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Enhanced alcohol titre and ratio in carbon monoxide-rich off-gas fermentation of Clostridium carboxidivorans through combination of trace metals optimization with variable-temperature cultivation

Shen, Shaohuang, Gu, Yang, Chai, Changsheng, Jiang, Weihong, Zhuang, Yingping, Wang, Yonghong
Bioresource technology 2017 v.239 pp. 236-243
Clostridium, ammonium sulfate, biotransformation, butanol, carbon, cobalt, copper, fermentation, ferric chloride, gases, hexanols, nickel, temperature, zinc
Bioconversion of C1 gases to produce chemicals has good application prospects. Here, the combination of trace metals optimization using a statistical method with variable-temperature cultivation was used to enhance alcohol synthesis during CO-rich off-gas fermentation by Clostridium carboxidivorans P7. Based on ATCC medium 1754, the optimum concentration of the trace metals was found to be 5-fold Ni2+, Co2+, SeO42+, and WO42+; 3.48-fold Cu2+; 0.55-fold MoO42+; 0.5-fold Zn2+ and (NH4)2SO4·FeSO4·6H2O; and additional 44.32μM FeCl3·6H2O. The production of alcohol and organic acid changed to 4.40g/L and 0.50g/L from 2.16g/L and 2.37g/L, respectively, yielding an increase of alcohol-to-product ratio from 47.7% to 89.8%. By fermenting with the optimized medium and timed control of the incubation temperature (37°C [0–24h]–25°C [24–144h]), the alcohol titre further increased to 6.97g/L with 1.67g/L butanol and 1.33g/L hexanol, exceeding those previously reported for strain P7.