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Magnetite nanoparticles (MNP)-caused enhancements for H2 yield (HY) are usually justified based on oxidation-reduction potential (ORP), iron ions (Fe+2/+3) concentration, and enzymatic activity, that is pH-dependent. However, the questions “If pH, ORP, and Fe+2/+3 impacts are excluded, will MNP-caused HY enhancement be still present? and how electrical energy input (EEI) affects HY?” are still unanswered. Herein, control, MNP-supplemented, EEI-applied, FeCl3-, and Na2S-supplemented batches, referred as G1, G2, G3, G5, and G6, respectively were conducted, under fixed pH (6.0 ± 0.1). G5 and G6 targeted quantifying sole impact of Fe+2/+3, and ORP, respectively on HY. G1, G2, G3, G5, and G6 achieved HY values of 1.10 ± 0.05, 1.66 ± 0.07, 1.38 ± 0.06, 1.18 ± 0.04, and 1.16 ± 0.05 mol H2/molhexose, respectively. Neither Fe+2/+3 release nor ORP reduction significantly affected HY. Further, Clostridium amylolyticum dominance was almost similar among G2, and G3. Metabolites flux analysis and functional genes’ prediction highlighted that G2 achieved highest hydrogenase expression and lowest homoacetogenic H2 consumption.

In the current global scenario, the world is under a serious dilemma due to the increasing human population, industrialization, and urbanization. The ever-increasing need for fuels and increasing nutritional problems have made a serious concern on the demand for nutrients and renewable and eco-friendly fuel sources. Currently, the use of fossil fuels is creating ecological and economic problems. Microalgae have been considered as a promising candidate for high-value metabolites and alternative renewable energy sources. Microalgae offer several advantages such as rapid growth rate, efficient land utilization, carbon dioxide sequestration, ability to cultivate in wastewater, and most importantly, they do not participate in the food crop versus energy crop dilemma or debate. An efficient microalgal biorefinery system for the production of lipids and subsequent byproduct for nutraceutical applications could well satisfy the need. But, the current microalgal cultivation systems for the production of lipids and nutraceuticals do not offer techno-economic feasibility together with energy and environmental sustainability. This review article has its main focus on the production of lipids and nutraceuticals from microalgae, covering the current strategies used for lipid production and the major high-value metabolites from microalgae and their nutraceutical importance. This review also provides insights on the future strategies for enhanced microalgal lipid production and subsequent utilization of microalgal biomass. Graphical abstract

The effect of cost-effective combined pretreatment on rice straw for lignin solubilization and the recovery of biomethane.

Hydrogen can be produced in an environmentally friendly manner through biological processes using a variety of organic waste and biomass as feedstock. However, the complexity of biological processes limits their predictability and reliability, which hinders the scale-up and dissemination. This article reviews contemporary research and perspectives on the application of machine learning in biohydrogen production technology. Several machine learning algorithems have recently been implemented for modeling the nonlinear and complex relationships among operational and performance parameters in biohydrogen production as well as predicting the process performance and microbial population dynamics. Reinforced machine learning methods exhibited precise state prediction and retrieved the underlying kinetics effectively. Machine-learning based prediction was also improved by using microbial sequencing data as input parameters. Further research on machine learning could be instrumental in designing a process control tool to maintain reliable hydrogen production performance and identify connection between the process performance and the microbial population.

Microalgae enablefixation of CO

Biohydrogen (bio-H

Lactic acid bacteria (LAB) are non-mobile, gram-positive, non-spore-forming, micro-aerophilic microorganisms widely explored as starter cultures food industry to enhance the gustatory, nutritional value, imparts appetizing flavour, texture to milk, vegetative, meat foods and prolongs their shelf life. This vast review emphasis various LABs widely explored in the food industry. Herein, we have summarized the classification of LAB strains, their metabolic pathways for biosynthesis of lactic acid, ethanol, acetic acid and demonstrated their application in various food industries for making fermented milk (yoghurt), cheese, beverages, bread, and animal foods. The wide spectrum of LAB-based probiotics, bacteriocins, exopolysaccharides, bio preservative and their relevant benefits towards human health has also been discussed. Moreover, LAB bacteriocins and probiotics in food application may limit the growth of pathogenic, while boosting health immunity. Microbial exopolysaccharides have interesting characteristics for the fermented food industry as new functional foods. Later on, we have discussed the various advancement in metabolic engineering, synthetic biology tools, which have gained considerable interest to elucidate the biosynthetic pathway for tailoring cellular metabolism for high activity.

