodegradable plastics [ABSTRACT FROM AUTHOR]

Poly-β-hydroxybutyrate (PHB) is a potential source of biodegradable plastics that are environmentally friendly due to their complete degradation to water and carbon dioxide. This study aimed to investigate PHB production in the cyanobacterium Synechocystis sp. PCC6714 MT_a24 in an outdoor bioreactor using urban wastewater as a sole nutrient source. The culture was grown in a thin-layer raceway pond with a working volume of 100 L, reaching a biomass density of up to 3.5 g L−1 of cell dry weight (CDW). The maximum PHB content was found under nutrient-limiting conditions in the late stationary phase, reaching 23.7 ± 2.2% PHB per CDW. These data are one of the highest reported for photosynthetic production of PHB by cyanobacteria, moreover using urban wastewater in pilot-scale cultivation which multiplies the potential of sustainable cultivation approaches. Contamination by grazers (Poterioochromonas malhamensis) was managed by culturing Synechocystis in a highly alkaline environment (pH about 10.5) which did not significantly affect the culture growth. Furthermore, the strain MT_a24 showed significant wastewater nutrient remediation removing about 72% of nitrogen and 67% of phosphorus. These trials demonstrate that the photosynthetic production of PHB by Synechocystis sp. PCC6714 MT_a24 in the outdoor thin-layer bioreactor using urban wastewater and ambient carbon dioxide. It shows a promising approach for the cost-effective and sustainable production of biodegradable carbon-negative plastics. Key points: • High PHB production by cyanobacteria in outdoor raceway pond • Urban wastewater used as a sole source of nutrients for phototrophic growth • Potential for cost-effective and sustainable production of biodegradable plastics [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB), a sustainable biodegradable polymer with various industrial and medical applications, produced by microorganisms is a good replacement of conventional plastics, a major environmental contaminant. The aim of this study is to isolate and evaluate the PHB producing ability of the microorganisms isolated from various soil sources. By employing different staining methods such as Sudan black B, Nile red and Nile blue A, the primary screening of PHB producers was performed. Among the 104 soil isolates, four strains (SNA1, SNA2, SNA3 and SNA4) exhibited positive results for all the staining tests. On further studies, among these the strain SNA2 produced highest level of PHB (64%) from its whole cell dry weight, while glucose (20 g/L) and urea (2 g/L) were used as the carbon and nitrogen sources respectively at pH 7, 30 °C after 48 h of incubation. The Fourier transform infrared spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance (1H NMR) results confirmed that the polymer produced was PHB. The 16S rRNA sequencing revealed results that the strain SNA2 was Klebsiella pneumonia. The production ability of the novel Klebsiella pneumonia SNA2 was further enhanced by optimizing various process parameters such as carbon and nitrogen sources, pH, temperature and incubation period. The process optimization resulted in enhanced PHB synthesis (up to 75%) with Xylose as carbon source and urea as the nitrogen source with pH 7.5 at 35 °C after 36 h. In addition, an attempt to produce a biofilm from the extracted polymer was also successful. Thus, the novel bacterial isolate Klebsiella pneumonia SNA2 was proved to be a challenging host for the synthesis of PHB and the scale up studies are under progress. Whole genome sequencing, identification of pathway genes and metabolic engineering strategies were believed to enhance the PHB synthesis further to the industrial scale. [ABSTRACT FROM AUTHOR]

The increase in environmental consciousness has promoted the use of renewable resources. A tremendous spike has been observed in the use of products that decompose into environment-friendly constituents, which leads to the protection of the environment. Such environment-centric thinking has reduced the volume of solid waste generated by consumers every year, together with reuse and recycling. However, the environmentally friendly initiatives and regulations face a setback when the cost is high. Often the quality of such products is compromised in comparison with synthetically derived products for consumer usage. Plastic is a ubiquitous pollutant with potentially harmful effects on living beings. The increasing population and a steady increase in petrochemical plastics' demand hamper global plastic waste management. The use of bioplastics has helped us to overcome these issues. Poly(hydroxybutyrate) (PHB) is commonly known, first synthesized bioplastic, which has strong potential in replacing conventional plastics. This review focuses on the PHB biopolymer's significant properties over plastic, its application in different fields, i.e., medical science, agriculture, construction, packaging, energy, etc. It also covers PHB biosynthesis using different waste products as a substrate to minimize the production process cost, degradation, and different analytical methods to characterize the PHB. Along with these, we have also discussed about the other polysaccharide based biodegradable polymers. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrates (PHBs) are macromolecules synthesized by bacteria. PHBs are the most promising type of bioplastic; they are nontoxic, biodegradable and biocompatible and have properties similar to those of conventional plastics. In the present study, an attempt was made to screen of different bacterial isolates accumulating PHB from soil samples collected from Istanbul, Turkey. A total of 86 different bacterial isolates were isolated from soil samples and a total of 32 isolates were suggested to be PHB producer when stained with Sudan Black B, a preliminary screening agent for lipophilic compounds. 13 bacterial isolates were selected as PHB producing isolates by using the Nile blue A dying technique. 16S rRNA gene sequences analysis showed that PHB producing 13 isolates belonged to Pseudomonas, Arthrobacter and Bacillus genera. The PHB from the isolates was extracted using the dispersion method of the hypochlorite and chloroform method. The highest PHB production and percentage productivity were obtained from Pseudomonas plecoglossicida M9 (0.94 PHB g/L; 78.8% PHB) and Pseudomonas baetica Y6 (0.81 PHB g/L; 74.3% PHB) respectively. [ABSTRACT FROM AUTHOR]

