Evolution characteristics and molecular constraints of microbial communities during coal biogasification

This study investigates the production of biomethane, and variation in microbial community and coal molecular structures using gas chromatography, 16S rRNA high-throughput sequencing and Fourier transform infrared spectroscopy. Additionally, the factors influencing microbial community structure at a molecular level are discussed. The results demonstrate that bituminous coal exhibits a higher biomethane yield than anthracite coal. In bituminous coal samples, Escherichia and Proteiniphilum are the predominant bacteria at day 0, while Macellibacteroides dominates from days 5 to 35. Methanofollis is the dominated archaea during days 0 to 15, followed by Methanosarcina on day 35. In anthracite coal samples, Soehngenia is the dominant bacterial genus at day 0; however, it transitions to mainly Soehngenia and Aminobacterium within days 5-15 before evolving into Acetomicrobium on day 35. Methanocorpusculum is predominantly found in archaeal communities during days 0-15 but shifts to Methanosarcina on day 35. Alpha diversity analysis reveals that bacterial communities have higher species abundance and diversity compared to archaeal communities. Redundancy analysis indicates a significant correlation between coal molecular structure and bacterial community composition (P value < 0.05), whereas no correlation exists with archaeal community composition (P value > 0.05). The research findings provide theoretical support for revealing the biological gasification mechanisms of coal.

Ex-situ single-culture biomethanation operated in trickle-bed configuration: Microbial H2 kinetics and stoichiometry for biogas conversion into renewable natural gas

Biomethanation converts carbon dioxide (CO2) emissions into renewable natural gas (RNG) using mixed microbial cultures enriched with hydrogenotrophic archaea. This study examines the performance of a single methanogenic archaeon converting biogas with added hydrogen (H2) into methane (CH4) using a trickle-bed bioreactor with enhanced gas-liquid mass transport. The process in continuous operation followed the theoretical reaction of hydrogenotrophic methanogenesis (CO2 + 4 H2 → CH4 + 2 H2O), producing RNG with over 99 % CH4 and more than 0.9 H2 conversion efficiency. The Monod constants of H2 uptake were experimentally determined using kinetic modelling. Also, a dimensionless parameter was used to quantify the ratio between the H2 mass transfer rate and the maximum attainable H2 consumption rate. Single-culture biomethanation averts the formation of secondary metabolites and bicarbonate buffer interferences, resulting in lower demands for H2 than mixed-culture biomethanation.

A cyclic shift-temperature operation method to train microbial communities of mesophilic anaerobic digestion

Temperature is the critical factor affecting the efficiency and cost of anaerobic digestion (AD). The current work develops a shift-temperature AD (STAD) between 35 °C and 55 °C, intending to optimise microbial community and promote substrate conversion. The experimental results showed that severe inhibition of biogas production occurred when the temperature was firstly increased stepwise from 35 °C to 50 °C, whereas no inhibition was observed at the second warming cycle. When the organic load rate was increased to 6.37 g VS/L/d, the biogas yield of the STAD reached about 400 mL/g VS, nearly double that of the constant-temperature AD (CTAD). STAD promoted the proliferation of Methanosarcina (up to 57.32 %), while severely suppressed hydrogenophilic methanogens. However, when the temperature was shifted to 35 °C, most suppressed species recovered quickly and the excess propionic acid was quickly consumed. Metagenomic analysis showed that STAD also promoted gene enrichment related to pathways metabolism, membrane functions, and methyl-based methanogenesis.

