2.3.1. Microorganism
The organism used in this study was C. beijerinckii DSM 6422, obtained from the German collection of microorganisms (DSMZ, Leibniz, Germany). The strain was maintained on Reinforced Clostridial Medium, RCM, (Fluka, Sigma–Aldrich, Spain) in Hungate tubes (18 × 150 mm), in spore form and conserved at −20 °C under anaerobic conditions.