Bioelectrochemical systems (BESs) are a new and emerging technology in the field of fermentation technology. Electrical energy was provided externally to the microbial electrolysis cells (MECs) to generate hydrogen or value-added chemicals, including caustic, formic acid, acetic acid, and peroxide. Also, BES was designed to recover nutrients, metals or remove recalcitrant compounds. The variety of naturally existing microorganisms and enzymes act as a biocatalyst to induce potential differences amid the electrodes. BESs can be performed with non-catalyzed electrodes (both anode and cathode) under favorable circumstances, unlike conventional fuel cells. In recent years, value-added chemical producing microbial electrosynthesis (MES) technology has intensely broadened the prospect for BES. An additional strategy includes the introduction of innovative technologies that help with the manufacturing of alternative materials for electrode preparation, ion-exchange membranes, and pioneering designs. Because of this, BES is emerging as a promising technology. This article deliberates recent signs of progress in BESs so far, focusing on their diverse applications beyond electricity generation and resulting performance.

Leaching of cobalt and nickel into diverse water streams has become an environmental hazard and is continuously impacting human health through the food chain. Solvent extraction is the most widely accepted for separating these metals, but traditional extractants employed in conjunction with molecular diluents often lack selectivity and caused major environmental hurdles. Therefore, the development of cost-effective, environmentally friendly technologies for recovering these heavy metals has been strongly encouraged in recent years. Herein, two halogens free, low viscous, biocompatible fatty acid-based hydrophobic ionic liquids (ILs), i.e., methytrioctylammonium oleate, methytrioctylammonium linoleate were synthesized, analytically characterized and employed for recovery of cobalt, Co(II) and nickel, Ni(II) from their aqueous solutions. Extraction behaviour of Co(II) and Ni(II) was further evaluated by varying equilibrium time, ILs molar concentration, metal loading, and temperature. Thermodynamic parameters such as enthalpy change and Gibbs free energy change were also studied during extraction process. Slope analysis suggested that the extraction mechanism was an exothermic process that followed ion-transfer from the aqueous phase to the organic phase. Results showed that both fatty acid based-ILs were found to be capable of extracting99% of Co(II) and Ni(II) from aqueous solutions at 298 K, in 15 min of shaking time using a 1:1 (org: aq.) ratio at low concentrations of 2.5-10 g L

This study investigated microalgal CO2 fixation at the CO2 concentration ranging from 5 to 40% and the CO2 loading rate of 14.4 to 57.6 L/L-d. Chlorella sp. (AG10133) was selected as the optimal strain for CO2 fixation among examined algal strains. The microalgal CO2 fixation was highly dependent on the CO2 loading rate as well as CO2 concentration. In batch culture, the highest CO2 fixation rate of 1.785 g/L-d was obtained at the CO2 concentration and the CO2 loading rate of 15% and 43.2 L/L-d, respectively. The high CO2 fixation performance was maintained at CO2 40% with the same CO2 loading rate. On the other hand, CO2 loading rate over 43.2 L/L-d at CO2 15% deteriorated CO2 fixation along with the decrease of microalgal growth. In continuous culture, the CO2 fixation rate of 2.25 g/L-d was achieved at the pseudo-steady state. The microalgal CO2 fixation would be suitable for high-strength CO2 gas stream such as biogas by providing proper CO2 loading rate.

Algal biomass has significant advantages over terrestrial plants in terms of CO2 sequestration, biomass productivity, wastewater treatment along with multiple biobased products synthesis. Metabolic versatility and high carbohydrate content of microalgal biomass act as a potential alternative feedstock to fossil resources and contribute towards the biobased economy growth. Effective biomass utilization would play a key role to establish sustainable bioprocess development and technology translation to the industrial community. In this framework, the present review discusses the renewable resource potential of algal biomass and its complete utilization for multiple biobased products synthesis in a closed-loop biorefinery approach. Various methods are discussed to obtain high biomass growth and pretreatments to obtain the maximum sugars solubilization. Further, combined bioprocesses were discussed for the production of biohydrogen, biomethane, bioethanol, short-chain fatty acids (SCFA), medium-chain fatty acids (MCFA), and biopolymers in a closed-loop approach.