Manipulating the nucleolar serine-rich protein Srp40p in Saccharomyces cerevisiae may improve isobutanol production

Isobutanol represents a promising second-generation biofuel. Saccharomyces cerevisiae can produce minor quantities of isobutanol as a byproduct. Increasing yeast tolerance to isobutanol is a crucial step toward achieving higher production levels. Previously, we discovered that expression of the srp40 gene could increase S. cerevisiae isobutanol tolerance. In this study, we explored the impact of overexpressing srp40 on isobutanol production. We used the CEN/ARS plasmid YCplac22-srp40 to overexpress srp40 in S. cerevisiae strain W303-1A. The resulting strain was named W303-1A-srp40. We subsequently performed metabolic engineering of isobutanol synthesis by overexpressing ILV2, ILV3 and ARO10 in W303-1 A-srp40. The resulting strain was named 303V2V3A10-22-srp40. Our findings revealed that, compared with the control strain, the 303V2V3A10-22-srp40 strain amplified isobutanol production by 50%. A transcriptome analysis revealed that upregulated genes associated with aminoacyl-tRNA biosynthesis or downregulated genes associated with phenylalanine, tyrosine, and tryptophan biosynthesis might yield increased isobutanol production in 303V2V3A10-22-srp40. Moreover, the decreases in the biosynthesis of amino acids and oxidative phosphorylation might play pivotal roles in the increased isobutanol tolerance of strain W303-1A-srp40. In summary, the overexpression of srp40 could increase isobutanol production and tolerance in S. cerevisiae. This study offers novel insights regarding strategies for increasing isobutanol production.

Potential of oleaginous microbes for lipid accumulation and renewable energy generation

Biocomponents (such as lipids) accumulate in oleaginous microorganisms and could be used for renewable energy production. Oleaginous microbes are characterized by their ability to accumulate high levels of lipids, which can be converted into biodiesel. The oleaginous microbes (including microalgae, bacteria, yeast, and fungi) can utilize diverse substrates. Thus, in this study, commercially viable oleaginous microorganisms are comparatively summarized for their growth conditions, substrate utilization, and applications in biotechnological processes. Lipid content is species-dependent, as are culture conditions (such as temperature, pH, nutrients, and culture time) and substrates. Lipid production can be increased by selecting suitable microorganisms and substrates, optimizing environmental conditions, and using genetic engineering techniques. In addition, the emphasis on downstream processes (including harvesting, cell disruption, lipid extraction, and transesterification) highlights their critical role in enhancing cost-effectiveness. Oleaginous microorganisms are potential candidates for lipid biosynthesis and could play a key role in meeting the energy needs of the world in the future.

Co-cultivation of microalgae and bacteria for optimal bioenergy feedstock production in wastewater by using response surface methodology

This work uses response surface methodology (RSM) to study the co-cultivation of symbiotic indigenous wastewater microalgae and bacteria under different conditions (inoculum ratio of bacteria to microalgae, CO2, light intensity, and harvest time) for optimal bioenergy feedstock production. The findings of this study demonstrate that the symbiotic microalgae-bacteria culture not only increases total microalgal biomass and lipid productivity, but also enlarges microalgal cell size and stimulates lipid accumulation. Meanwhile, inoculum ratio of bacteria to microalgae, light intensity, CO2, and harvest time significantly affect biomass and lipid productivity. CO2 concentration and harvest time have significant interactive effect on lipid productivity. The response of microalgal biomass and lipid productivity varies significantly from 2.1 × 105 to 1.9 × 107 cells/mL and 2.8 × 102 to 3.7 × 1012 Total Fluorescent Units/mL respectively. Conditions for optimum biomass and oil accumulation are 100% of inoculation ratio (bacteria/microalgae), 3.6% of CO2 (v/v), 205.8 µmol/m2/s of light intensity, and 10.6 days of harvest time. This work provides a systematic methodology with RSM to explore the benefits of symbiotic microalgae-bacteria culture, and to optimize various cultivation parameters within complex wastewater environments for practical applications of integrated wastewater-microalgae systems for cost-efficient bioenergy production.

