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Photosensitization of electro-active microbes for solar assisted carbon dioxide transformation

Kumar, Manoj, Sahoo, Prakash C., Srikanth, Sandipam, Bagai, Reshmi, Puri, S.K., Ramakumar, S.S.V.
Bioresource technology 2019 v.272 pp. 300-307
acetic acid, bacteria, cadmium, carbon dioxide, cysteine, harvesting, hexanoic acid, hydrogen sulfide, methanol, photosensitivity, semiconductors, sulfur
Tandem bio-inorganic platform by combining efficient light harvesting properties of nano-inorganic semiconductor cadmium sulfide (CdS) with biocatalytic ability of electro-active bacteria (EAB) towards carbon dioxide (CO2) conversion is reported. Sulfur was obtained from either cysteine (EAB-Cys-CdS) or hydrogen sulfide (EAB-H2S-CdS) and experiments were carried out under similar conditions. Anchoring of the nano CdS cluster on the microbe surface was confirmed using electronic microscope. Bio-inorganic hybrid system was able to produce single and multi-carbon compounds from CO2 in visible spectrum (λ > 400 nm). Though, acetic acid was dominant (EAB-Cys-CdS, 1.46 g/l and EAB-H2S-CdS, 1.55 g/l) in both the microbe-CdS hybrids, its concentration as well as product slate varied significantly. EAB-H2S-CdS produced hexanoic acid and less methanol fraction, while the EAB-Cys-CdS produced no hexanoic acid along with almost double the concentration of methanol. Due to easy harvesting process, this bio-inorganic hybrid represents unique sustainable approach for solar-to-chemical production via CO2 transformation.