In this work, the potential of utilizing a polyetherimide (PEI) hollow-fiber membrane to separate synthetic biohydrogen mixture (H2/CO2) was studied. From the gas separation experiments, where the effects of feed to permeate pressure ratio (Pfeed/Ppermeate) and stage-cut as key factors were evaluated, it was found that the PEI membrane had the capacity to purify either H2 or CO2. It turned out that different separation settings should be chosen in accordance with the actual technological purpose, defined either as the enrichment of H2 or CO2. The highest H2 concentration (66.4 vol%) in the permeate was achieved at Pfeed/Ppermeate of 4.62 and stage-cut of 0.47, while the peak CO2 concentration (79.2 vol%) in the retentate was obtained by applying Pfeed/Ppermeate of 4.55 and stage-cut of 0.65. The assessment and discussion of results indicated the possible utilization of the CO2-rich fraction (produced by the PEI membrane) for the biological sequestration using microalgae. To our knowledge, PEI membranes have not yet been tested in such a concept and thus, the results and experiences can mean a new contribution to the literature.

Food waste (FW) can be utilized as a raw material to produce energy such as hydrogen via fermentation, which is a more attractive and environmentally friendly approach compared to incineration and land-filling. Food waste must be pretreated before being used in various biological processes. The choice of the pretreatment method usually depends on the composition of the food waste. Therefore, various pretreatment methods generally employed to treat FW, including physical, physiochemical, chemical and biological pretreatments, are summarized in this review. The different pretreatment methods are compared in terms of their efficiency and biohydrogen yield. Additionally, the energy efficiencies of the various pretreatment methods are compared, thereby leading to the selection of the most efficient pretreatment method.

A continuous stirred tank reactor (CSTR) was operated for more than 120 days with fixed hydraulic retention time of 6 h at mesophilic temperature along with a periodic recovery phase towards hydrogen production and stimulated by the existence of 5-hydroxy methyl furfural concentration (5-HMF). Interestingly, CSTR mixed with a small amount of 5-HMF, range of 0.3–0.6 g/L showed at least 50% higher hydrogen production rate than control without 5-HMF. However, when 5-HMF concentration was higher than 0.6 g/L, the performance was significantly inhibited. The bacterial community shifted by 5-HMF from Clostridium-dominated to Lactobacillus-dominated population. Regardless of the remain 5-HMF concentration in CSTR, the microbial community and hydrogen producing performance were restored by stop mixing the 5-HMF from the feedstock. The high-rate hydrogen production of 20.0 ± 1.8 L H2/L/d was achieved in the presence of 5-HMF using the threshold information and recovery strategy.

The effects of bamboo biochar (BB) variables on gaseous emissions, maturity and microbial dynamics during composting of sheep manure were investigated. The experiments were conducted with six different ratio of BB (0%, 2%, 4%, 6%, 8% and 10% dry weight based) and 0% is compiled as control. The results showed that 10%BB provided rapid mineralization and less time duration of compost maturity. 10% BB has the excellent impact on greenhouse gas (GHG) emission reduction and nutrients conservation (nitrogen and carbon losses were 13.40 g/kg and 124.42 g/kg) as compared to other treatments. Control was significantly different from other treatments in terms of GHG emission and nitrogen loss and had the lowest germination index after 42 days composting. BB addition were the main factors influencing GHG emission and improve the bacterial abundance. There is a significant correlation among the analyzed physicochemical factors, gaseous emission and bacterial phylum is used 8–10% BB for SM composting. Higher percentages of BB not only reduced CH4 and N2O emissions but also showed significant influence on CO2 and NH3 losses as well as improve the end product quality.

This study reviewed the recent updates on the pretreatment methods employed towards the enhancement of hydrogen production. Low hydrogen yield was considered to be a current obstacle for hydrogen utility on the industrial scale. On pretreating, the wastewater, the structure of the macromolecule gets dissipated and destroyed which reduces the polymerization potency. It favors the availability of monomers for the fermentation process. Various pretreatment methods with operating conditions and parameters were documented along with their pros and cons. Mainly, the pretreatment methods adopted for reducing the toxicity levels of wastewater to enhance biohydrogen production are dealt with in detail. Pretreatment methods have shown a positive impact on most of the cases studied. It acts on various components of wastewater and makes it amenable for the hydrogen-producing microbiome. Energy balance methodologies have also been provided towards the selection of a cost-effective and sustainable approach. Perspectives and recommendations on pretreatment systems were directed towards the development of a successful hydrogen economy. Overall documentation details the significance of pretreatment in the fermentation process for higher hydrogen yield.