Bioaugmentation by enriched hydrogenotrophic methanogens into trickle bed reactors for H2/CO2 conversion

Biomethanation represents a promising approach for biomethane production, with biofilm-based processes like trickle bed reactors (TBRs) being among the most efficient solutions. However, maintaining stable performance can be challenging, and both pure and mixed culture approaches have been applied to address this. In this study, inocula enriched with hydrogenotrophic methanogens were introduced to to TBRs as bioaugmentation strategy to assess their impacts on the process performance and microbial community dynamics. Metagenomic analysis revealed a metagenome-assembled genome belonging to the hydrogenotrophic genus Methanobacterium, which became dominant during enrichment and successfully colonized the TBR biofilm after bioaugmentation. The TBRs achieved a biogas production with > 96 % methane. The bioaugmented reactor consumed additional H2. This may be due to microbial species utilizing CO2 and H2 via various CO2 reduction pathways. Overall, implementing bioaugmentation in TBRs showed potential for establishing targeted species, although challenges remain in managing H2 consumption and optimizing microbial interactions.

Industrializing methanotrophs and other methylotrophic bacteria: from bioengineering to product recovery

Microbes that use the single-carbon substrates methanol and methane offer great promise to bioindustry along with substantial environmental benefits. Methanotrophs and other methylotrophs can be engineered and optimized to produce a wide range of products, from biopolymers to biofuels and beyond. While significant limitations remain, including delivery of single-carbon feedstock to bioreactors, efficient growth, and scale-up, these challenges are being addressed and notable improvements have been rapid. Development of expression chassis, use of genome-scale and regulatory models based on omics data, improvements in bioreactor design and operation, and development of green product recovery schemes are enabling the rapid development of single-carbon bioconversion in the industrial space.

Pre-treatment with Trichoderma viride: Towards a better understanding of its consequences for anaerobic digestion

Understanding and optimising biological pre-treatment strategies for enhanced bio-methane production is a central aspect in second-generation biofuel research. In this regard, the application of fungi for pre-treatment seems highly promising; however, understanding the mode of action is crucial. Here, we show how aerobic pre-treatment of crystalline cellulose with the cellulolytic Trichoderma viride affects substrate degradability during mesophilic, anaerobic digestion. It could be demonstrated that fungal pre-treatment resulted in a slightly reduced substrate mass. Nevertheless, no significant impact on the overall methane yield was found during batch fermentation. Short chain organic acids accumulation, thus, overall degradation dynamics including methane production kinetics were affected by the pre-treatment as shown by Gompertz modelling. Finally, 16S rRNA amplicon sequencing followed by ANCOM-BC resulted in up to 53 operative taxonomic units including fermentative, syntrophic and methanogenic taxa, whereby their relative abundances were significantly affected by fungal pre-treatment depending on the duration of the pre-treatment. The results demonstrated the impact of soft rot fungal pre-treatment of cellulose on subsequent anaerobic cellulose hydrolysis as well as on methanogenic activity. To the best of our knowledge, this is the first study to investigate the direct causal effects of pre-treatment with T. viride on basic but crucial anaerobic digestion parameters in a highly standardised approach.

Chromosomal integration of the pSOL1 megaplasmid of Clostridium acetobutylicum for continuous and stable advanced biofuels production

Biofuel production by Clostridium acetobutylicum is compromised by strain degeneration due to loss of its pSOL1 megaplasmid. Here we used engineering biology to stably integrate pSOL1 into the chromosome together with a synthetic isopropanol pathway. In a membrane bioreactor continuously fed with glucose mineral medium, the final strain produced advanced biofuels, n-butanol and isopropanol, at high yield (0.31 g g-1), titre (15.4 g l-1) and productivity (15.5 g l-1 h-1) without degeneration.

