Continuous butanol and isopropanol production from sweet sorghum syrup with an immobilized Clostridium

Clostridium beijerinckii optinoii is a Clostridium species that produces butanol, isopropanol and small amounts of ethanol. Our previous studies have demonstrated a technically feasible continuous fermentation system for solvent production using immobilized Clostridium cells. In this study, instead of using the chemically defined glucose medium, processed syrup derived from sweet sorghum grown in south Louisiana will be used to continuously feed the immobilized Clostridium. The syrup contains 37.9% sucrose, 24.5% glucose, and 14.8% fructose (w/v). Parameters including starting sugar concentration and dilution rate will be tested. The Clostridium cells are expected to consume more than 80% of the fermentable sugars in the diluted syrup supplemented with invertase. Solvent concentration is expected to be higher than 10 g L^-1 with a butanol to isopropanol ratio between 2 and 3 (w/w). Solvent productivity is expected to be close to 1.0 g L^-1 h^-1. Continuous fermentation with immobilized cells will prove to be an effective and sustainable system for the conversion of syrup to useful solvents and fuels.