Trends in Carbon Dioxide (CO2) Fixation by Microbial Cultivations

Purpose of Review: Biological route is one of the viable options to mitigate CO2 from its point sources. The major purpose of the review article is to discuss the possible utilization of microbial cultures for the mitigation of CO2. The article also highlights the scaling-up approach for biological processes especially when microbial cultures are utilized for the same. Recent Findings: Few recent studies reported the chemoautotrophic fixation of CO2(g) by catalyzing thermodynamically favored but kinetically inhibited oxidation-reduction or electron donor-acceptor scheme of dissolved inorganic compounds. The previous studies have confirmed the utilization of different bacterial strains for the mitigation of 5%, 10%, and 15% CO2(g) in the absence of light and its simultaneous conversion into valuable products in the lab scale bioreactor. The recent studies also revealed the possibility of prokaryotes to assimilate CO2(g) via carbon concentration mechanism (CCM). Summary: The article summarizes the biological route for the natural assimilation of CO2(g) into biomass at the expense of very less energy penalty, via photoautotrophy and chemolithotrophy. The chemolithotrophs utilizes different concentrations of CO2 and thiosulfate salts as an energy source for the non-photosynthetic process. The identification of products using Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectroscopy (GCMS) studies is also entailed. The concept of material balance approach is explained to established the mechanism of CO2(g) mitigation through bacterial route. The obtained results pave the way for further development of CO2 utilization technology at larger scales. © 2020, Springer Nature Switzerland AG.