High-throughput screening of non-conventional yeasts for conversion of organic waste to microbial oils via carboxylate platform

Converting waste into high-value products promotes sustainability by reducing waste and creating new revenue streams. This study investigates the potential of diverse yeasts for microbial oil production by utilizing short-chain fatty acids (SCFAs) that can be produced from organic waste and focuses on identifying strains with the best SCFA utilisation, tolerance and lipid production. A collection of 1434 yeast strains was cultivated with SCFAs as the sole carbon source. Eleven strains emerged as candidates with promising growth rates and high lipid accumulation. Subsequent fermentation experiments in liquid SCFA-rich media, which focused on optimizing lipid accumulation by adjusting the carbon to nitrogen (C/N) ratio, showed an increase in lipid content at a C/N ratio of 200:1, but with a concurrent reduction in biomass. Two strains were characterized by their superior ability to produce lipids compared to the reference strain Yarrowia lipolytica CECT124: Y. lipolytica EXF-17398 and Pichia manshurica EXF-7849. Characterization of these two strains indicated that they exhibit a biotechnologically relevant balance between maximizing lipid yield and maintaining growth at high SCFA concentrations. These results emphasize the potential of using SCFAs as a sustainable feedstock for oleochemical production, offering a dual benefit of waste valorisation and microbial oil production.

A comparative assessment of microbial biodiesel and its life cycle analysis

Biodiesel is a type of sustainable, biodegradable energy made from natural sources like vegetable oils, animal fat, and from microbes. Unlike traditional diesel, it has a lower carbon footprint and produces fewer harmful emissions when burned. Biodiesel has gained popularity as a more sustainable substitute for hydrocarbon-based diesel and may be utilized in diesel engines without any modification. In this review, biodiesel from microorganisms such as algae, yeast, and fungi and advantages over another feedstock were discussed. The life cycle evaluation of biodiesel is a thorough assessment of the ecological and economic effects of biodiesel production and use, from the extraction of raw ingredients to the waste disposal process. The life cycle analysis considers the entire process, including the production of feedstocks, the production of biodiesel, and the use of biodiesel in vehicles and other applications. Life cycle analysis of biodiesel produced from microorganisms takes into consideration the environmental impact and sustainability of each step in the production process, including the impact on land use, water use, greenhouse gas emissions, and the availability of resources. In this section, biodiesel produced from microorganisms and other raw materials, its comparisons, and also steps involved in the life cycle such as the cultivation of microorganisms, harvesting of biomass, and conversion to biodiesel were discussed. The processes like extraction and purification, hydrothermal liquefaction, and their environmental impacts were examined by using various LCA software from the previously mentioned process.

The potential of Bacillus species isolated from Cinnamomum camphora for biofuel production

BACKGROUND

Increasing concerns about climate change and global petroleum supply draw attention to the urgent need for the development of alternative methods to produce fuels. Consequently, the scientific community must devise novel ways to obtain fuels that are both sustainable and eco-friendly. Bacterial alkanes have numerous potential applications in the industry sector. One significant application is biofuel production, where bacterial alkanes can serve as a sustainable eco-friendly alternative to fossil fuels. This study represents the first report on the production of alkanes by endophytic bacteria.

RESULTS

In this study, three Bacillus species, namely Bacillus atrophaeus Camph.1 (OR343176.1), Bacillus spizizenii Camph.2 (OR343177.1), and Bacillus aerophilus Camph.3 (OR343178.1), were isolated from the leaves of C. camphora. The isolates were then screened to determine their ability to produce alkanes in different culture media including nutrient broth (NB), Luria-Bertani (LB) broth, and tryptic soy broth (TSB). Depending on the bacterial isolate and the culture media used, different profiles of alkanes ranging from C8 to C31 were detected.

CONCLUSIONS

The endophytic B. atrophaeus Camph.1 (OR343176.1), B. spizizenii Camph.2 (OR343177.1), and B. aerophilus Camph.3 (OR343178.1), associated with C. camphora leaves, represent new eco-friendly approaches for biofuel production, aiming towards a sustainable future. Further research is needed to optimize the fermentation process and scale up alkane production by these bacterial isolates.

