Enhancement of nitrate removal and electricity generation in microbial fuel cell using eggshell supported biocathode

Integration of biocompatible hydrogen evolution catalyst developed from metal-mix solutions with microbial electrosynthesis

Microbial conversion of CO2 to multi-carbon compounds such as acetate and butyrate is a promising valorisation technique. For those reactions, the electrochemical supply of hydrogen to the biocatalyst is a viable approach. Earlier we have shown that trace metals from microbial growth media spontaneously form in situ electro-catalysts for hydrogen evolution. Here, we show biocompatibility with the successful integration of such metal mix-based HER catalyst for immediate start-up of microbial acetogenesis (CO2 to acetate). Also, n-butyrate formation started fast (after twenty days). Hydrogen was always produced in excess, although productivity decreased over the 36 to 50 days, possibly due to metal leaching from the cathode. The HER catalyst boosted microbial productivity in a two-step microbial community bioprocess: acetogenesis by a BRH-c20a strain and acetate elongation to n-butyrate by Clostridium sensu stricto 12 (related) species. These findings provide new routes to integrate electro-catalysts and micro-organisms showing respectively bio and electrochemical compatibility.

Eggshells & Eggshell Membranes- A Sustainable Resource for energy storage and energy conversion applications: A critical review

As the world strives to achieve a sustainable future, the exploration of alternative and renewable raw materials for energy storage and energy conversion has gained significant attention. A growing trend on "Waste to Energy" approach has attained prominence. Accordingly, chicken eggshells, a residual from poultry industry, have emerged as a promising candidate due to their abundant availability, low cost, and unique physical and chemical properties. This review article presents an overview of recent advancements in utilizing eggshell waste for energy storage and energy conversion applications. It discusses the transformation of eggshells usage into functional materials, along with their performance in various energy-related applications. The potential of eggshell-based materials in improving energy efficiency and reducing environmental impact is highlighted, providing insights into the future prospects of this sustainable resource.

Simultaneous denitrification and electricity generation in a methane-powered bioelectrochemical system

Bioelectrochemical system is a novel method for controlling down nitrate pollution, yet the feasibility of using methane as the electron donors for denitrification in this system remains unknown. In this study, using the effluent from mother BESs as inocula, a denitrifying anaerobic methane oxidation bioelectrochemical system was successfully started up in 92 days. When operated with 50 mmol/L phosphate buffer solution at pH 7 and 30°C, the maximum methane consumption, nitrate, and total nitrogen removal load reached 0.23 ± 0.01 mmol/d, 551.0 ± 22.1 mg N/m3 /d, and 64.0 ± 18.8 mg N/m3 /d, respectively. Meanwhile, the peak voltage of 93 ± 4 mV, the anodic coulombic efficiency of 6.99 ± 0.20%, and the maximum power density of 219.86 mW/m3 were obtained. The metagenomics profiles revealed that the dominant denitrifying bacteria in the cathodic chamber reduced most nitrate to nitrite through denitrification and assimilatory reduction. In the anodic chamber, various archaea including methanotrophs and methanogens converted methane via reverse methanogenesis to form formate (or H2 ), acetate, and methyl compounds, which were than utilized by electroactive bacteria to generate electricity. PRACTITIONER POINTS: A denitrifying anaerobic methane oxidation BES was successfully started up in 92 d. Simultaneous removal of methane and nitrate was achieved in the DAMO-BES. Functional genes related to AMO and denitrification were detected in the DAMO-BES. Methylocystis can mediate AMO in the anode and denitrification in the cathode.

Significance of microbial genome in environmental remediation

Environmental pollutants seriously threaten the ecosystem and health of various life forms, particularly with the rapid industrialization and emerging population. Conventionally physical and chemical strategies are being opted for the removal of these pollutants. Bioremediation, through several advancements, has been a boon to combat the existing threat faced today. Microbes with enzymes degrade various pollutants and utilize them as a carbon and energy source. With the existing demand and through several research explorations, Genetically Engineered Microorganisms (GEMs) have paved to be a successful approach to abate pollution through bioremediation. The genome of the microbe determines its biodegradative nature. Thus, methods including pure culture techniques and metagenomics are used for analyzing the genome of microbes, which provides information about catabolic genes. The information obtained along with the aid of biotechnology helps to construct GEMs that are cost-effective and safer thereby exhibiting higher degradation of pollutants. The present review focuses on the role of microbes in the degradation of environmental pollutants, role of evolution in habitat and adaptation of microbes, microbial degenerative genes, their pathways, and the efficacy of recombinant DNA (rDNA) technology for creating GEMs for bioremediation. The present review also provides a gist of existing GEMs for bioremediation and their limitations, thereby providing a future scope of implementation of these GEMs for a sustainable environment.