Effects of gas condition on acetic acid fermentation by Clostridium thermocellum and Moorella thermoacetica ( C. thermoaceticum )

Abstract

Fermentation with acetogens can be affected by cultivation gas phase, but to date, there is not enough evidence on that matter for Clostridium thermocellum and Moorella thermoacetica. In this work, the effects of sparged CO₂ as well as sparged and non-sparged N₂ on these microorganisms were studied using glucose and cellobiose as substrates. It was revealed that sparged CO₂ and non-sparged N₂ supported growth and acetic acid production by C. thermocellum and M. thermoacetica, while sparged N₂ inhibited both of the microorganisms. Notably, part of the sparged CO₂ was fermented by the co-culture system and contributed to an overestimation of the products from the actual substrate as well as an erring material balance. The best condition for the co-culture was concluded to be N₂ without sparging. These results demonstrate the importance of cultivation conditions for efficient fermentation by anaerobic clostridia species.

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