Enhancing biogas generation from lignocellulosic biomass through biological pretreatment: Exploring the role of ruminant microbes and anaerobic fungi

Biogas production from Lignocellulosic Biomass (LB) via anaerobic digestion (AD) has gained attention for its potential in self-sustainability. However, the recalcitrance of LB cell walls pose a challenge to its degradability and biogas generation. Therefore, pretreatment of LB is necessary to enhance lignin removal and increase degradability. Among the different approaches, environmentally friendly biological pretreatment ispromising as it avoids the production of inhibitors. The ruminal microbial community, including anaerobic fungi, bacteria, and protozoa, has shown an ability to effectively degrade LB through biomechanical and microbial penetration of refractory cell structures. In this review, we provide an overview of ruminant microbes dominating LB's AD, their degradation mechanism, and the bioaugmentation of the rumen. We also explore the potential cultivation of anaerobic fungi from the rumen, their enzyme potential, and their role in AD. The rumen ecosystem, comprising both bacteria and fungi, plays a crucial role in enhancing AD. This comprehensive review delves into the intricacies of ruminant microorganisms' adhesion to plant cells, elucidates degradation mechanisms, and explores integrated pretreatment approaches for the effective utilization of LB, minimizing the impact of inhibitors. The discussion underscores the considerable potential of ruminant microbes in pretreating LB, paving the way for sustainable biogas production. Optimizing fungal colonization and ligninolytic enzyme production, such as manganese peroxidase and laccase, significantly enhances the efficiency of fungal pretreatment. Integrating anaerobic fungi through bioaugmentation during mainstream processing demonstrably increases methane production. This study opens promising avenues for further research and development of these microorganisms for bioenergy production.

Appraising the phycoremediation potential of cyanobacterial strains Phormidium and Oscillatoria for nutrient removal from textile wastewater (TWW) and synchronized biodiesel production from TWW-tolerant biomass

In this study, phycoremediation of textile wastewater (TWW) by freshwater cyanobacterial strains such as sp., Oscillatoria sp. F01 and Oscillatoria sp. F02 was evaluated, and lipids were simultaneously extracted from biomass for biodiesel production. Onset of the study, Phormidium sp. and Oscillatoria sp. F01 has better growth rates, increased biomass production, high chlorophyll content, and efficient nutrient utilization in TWW compared to Oscillatoria sp. F02. Phormidium sp. showed 1.41 g/L dry weight, followed by Oscillatoria sp. F01 with 1.39 g/L and Oscillatoria sp. F02 with 1.02 g/L biomass. Both strains demonstrated their capability to elevate the pH level while reducing TDS and eliminating/reducing several nutrients such as nitrates, nitrites, phosphates, sulphates, sulphides, chlorides, calcium, sodium, and magnesium. Further, the total lipids extracted from the TWW-grown Phormidium sp., Oscillatoria sp. F01 and Oscillatoria sp. F02 was estimated to be 8.20, 13.70 and 11.20 %, respectively, on day 21, which was higher than the lipid content obtained from control cultures. Further, biodiesel produced from the lipids of all strains showed higher levels of C12:0, C16:0, C16:1, C18:1, C18:2, and C18:3 among all the fatty acids. Therefore, they can potentially offer a valuable source of lipids and diverse fatty acids for high-quality biodiesel production. This integrated system not only offers a solution for TWW treatment but also provides a feedstock for renewable fuel production simultaneously.

Metaproteomic Analysis of Biogas Plants: A Complete Workflow from Lab to Bioinformatics

Metaproteomics represents a promising and fast method to analyze the taxonomic and functional composition of biogas plant microbiomes. However, metaproteomics sample preparation and bioinformatics analysis is still challenging due to the sample complexity and contaminants. In this chapter, a tailored workflow including sampling, phenol extraction in a ball mill, amido black protein quantification, FASP digestion, LC-MS/MS measurement as well as bioinformatics and biostatistical data evaluation are here described for the metaproteomics advancements applied to biogas plant samples.