Organic waste has increased as the global population and economy have grown exponentially. Food waste (FW) is posing a severe environmental issue because of mismanaged disposal techniques, which frequently result in the squandering of carbohydrate-rich feedstocks. In an advanced valorization strategy, organic material in FW can be used as a viable carbon source for microbial digestion and hence for the generation of value-added compounds. In comparison to traditional feedstocks, a modest pretreatment of the FW stream utilizing chemical, biochemical, or thermochemical techniques can extract bulk of sugars for microbial digestion. Pretreatment produces a large number of toxins and inhibitors that affect bacterial fuel and chemical conversion processes. Thus, the current review scrutinizes the FW structure, pretreatment methods (e.g., physical, chemical, physicochemical, and biological), and various strategies for detoxification before microbial fermentation into renewable chemical production. Technological and commercial challenges and future perspectives for FW integrated biorefineries have also been outlined.

Wastewater is one of the most common by-products of almost every industrial process. Treatment of wastewater alone, before disposal, necessitates an excess of energy. Environmental concerns over the use of fossil fuels as a source of energy have prompted a surge in demand for alternative energy sources and the development of sophisticated procedures to extract energy from unconventional sources. Treatment of municipal and industrial wastewater alone accounts for about 3% of global electricity use while the amount of energy embedded in the waste is at least 2-4 times greater than the energy required to treat the same effluent. The microbial electrolysis cell (MEC) is one of the most efficient technologies for waste-to-product conversion that uses electrochemically active bacteria to convert organic matter into hydrogen or a variety of by-products without polluting the environment. This paper highlights existing obstacles and future potential in the integration of Microbial Electrolysis Cell with other processes like anaerobic digestion coupled system, anaerobic membrane bioreactor and thermoelectric micro converter.

Excessive generation of wastewater is a matter of concern around the globe. Wastewater treatment utilizing a microalgae-mediated process is considered an eco-friendly and sustainable method of wastewater treatment. However, low biomass productivity, costly harvesting process, and energy extensive cultivation process are the major bottleneck. The use of the microalgal-bacteria granular consortia (MBGC) process is economic and requires less energy. For efficient utilization of MBGC, knowledge of its structure, composition and interaction are important. Various microscopic, molecular and metabolomics techniques play a significant role in understating consortia structure and interaction between partners. Microalgal-bacteria granular consortia structure is affected by various cultivation parameters like pH, temperature, light intensity, salinity, and the presence of other pollutants in wastewater. In this article, a critical evaluation of recent literature was carried out to develop an understanding related to interaction behavior that can help to engineer consortia having efficient nutrient removal capacity with reduced energy consumption.

Contamination of the environment through toxic pollutants poses a key risk to the environment due to irreversible environmental damage(s). Industrialization and urbanization produced harmful elements such as petrochemicals, agrochemicals, pharmaceuticals, nanomaterials, and herbicides that are intentionally or unintentionally released into the water system, threatening biodiversity, the health of animals, and humans. Heavy metals (HMs) in water, for example, can exist in a variety of forms that are inclined by climate features like the presence of various types of organic matter, pH, water system hardness, transformation, and bioavailability. Biological treatment is an important tool for removing toxic contaminants from the ecosystem, and it has piqued the concern of investigators over the centuries. In situ bioremediation such as biosparging, bioventing, biostimulation, bioaugmentation, and phytoremediation and ex-situ bioremediation includes composting, land farming, biopiles, and bioreactors. In the last few years, scientific understanding of microbial relations with particular chemicals has aided in the protection of the environment. Despite intensive studies being carried out on the mitigation of toxic pollutants, there have been limited efforts performed to discuss the solutions to tackle the limitations and approaches for the remediation of heavy metals holistically. This paper summarizes the risk assessment of HMs on aquatic creatures, the environment, humans, and animals. The content of this paper highlights the principles and limitations of microbial remediation to address the technological challenges. The coming prospect and tasks of evaluating the impact of different treatment skills for pollutant remediation have been reviewed in detail. Moreover, genetically engineered microbes have emerged as powerful bioremediation capabilities with significant potential for expelling toxic elements. With appropriate examples, current challenging issues and boundaries related to the deployment of genetically engineered microbes as bioremediation on polluted soils are emphasized.