The increasing use of synthetic polymers and their disposal has raised concern due to their adverse effects on the environment. Thus, other sustainable alternatives to synthetic plastics have been sought, such as polyhydroxyalkanoates (PHAs), which are promising microbial polyesters, mainly due to their compostable nature, biocompatibility, thermostability, and resilience, making this biopolymer acceptable in several applications in the global market. The large-scale production of PHAs by microorganisms is still limited by the high cost of production compared to conventional plastics. This review reports some strategies mentioned in the literature aimed at production and recovery, paving the way for the bio-based economy. For this, some aspects of PHAs are addressed, such as synthesis, production systems, process control using by-products from industries, and advances and challenges in the downstream. The bioplastics properties made them a prime candidate for food, pharmaceutical, and chemical industrial applications. With this paper, it is possible to see that biodegradable polymers are promising materials, mainly for reducing the pollution produced by polymers derived from petroleum. [ABSTRACT FROM AUTHOR]

The increasing use of synthetic polymers and their disposal has raised concern due to their adverse effects on the environment. Thus, other sustainable alternatives to synthetic plastics have been sought, such as polyhydroxyalkanoates (PHAs), which are promising microbial polyesters, mainly due to their compostable nature, biocompatibility, thermostability, and resilience, making this biopolymer acceptable in several applications in the global market. The large-scale production of PHAs by microorganisms is still limited by the high cost of production compared to conventional plastics. This review reports some strategies mentioned in the literature aimed at production and recovery, paving the way for the bio-based economy. For this, some aspects of PHAs are addressed, such as synthesis, production systems, process control using by-products from industries, and advances and challenges in the downstream. The bioplastics properties made them a prime candidate for food, pharmaceutical, and chemical industrial applications. With this paper, it is possible to see that biodegradable polymers are promising materials, mainly for reducing the pollution produced by polymers derived from petroleum. [ABSTRACT FROM AUTHOR]

Microorganisms have been contemplated as a promising source for the inexhaustible synthesis of many novel materials utilizing renewable sources. Among many of such products, polyhydroxyalkanoate (PHA) remains as an essential biodegradable polymer with functions similar to conventional plastics. Bacillus endophyticus is capable of accumulating biopolymer PHA in nutrient limiting conditions with excess of carbon source. Screening and optimizing the parameters for increased PHA production was done statistically. The optimized medium gave a maximum yield of 46.57% which was in well agreement with the given predicted value provided by response surface methodology model yield of 47.02%. Optimal media conditions when extrapolated in bioreactor gave an even higher production percentage of 49.9. This is the first report highlighting 49% of polyhydroxybutyrate statistically using sucrose as a source. The main highlight of the study was the use of wild type strain for producing high quality PHA using simple carbon source which can be a starting platform for using this strain for large scale PHA production industrially. FTIR and 1HNMR analysis confirmed the polymer produced. [ABSTRACT FROM AUTHOR]