Construction of Xylose-Utilizing Cyanobacterial Chassis for Bioproduction Under Photomixotrophic Conditions

Xylose is a major component of lignocellulose and the second most abundant sugar present in nature after glucose; it, therefore, has been considered to be a promising renewable resource for the production of biofuels and chemicals. However, no natural cyanobacterial strain is known capable of utilizing xylose. Here, we take the fast-growing cyanobacteria Synechococcus elongatus UTEX 2973 as an example to develop the synthetic biology-based methodology of constructing a new xylose-utilizing cyanobacterial chassis with increased acetyl-CoA for bioproduction.

Overview of microalgae and cyanobacteria-based biostimulants produced from wastewater and CO2 streams towards sustainable agriculture: A review

For a long time, marine macroalgae (seaweeds) have been used to produce commercial biostimulants in order to ensure both productivity and quality of agricultural crops under abiotic stress. With similar biological properties, microalgae have slowly attracted the scientific community and the biostimulant industry, in particular because of their ability to be cultivated on non-arable lands with high biomass productivity all year long. Moreover, the recent strategies of culturing these photosynthetic microorganisms using wastewater and CO2 opens the possibility to produce large quantity of biomass at moderate costs while integrating local and circular economy approaches. This paper aims to provide a state of the art review on the development of microalgae and cyanobacteria based biostimulants, focusing on the different cultivation, extraction and application techniques available in the literature. Emphasis will be placed on microalgae and cyanobacteria cultivation using liquid and gaseous effluents as well as emerging green-extraction approaches, taking in consideration the actual European regulatory framework.

Nitrogen and phosphorus stress as a tool to induce lipid production in microalgae

Microalgae, capable of accumulating large amounts of lipids, are of great value for biodiesel production. The high cost of such production stimulates the search for cultivation conditions that ensure their highest productivity. Reducing the content of nitrogen and phosphorus in the culture medium is widely used to change the content and productivity of lipids in microalgae. Achieving the right balance between maximum growth and maximum lipid content and productivity is the primary goal of many experimental works to ensure cost-effective biodiesel production from microalgae. The content of nitrogen and phosphorus in nutrient media for algal cultivation after converted to nitrogen (-N) and phosphorus (-P) lies in an extensive range: from 0.007 g L- 1 to 0.417 g L- 1 and from 0.0003 g L- 1 to 0.227 g L- 1 and N:P ratio from 0.12:1 to 823.33:1. When studying nutritional stress in microalgae, no single approach is used to determine the experimental concentrations of nitrogen and phosphorus. This precludes the possibility of correct interpretation of the data and may lead to erroneous conclusions. This work results from the systematisation of information on using nitrogen and phosphorus restriction to increase the lipid productivity of microalgae of different taxonomic and ecological groups to identify future research directions. The results of 301 experiments were included in the analysis using the principal components method. The investigation considered various divisions and classes: Cyanobacteria, Rhodophyta, Dinophyta, Haptophyta, Cryptophyta, Heterokontophyta/Ochrophyta (Bacillariophyceae, Eustigmatophyceae, Xanthophyceae), Chlorophyta, and also the ratio N:P, the time of the experiment, the light intensity during cultivation. Based on the concentrations of nitrogen and phosphorus existing in various nutrient media, a general scheme for designating the supply of nutrient media for nitrogen (as NO3- or NH4+, N g L- 1) and phosphorus (as РO4-, P g L- 1) has been proposed: replete -N (˃0.4 g L- 1), moderate -N (0.4-0.2), moderate N-limitation (0.19-0.1), strong N-limitation (˂0.1), without nitrogen (0), replete -Р (˃0.2), moderate -P (0.2-0.02), moderate P-limitation (0.019-0.01), strong P-limitation (˂0.01), without phosphorus (0).

