Genomic insights into clostridia in bioenergy production: Comparison of metabolic capabilities and evolutionary relationships.

Bacteria from diverse genera, including Acetivibrio, Bacillus, Cellulosilyticum, Clostridium, Desulfotomaculum, Lachnoclostridium, Moorella, Ruminiclostridium, and Thermoanaerobacterium, have attracted significant attention due to their versatile metabolic capabilities encompassing acetogenic, cellulolytic, and C1-metabolic properties, and acetone-butanol-ethanol fermentation. Despite their biotechnological significance, a comprehensive understanding of clostridial physiology and evolution has remained elusive. This study reports an extensive comparative genomic analysis of 48 fully sequenced bacterial genomes from these genera. Our investigation, encompassing pan-genomic analysis, central carbon metabolism comparison, exploration of general genome features, and in-depth scrutiny of Cluster of Orthologous Groups genes, has established a holistic whole-genome-based phylogenetic framework. We have classified these strains into acetogenic, butanol-producing, cellulolytic, CO2-fixating, chemo(litho/organo)trophic, and heterotrophic categories, often exhibiting overlaps. Key outcomes include the identification of misclassified species and the revelation of insights into metabolic features, energy conservation, substrate utilization, stress responses, and regulatory mechanisms. These findings can provide guidance for the development of efficient microbial systems for sustainable bioenergy production. Furthermore, by addressing fundamental questions regarding genetic relationships, conserved genomic features, pivotal enzymes, and essential genes, this study has also contributed to our comprehension of clostridial biology, evolution, and their shared metabolic potential.

Phytoremediation of toxic chemicals in aquatic environment with special emphasis on duckweed mediated approaches.

The discharge of toxic chemicals into water bodies and their linked detrimental effects on health is a global concern. Phytoremediation, an environment-friendly plant-based technology, has gained intensive interest over the last decades. For the aquatic phytoremediation process, the commonly available duckweeds have recently attracted significant attention due to their capacity to grow in diverse ecological niches, fast growth characteristics, suitable morphology for easy handling of biomass, and capacity to remove and detoxify various potential toxic elements and compounds. This review presents the progress of duckweed-assisted aquatic phytoremediation of toxic chemicals. A brief background of general phytoremediation processes, including the different phytoremediation methods and advances in understanding their underlying mechanisms, has been described. A summary of different approaches commonly practiced to assess the growth of the plants and their metal removal capacity in the phytoremediation process has also been included. A vast majority of studies have established that duckweed is an efficient plant catalyst to accumulate toxic heavy metals and organic contaminants, such as pesticides, fluorides, toxins, and aromatic compounds, reducing their toxicity from water bodies. The potential of this plant-based phytoremediation process for its downstream applications in generating value-added products for the rural economy and industrial interest has been identified.

Duckweed is an aquatic plant widely available in diverse ecosystems on the earth. Due to its fast growth in various environmental conditions, capacity to accumulate and transform different toxic chemicals, and a suitable morphology for handling and processing its biomass easily, duckweed has been projected as an efficient floating plant species for the aquatic phytoremediation technology. Moreover, the duckweed biomass generated from the post phytoremediation process may be transformed into various value-added products to support the rural economy.

Effect of electrode surface properties on enhanced electron transfer activity in microbial fuel cells.

The influence of electrode surface chemistry over biofilm growth was evaluated for photo-bioelectrocatalytic fuel cell. A consortium of photosynthetic bacteria was grown onto different electrodes designed with polyethylenimine (PEI) and multiwall carbon nanotubes as hydrophilic and hydrophobic modifier, respectively. The designed electrodes were loaded with 0.08, 0.17, and 0.33 µg/cm2 of PEI to change the hydrophilicity. However, 0.56, 0.72, and 0.83 mg/cm2 of multiwall carbon nanotubes were used to alter the hydrophobicity of the electrodes. The surface chemistry of electrode and bio-interaction was evaluated as a function of contact angle and biofilm formation. The results were compared with those obtained with a carbon paper electrode. The contact angle on the untreated electrode (carbon paper) was 118°, whereas for hydrophobic and hydrophilic electrodes, the maximum and minimum contact angles were 170° and 0°, respectively. Interestingly, the maximum biofilm growth (0.2275 g, wet basis) was observed on highly hydrophobic surface; however, the maximum electrochemical performance (246 mV) was shown by the most hydrophilic electrode surface. PEI-based electrode with good biofilm formation showed comparatively higher electrogenic activity.

Biofuel cell for generating power from methanol substrate using alcohol oxidase bioanode and air-breathed laccase biocathode.

We report here an alcohol oxidase (AOx) based third generation bioanode for generating power from methanol substrate in a fuel cell setup using air breathed laccase biocathode. A composite three dimensional microporous matrix containing multiwalled carbon nanotubes, carbon paste and nafion was used as electroactive support for immobilization of the enzymes on toray carbon paper as supporting electrode in the fabrication of the bioelectrodes. Polyethylenimine was used to electrostatically stabilize the AOx (pI 4.3) on the anode operating on direct electrochemistry principle. Osmium tetroxide on poly (4-vinylpyridine) was used to wire the laccase for electron transfer in the biocathode. The enzymatic biofuel cell (EFC) generated an open circuit potential of 0.61 (±0.02) V with a maximum power density of 46 (±0.002) µW cm(-2) at an optimum of 1M methanol, 25 °C and an internal resistance of 0.024 µΩ. The operation and storage half life (t1/2) of the EFC were 17.22 h and 52 days, respectively at a fixed load of 1.85 Ω. The findings have demonstrated the feasibility of developing EFC using AOx based bioanode and laccase based biocathode without applying any toxic free mediator and metal electrode supports for generating electricity.

Silk-fiber immobilized lipase-catalyzed hydrolysis of emulsified sunflower oil.

Lipase was immobilized in silk fibers through glutaraldehyde cross-linking to a maximum loading of 59 U/g silk-fiber and the immobilized lipase was utilized for the hydrolysis of sunflower oil (Helianthus annuus). The hydrolytic activity of the lipase, which was poor in biphasic oil in water system, was increased significantly when the sunflower oil was emulsified in aqueous medium. The hydrolytic activities of the immobilized lipase were 48.73 +/- 1.26 U, 36.11 +/- 0.96 U, and nil when the substrate sunflower oil was used as emulsion created by a rhamnolipid biosurfactant, Triton X100, and ultrasonication, respectively. Although the efficiency of the immobilized lipase was less than 12% than the corresponding free lipase, the immobilized lipase could be reused for the biosurfactant-mediated hydrolysis of sunflower oil up to third cycle of the reaction. The yield of the fatty acids in the second, third, and fourth cycles were 49.45%, 22.91%, and 5.09%, respectively, of the yield obtained in the first cycle.