Lignocellulosic biomass is projected as a prospective renewable alternative to petroleum for the production of fuel and chemicals. Pretreatment is necessary to disrupt the lignocellulosic structure for extraction of cellulose. Biomass after pretreatment is segregated into cellulose rich solid fraction and black liquor (lignin and hemicelluloses) as a liquid stream. The plant polysaccharide-based industry primarily utilizes the cellulosic fraction as raw material, and carbon rich black liquor discarded as waste or burnt for energy recovery. This review highlights the recent advancements in the biological and chemical valorization of black liquor into fuels and chemicals. The recent research attempted for bioconversion of black liquor into Bioplastic, Biohydrogen, Biogas, and chemicals has been discussed. In addition, the efforts to replace the conventional energy recovery method with the advanced chemical process along with their modifications have been reviewed that will decide the sustainability of the lignocellulosic biomass-based industry.

The 3rd International Conference for Bioresource Technology for Bioenergy, Bioproducts & Environmental Sustainability (BIORESTEC) was held online from 17 to 19 May 2021. More than 120 participants from all over the world participated in this conference. The conference was studded with nine plenary lectures, ten invited lectures as well as more than 50 oral presentations along with several poster presentations. The purpose of the conference was to foster the exchange of knowledge and ideas among researchers in academia and industry as well as policymakers working on various aspects of biorefinery to discuss the progress made during the intervening three years and the latest trends in biotechnology, bioenergy, and biobased products. Biorefinery is winning over petrol refinery due to its sustainable nature and is the major driving force to a positive push to World's bioeconomy. Biorefinery enables us to obtain cascades of products by using biomass; including bioenergy, platform chemicals and various other bioproducts. Most of the talks during the conference dealt with sustainable practices for producing or synthesizing biomolecules via microorganisms. Bacteria, fungi as well algae were presented as bio machinery to convert the waste residues into value-added products including bioenergy and other biomolecules. This virtual special issue includes a selection of papers presented at the BIORESTEC conference, which contribute to environmental sustainability and give a strong message on sustainable technologies through developing bioproducts in order to overcome environmental issues.

The development of photobioreactor is important for sustainable production of renewable fuels, wastewater treatment and CO

This study investigated the ammonia toxicity and the acclimation of anaerobic microbiome in continuous anaerobic digestion of swine manure using unacclimated inoculum. When the total ammonia nitrogen concentration (TAN) reached 2.5 g N/L, the methane yield decreased from 254.1 ± 9.6 to 154.6 ± 9.9 mL/g COD. The free ammonia nitrogen concentration of the inhibited condition was 190 mg N/L. The methane yield was eventually recovered as 269.6 ± 3.6 mL/g COD with a further operation. Anaerobic toxicity assay (ATA) showed that mixed liquor from the recovered phase possessed enhanced tolerance to ammonia, not only within the exposed level in continuous operation (2.5 g NH

Microalgae biomass has been considered as one of the potential feedstocks in biofuel production. Yet, biomass harvesting poses a challenge to the overall production cost due to its low cell density. Flocculation has been marked as one of the promising processes in microalgae harvesting technology. In this study, the first screening of two anionic (A-230, and A-330E) and five cationic polymers (C-810E, C-810EL, C-810EB, C-810ELH, and C-810EMB) followed by gravity settling with the mixed microalgae concentration of 2.24 gTSS/L revealed that anionic polymers are less effective. Whereas all cationic polymers achieved above 90% harvesting efficiency. Therefore, the maximum mass recovery of 98.7% with 86.8 gTSS/L sediment content was achieved by adjusting pH to 6–0.6 mL/L (115.178 mg/gbiomass) of C-810E followed by 15-min settling. The cationic polymer addition followed by settling would enable cost-effective downstream processing of microalgal biomass.

This study aimed to mitigate the instability in the start-up and continuous performance of dark fermentative biohydrogen production using heat-treated sludge by the addition of an exogenous H