Quantification of indicator and pathogenic bacteria in manures and digestates from three agricultural biogas plants over a one-year period

Interest in the conversion of manure in biogas via anaerobic digestion (AD) is growing, but questions remain about the biosafety of digestates. For a period of one year, we monitored the impact of three mesophilic agricultural biogas plants (BPs) mainly fed with pig manure (BP1, BP3) or bovine manure (BP2) on the physicochemical parameters, the composition of the microbial community and the concentration of bacteria (E. coli, enterococci, Salmonella, Campylobacter, Listeria monocytogenes, Clostridium perfringens, Clostridium botulinum and Clostridioides difficile). The BP2 digestate differed from those of the two other BPs with a higher nitrogen content, more total solids and greater abundance of Clostridia MBA03 and Disgonomonadacea. Persistence during digestion ranked from least to most, was: Campylobacter (1.6 to >2.9 log10 reduction, according to the BP) < E. coli (1.8 to 2.2 log10) < Salmonella (1.1 to 1.4 log10) < enterococci (0.2 to 1.2 log10) and C. perfringens (0.2 to 1 log10) < L. monocytogenes (-1.2 to 1.6 log10) < C. difficile and C. botulinum (≤0.5 log10). No statistical link was found between the reduction in the concentration of the targeted bacteria and the physicochemical and operational parameters likely to have an effect (NH3, volatile fatty acids and total solids contents, hydraulic retention time, presence of co-substrates), underlining the fact that the fate of the bacteria during mesophilic digestion depends on many interacting factors. The reduction in concentrations varied significantly over the sampling period, underlining the need for longitudinal studies to estimate the impact of AD on pathogenic microorganisms.

Rhizopus stolonifer biomass catalytic transesterification capability: optimization of cultivation conditions

BACKGROUND

Using fungal biomass for biocatalysis is a potential solution for the expensive cost of the use o enzymes. Production of fungal biomass with effective activity requires optimizing the cultivation conditions.

RESULTS

Rhizopus stolonifer biomass was optimized for transesterification and hydrolysis of waste frying oil (WFO). Growth and biomass lipolytic activities of R. stolonifer improved under shaking conditions compared to static conditions, and 200 rpm was optimum. As biomass lipase and transesterification activities inducer, olive oil was superior to soybean, rapeseed, and waste frying oils. Biomass produced in culture media containing fishmeal as an N-source feedstock had higher lipolytic capabilities than corn-steep liquor and urea. Plackett Burman screening of 9 factors showed that pH (5-9), fishmeal (0.25-1.7%, w/v), and KH2PO4 (0.1-0.9%, w/v) were significant factors with the highest main effect estimates 11.46, 10.42, 14.90, respectively. These factors were selected for response surface methodology (RSM) optimization using central composite design (CCD). CCD models for growth, biomass lipase activity, and transesterification capability were significant. The optimum conditions for growth and lipid modification catalytic activities were pH 7.4, fishmeal (2.62%, w/v), and KH2PO4 (2.99%, w/v).

CONCLUSION

Optimized culture conditions improved the whole cell transesterification capability of Rhizopus stolonifer biomass in terms of fatty acid methyl ester (FAME) concentration by 67.65% to a final FAME concentration of 85.5%, w/w.

Unraveling prevalence of homoacetogenesis and methanogenesis pathways due to inhibitors addition

Three inhibitors targeting different microorganisms, both from Archaea and Bacteria domains, were evaluated for their effect on CO₂ biomethanation: sodium ionophore III (ETH2120), carbon monoxide (CO), and sodium 2-bromoethanesulfonate (BES). This study examines how these compounds affect the anaerobic digestion microbiome in a biogas upgrading process. While archaea were observed in all experiments, methane was produced only when adding ETH2120 or CO, not when adding BES, suggesting archaea were in an inactivated state. Methane was produced mainly via methylotrophic methanogenesis from methylamines. Acetate was produced at all conditions, but a slight reduction on acetate production (along with an enhancement on CH₄ production) was observed when applying 20 kPa of CO. Effects on CO₂ biomethanation were difficult to observe since the inoculum used was from a real biogas upgrading reactor, being this a complex environmental sample. Nevertheless, it must be mentioned that all compounds had effects on the microbial community composition.

