Mixotrophic co-cultures fermentation of C1-gases and carrot discard hydrolysate by C. carboxidivorans and C. beijerinckii in stirred tank bioreactor and gas-lift bioreactor

Abstract

The current study represents the bioconversion of C1 gases (CO and CO2) using co-cultures of Clostridium car- boxidivorans and Clostridium beijerinckii, with hydrolysates from carrot discard as a co-substrate and supplemental Fe0. The performance of two distinct bioreactor configurations, a stirred-tank bioreactor (STB) and a gas-lift bioreactor (GLB) was compared under various gas flow rates. The GLB technology, operating at a gas flow of 50 mL/min, proved more efficient, yielding up to 12.0 g/L of butanol, 2.7 g/L of acetic acid, and 7.4 g/L of butyric acid within a 47 h fermentation period. This process achieved complete consumption of sugars and CO, alongside a maximum CO2 uptake of 82.4 % at t = 33 h. Consequently, the gas-lift bioreactor represents a promising strategy for the co-fermentation of C1 gases and carrot discard hydrolysate by C. carboxidivorans and C. beijerinckii, offering low energy requirements, cost-effectiveness, and simplicity in design and operation.