70 / 2023-05-31 21:26:48

Making single-cell protein from waste-derived syngas: the bioconversion of carbon monoxide

Syngas; Carbon monoxide; Hydrogen-oxidizing bacteria; Carboxydobacteria; Single-cell protein; Amino acid

Syngas, derived from residual biomass, is a renewable source for the biomanufacturing of diverse valued products. While H₂ and CO₂ in the syngas can be easily utilized by hydrogen oxidizing bacteria (HOB) to produce single cell protein (SCP), the direct bioconversion of CO which is the major component of syngas is rarely reported. In this study, the capability of a carboxydobacteria species, Pseudomonas carboxydohydrogena Z-1062, for the production of SCP using CO as substrate was evaluated. Different syngas compositions were set up for P. carboxydohydrogena Z-1062 growth, with CO content up to 57.14%. Besides, ammonium and nitrate were found both valid nitrogen sources for P. carboxydohydrogena Z-1062 and the protein contents in biomass were 63.91% and 50.31%, respectively. Up to 16-18 amino acids were detected in the harvested biomass. Moreover, higher shaking frequency promoted a higher bacterial growth rate. Furthermore, H₂ and O₂ generated from solar-powered water splitting were established as the efficient electron donor and acceptor for the P. carboxydohydrogena Z-1062 to oxidize CO. This study demonstrates that waste-derived syngas is an alternative and promising substrate for SCP synthesis, offering a new strategy for the integration of waste biomass and renewable energy to produce human food or animal feed.