A state of the art review on the co-cultivation of microalgae-fungi in wastewater for biofuel production

The microalgae have a great potential as the fourth generation biofuel feedstock to deal with energy crisis, but the cost of production and biomass harvest are the major hurdles in terms of large scale production and applications. Using filamentous fungi to culture targeted alga for biomass accumulation and eventually harvesting is a sustainable way to mitigate environmental impacts. Microalgal co-culture method could be an alternative to overcome limitations and increase biomass yield and lipid accumulation. It was found to be the high feasibility for the production of biofuels from fungi and microalgae using wastewater. This article aimed to state the synergistic approaches, their culture protocols, harvesting procedure and their potential biotechnological applications. Additionally, algal-fungal consortia could digest cellulosic biomass, potentially reducing operating costs as part of industrial need. As a result of co-cultivation, biofuel production could be economically feasible owing to its excellent ability to treat wastewater and be eco-friendly. The implications of the innovative co-cultivation technology have demonstrated the potential for further development based on the policies that have been supported and implemented.

Nutrient removal from biogas slurry and biogas upgrading by microalgae-fungi-bacteria co-cultivation under different carbon nanotubes concentration

In this study, Chlorella vulgaris, Ganoderma lucidum, and endophytic bacteria were co-cultivated with the stimulation of strigolactone analogs GR24 to prepare pellets. During the purification of biogas slurry and biogas, multi-walled carbon nanotubes (MWCNTs) were introduced to enhance the removal efficiencies of nutrients and CO₂. The results showed that both GR24 and MWCNTs affected the purification of biogas slurry and biogas. The maximum chemical oxygen demand, total nitrogen, total phosphorus, and CO₂ removal efficiencies of the Chlorella vulgaris-Ganoderma lucidum-endophytic bacterial symbionts were 82.57 ± 7.96% (P < 0.05), 82.14 ± 7.87% (P < 0.05), 84.27 ± 7.96% (P < 0.05), and 63.93 ± 6.22% (P < 0.05), respectively, with the induction of 10^-9 M GR24 and 1 mg L^-1 MWCNTs. Moreover, the growth and photosynthetic performance of the symbionts were consistent with the removal effects. The Chlorella vulgaris-Ganoderma lucidum-endophytic bacterial symbionts obtained high growth rates and enzyme activity with the maximum growth rate of 0.365 ± 0.03 d^-1, mean daily productivity of 0.182 ± 0.016 g L^-1 d^-1, and carbonic anhydrase activity of 31.07 ± 2.75 units, respectively. These results indicated that an appropriate concentration of GR24 and MWCNTs could promote the growth of symbionts, reinforce the purification effects of biogas slurry and biogas, and provide a new idea for the simultaneous purification of wastewater and biogas.

Effect of GR24 concentrations on tetracycline and nutrient removal from biogas slurry by different microalgae-based technologies

A biogas slurry composed of carbon, nitrogen, phosphorus, and antibiotics was generated. Investigations into the nutrient and tetracycline removal performance of four microalgae-based contaminant removal technologies, including Chlorella vulgaris, C. vulgaris co-cultured with endophytic bacteria, C. vulgaris co-cultured with Ganoderma lucidum, and C. vulgaris co-cultured with G. lucidum and endophytic bacteria, were conducted. The algal-bacterial-fungal consortium with 10^-9 M strigolactone (GR24) yielded the maximum growth rate and average daily yield for algae at 0.325 ± 0.03 d^-1 and 0.192 ± 0.02 g L^-1 d^-1, respectively. The highest nutrient/ tetracycline removal efficiencies were 83.28 ± 7.95 % for chemical oxygen demand (COD), 82.62 ± 7.97 % for total nitrogen (TN), 85.15 ± 8.26 % for total phosphorus (TP) and 83.92 ± 7.65 % for tetracycline. Adding an algal-bacterial-fungal consortium with an optimal synthetic analog GR24 concentration is seemingly an encouraging strategy for enhancing pollutant removal by algae, possibly overcoming the challenges of eutrophication and antibiotic pollution.