Waste cooking oil (WCO) is of increasing interest as an inexpensive feedstock to produce biodegradable plastic, poly(3-hydroxybutyrate) [P(3HB)]. In the present study, palm oil-based WCO (PO-WCO) was obtained from nine different locations. Palm oil-based fresh cooking oil (PO-FCO) and PO-WCO were characterised via proximate and physicochemical analysis, prior to being used as carbon sources for the biosynthesis of P(3HB) using Cupriavidus necator H16. It was shown that the free fatty acid, peroxide value, and saturated compounds in all batches of PO-WCO were higher compared to those in the PO-FCO. The cells produced 60-80 wt% P(3HB) with dry cell weight of 14-17 g/L. The weight average molecular weight (Mw) was found to be 1.8×106 Da with a polydispersity (Mw/Mn) of 2.7 when PO-WCO was used as the carbon source. The PO-WCO was found to be suitable to be used as a sustainable carbon source for cell growth and P(3HB) biosynthesis. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are biodegradable bioplastics that are synthesized by diverse bacteria. In this study, the synthesis of PHAs by the model aromatic-degrading strain Burkholderia xenovorans LB400 was analyzed. Twelve pha genes including three copies of phaC and five copies of the phasin-coding phaP genes are distributed among the three LB400 replicons. The phaC1ABR gene cluster that encodes the enzymes of the PHA anabolic pathway is located at chromosome 1 of strain LB400. During the growth of strain LB400 on glucose under nitrogen limitation, the expression of the phaC1, phaA, phaP1, phaR, and phaZ genes was induced. Under nitrogen limitation, PHA accumulation in LB400 cells was observed by fluorescence microscopy after Nile Red staining. GC-MS analyses revealed that the PHA accumulated under nitrogen limitation was poly(3- hydroxybutyrate) (PHB). LB400 cells grown on glucose as the sole carbon source under nitrogen limitation accumulated 40 ± 0.96% PHB of the cell dry weight, whereas no PHA was observed in cells grown in control medium. The functionality of the phaC1 gene from strain LB400 was further studied using heterologous expression in a Pseudomonas putida KT40C1ZC2 mutant strain derived from P. putida KT2440 that is unable to synthesize PHAs. Interestingly, KT40C1ZC2[pVNC1] cells that express the phaC1 gene from strain LB400 were able to synthesize PHB (33.5% dry weight). This study indicates that B. xenovorans LB400 possesses a functional PHA synthetic pathway that is encoded by the pha genes and is capable of synthesizing PHB. [ABSTRACT FROM AUTHOR]

We isolated Burkholderia sp. AIU M5M02, which accumulates poly(3-hydroxybutyrate) [P(3HB)] homopolymer in a nitrogen-limiting mineral salt medium containing mannitol as a sole carbon source, from a marine environment. When the isolated strain was cultured in a nitrogen-limiting mineral salt medium (pH 5.0) containing 10% (v/v) mannitol as a sole carbon source for 4 days, P(3HB) content and P(3HB) productivity reached 40 weight percent and 1.5 g/l, respectively. Thus, we demonstrated that Burkholderia sp. AIU M5M02 can be utilized for P(3HB) production from mannitol, which is a major sugar in seaweed. Furthermore, the isolate utilized not only mannitol but also gluconic acid, glycerol, starch, and sugars such as fructose, glucose, maltose, sucrose, and xylose to produce P(3HB). Based on these results, we expect to be able to apply Burkholderia sp. AIU M5M02 to the production of P(3HB) from other raw materials with low environmental loads. [ABSTRACT FROM AUTHOR]

A chemosynthetic aliphatic polyester, poly(ethylene succinate) (PESu), was degraded by a poly(3-hydroxybutyrate) (P(3HB)) depolymerase in vitro. While P(3HB) exhibited good biodegradability in all environments, PESu hardly underwent biodegradation in a marine environment. To understand the difference in environmental degradability between PESu and P(3HB), we investigated the distribution of P(3HB)- and PESu-degrading microbes in various environments. PESu-degrading microbes were never detected in marine environments. PESu-degrading bacteria isolated from various environments in this study belonged to the phyla Firmicutes and Proteobacteria. Most PESu-degrading bacterial isolates could not degrade P(3HB), suggesting that PESu was not degraded by P(3HB) depolymerase in actual environments. In addition, all bacterial isolates that were screened for P(3HB) degrading activity from various environments in this study did not degrade PESu, suggesting that PESu does not induce P(3HB) depolymerase in their bacteria and P(3HB)-degrading bacteria are not involved in biodegradation of PESu in actual environments. Taken together, these results could be related with the low biodegradability of PESu in marine environments. [ABSTRACT FROM AUTHOR]

