Renewable Hydrogen Production and Storage Via Enzymatic Interconversion of CO2 and Formate with Electrochemical Cofactor Regeneration

Green synthesis and characterization of iron nanoparticles synthesized from bioflocculant for wastewater treatment: A review

Nanotechnology is a rapidly expanding field with diverse healthcare, agriculture, and industry applications. Central to this discipline is manipulating materials at the nanoscale, particularly nanoparticles (NPs) ranging from 1 to 100 nm. These NPs can be synthesized through various methods, including chemical, physical, and biological processes. Among these, biological synthesis has gained significant attention due to its eco-friendly nature, utilizing natural resources such as microbes and plants as reducing and capping agents. However, information is scarce regarding the production of iron nanoparticles (FeNPs) using biological approaches, and even less is available on the synthesis of FeNPs employing microbial bioflocculants. This review aims to provide a comprehensive examination of the synthesis of FeNPs using microbial bioflocculants, highlighting the methodologies involved and their implications for environmental applications. Recent findings indicate that microbial bioflocculants enhance the stability and efficiency of FeNP synthesis while promoting environmentally friendly production methods. The synthesized FeNPs demonstrated effective removal of contaminants from wastewater, achieving removal rates of up to 93 % for specific dyes and significant reductions in chemical oxygen demand (COD) and biological oxygen demand (BOD). Additionally, these FeNPs exhibited notable antimicrobial properties against both Gram-positive and Gram-negative bacteria. This review encompasses studies conducted between January 2015 and December 2023, providing detailed characterization of the synthesized FeNPs and underscoring their potential applications in wastewater treatment and environmental remediation.

A Comprehensive Review of CO2 Hydrogenation into Formate/Formic Acid Catalyzed by Whole Cell Bacteria

The increasing levels of carbon dioxide (CO2) in the atmosphere, primarily due to the use of fossil fuels, pose a significant threat to the environment and necessitate urgent action to mitigate climate change. Carbon capture and utilization technologies that can convert CO2 into economically valuable compounds have gained attention as potential solutions. Among these technologies, biocatalytic CO2 hydrogenation using bacterial whole cells shows promise for the efficient conversion of CO2 into formate, a valuable chemical compound. Although it was discovered nearly a century ago, comprehensive reviews focusing on the utilization of whole-cell bacteria as the biocatalyst in this area remain relatively limited. Therefore, this review provides an analysis of the progress, strategies, and key findings in this field. It covers the use of living cells, resting cells, or genetically modified bacteria as biocatalysts to convert CO2 into formate, either naturally or with the integration of electrochemical and protochemical techniques as sources of protons and electrons. By consolidating the current knowledge in this field, this review article aims to serve as a valuable resource for researchers and practitioners interested in understanding the recent progress, challenges, and potential applications of bacterial whole cell catalyzed CO2 hydrogenation into formate.

Enzyme-accelerated CO2 capture and storage (CCS) using paper and pulp residues as co-sequestrating agents

In the present work, four CaCO3-rich solid residues from the pulp and paper industry (lime mud, green liquor sludge, electrostatic precipitator dust, and lime dregs) were assessed for their potential as co-sequestrating agents in carbon capture. Carbonic anhydrase (CA) was added to promote both CO2 hydration and residue mineral dissolution, offering an enhancement in CO2-capture yield under atmospheric (up to 4-fold) and industrial-gas mimic conditions (up to 2.2-fold). Geological CO2 storage using olivine as a reference material was employed in two stages: one involving mineral dissolution, with leaching of Mg2+ and SiO2 from olivine; and the second involving mineral carbonation, converting Mg2+ and bicarbonate to MgCO3 as a permanent storage form of CO2. The results showed an enhanced carbonation yield up to 6.9%, when CA was added in the prior CO2-capture step. The proposed route underlines the importance of the valorization of industrial residues toward achieving neutral, or even negative emissions in the case of bioenergy-based plants, without the need for energy-intensive compression and long-distance transport of the captured CO2. This is a proof of concept for an integrated strategy in which a biocatalyst is applied as a CO2-capture promoter while CO2 storage can be done near industrial sites with adequate geological characteristics.