Capnophilic Lactic Fermentation in Thermotoga sp. strain RQ7: a shift from dark fermentation

Abstract

The marine hyperthermophilic bacterium Thermotoga neapolitana operates a variant of Dark Fermentation pathway, named capnophilic (CO2-requiring) lactic fermentation (CLF). Sparging of CO2 induces the metabolic shift to the novel pathway resulting in the production of molecular hydrogen and non-competitive synthesis of L-lactic acid. These characteristics make CLF fermentation of great biotechnological interest and a cost-effective production method. The objective of this master’s thesis project was to perform a detailed characterization of CLF in Thermotoga sp. strain RQ7. Growth parameters and fermentation products were measured every 6 hours after initially sparging a bacterial culture with CO2. The total fermentation time was 36 hours. Genomic expression of key CLF enzymes, such as PFOR, HYD, LDH, RNF, NFN, V-ATPase and F-ATPase were investigated by real-time PCR, and key protein expression, such as HYD, PFOR, V-ATPase, and F-ATPase, is reported using western blot analysis.