Poly-3- d-hydroxybutyrate (or PHB) is a polyester which can be used in the production of biodegradable plastics from renewable resources. It is naturally produced by several bacteria as a response to nutrient starvation in the excess of a carbon source. The yeast Saccharomyces cerevisiae could be an alternative production host as it offers good inhibitor tolerance towards weak acids and phenolic compounds and does not depolymerize the produced PHB. As nitrogen limitation is known to boost the accumulation of PHB in bacteria, the present study aimed at investigating the effect of nitrogen availability on PHB accumulation in two recombinant S. cerevisiae strains harboring different xylose consuming and PHB producing pathways: TMB4443 expressing an NADPH-dependent acetoacetyl-CoA reductase and a wild-type S. stipitis XR with preferential use of NADPH and TMB4425 which expresses an NADH-dependent acetoacetyl-CoA reductase and a mutated XR with a balanced affinity for NADPH/NADH. TMB4443 accumulated most PHB under aerobic conditions and with glucose as sole carbon source, whereas the highest PHB concentrations were obtained with TMB4425 under anaerobic conditions and xylose as carbon source. In both cases, the highest PHB contents were obtained with high availability of nitrogen. The major impact of nitrogen availability was observed in TMB4425, where a 2.7-fold increase in PHB content was obtained. In contrast to what was observed in natural PHB-producing bacteria, nitrogen deficiency did not improve PHB accumulation in S. cerevisiae. Instead the excess available carbon from xylose was shunted into glycogen, indicating a significant gluconeogenic activity on xylose. [ABSTRACT FROM AUTHOR]

The possibility of preparing a biomaterial based on a mixture of biocompatible and biodegradable polymers, polyhydroxybutyrate and polycaprolactone, was studied. Samples for laboratory tests were prepared by forming films from an emulsion of solutions of biologically active compounds in a solution of the polymers in an organic solvent. Trypsin was used as the proteolytic component. Films containing chlorhexidine digluconate, pefloxacin, and furazolidone were studied in order to find the optimum antimicrobial component. The optimum composition of the molding mixture for preparing films with the optimal properties, i.e., trypsin activity 52.5% of the initial value, vapor permeability 4.5 mg/cm2, furazolidone desorption rate 25% C/ C, and properties 90% stable after storing in normal saline, was determined. [ABSTRACT FROM AUTHOR]

This study aimed to enhance production of polyhydroxybutyrate P(3HB) by a newly engineered strain of Cupriavidus necator NSDG-GG by applying response surface methodology (RSM). From initial experiment of one-factor-at-a-time (OFAT), glucose and urea were found to be the most significant substrates as carbon and nitrogen sources, respectively, for the production of P(3HB). OFAT experiment results showed that the maximum biomass, P(3HB) content, and P(3HB) concentration of 8.95 g/L, 76 wt%, and 6.80 g/L were achieved at 25 g/L glucose and 0.54 g/L urea with an agitation rate of 200 rpm at 30 °C after 48 h. In this study, RSM was applied to optimize the three key variables (glucose concentration, urea concentration, and agitation speed) at a time to obtain optimal conditions in a multivariable system. Fermentation experiments were conducted in shaking flask by cultivation of C. necator NSDG-GG using various glucose concentrations (10-50 g/L), urea concentrations (0.27-0.73 g/L), and agitation speeds (150-250 rpm). The interaction between the variables studied was analyzed by ANOVA analysis. The RSM results indicated that the optimum cultivation conditions were 37.70 g/L glucose, 0.73 g/L urea, and 200 rpm agitation speed. The validation experiments under optimum conditions produced the highest biomass of 12.84 g/L, P(3HB) content of 92.16 wt%, and P(3HB) concentration of 11.83 g/L. RSM was found to be an efficient method in enhancing the production of biomass, P(3HB) content, and P(3HB) concentration by 43, 21, and 74%, respectively. [ABSTRACT FROM AUTHOR]

The microbial communities responsible for the degradation of poly(lactic acid)/poly(3-hydroxybutyrate) (PLA/PHB) blend foils were investigated in 1 year long laboratory soil burial experiments. Different PLA/PHB foils were tested: (a) PLA/PHB original transparent foil, (b) PLA/PHB carbon black filled foil and (c) PLA/PHB black foil previously exposed for 90 days to sun light. The microbiome diversity of these three types of foil was compared with that identified from soil/perlite sample at the beginning of experiment and that developed on a cellulose mat. Culture-dependent and culture-independent (DGGE-cloning) approaches together with PLA, PHB and PLA/PHB degradation plate assays were employed. The cultivation strategy combined with degradation tests permitted the isolation and evaluation of several PLA/PHB blend degrading microorganisms such as members of the genera Bacillus, Paenibacillus, Streptomyces, Rhodococcus, Saccharothrix, Arthrobacter, Aureobasidium, Mortierella, Absidia, Actinomucor, Bjerkandera, Fusarium, Trichoderma and Penicillium. The DGGE-cloning investigation increased the information about the microbial communities occurring during bioplastic degradation detecting several bacterial and fungal taxa and some of them (members of the orders Anaerolineales, Selenomonadales, Thelephorales and of the genera Pseudogymnoascus and Pseudeurotium) were revealed here for the first time. This survey showed the microbiome colonizing PLA/PHB blend foils and permitted the isolation of several microorganisms able to degrade the tested polymeric blends. [ABSTRACT FROM AUTHOR]