Isopropanol-butanol-ethanol production by cell-immobilized vacuum fermentation

The Isopropanol-Butanol-Ethanol productivity by solventogenic clostridia can increase when cells are immobilized on low-cost, renewable fibrous materials; however, butanol inhibition imposes the need for dilute sugar solutions (less than40 g/L). To alleviate this problem, the in-situ vacuum product recovery technique was applied to recover IBE in repeated-batch cultivation of Clostridium beijerinckii DSM 6423 immobilized on sugarcane bagasse. Five repeated batch cycles were conducted in a 7-L bioreactor containing P2 medium (-60 g/L glucose) and bagasse packed in 3D-printed concentric annular baskets. In three cycles, glucose was consumed by 86% on average, the IBE productivity was 0.35 g/L center dot h or 30% and 17% higher relative to free-and immobilized (without vacuum)-cell cultures. Notably, the product stream contained 45 g/L IBE. However, the fermentation was unsatisfactory in two cycles. Finally, by inserting a fibrous bed with hollow annuli in a vacuum fermentation, this work introduces the concept of an internal-loop boiling-driven fibrous-bed bioreactor.

Automated summary

The productivity of Isopropanol-Butanol-Ethanol can be increased by immobilizing cells on low-cost, renewable fibrous materials, with in-situ vacuum product recovery technique applied for repeated-batch cultivation. The fermentation process showed improved IBE productivity compared to free- and immobilized-cell cultures, with the product stream containing 45 g/L IBE. However, unsatisfactory results were obtained in two cycles, leading to the introduction of a concept of an internal-loop boiling-driven fibrous-bed bioreactor.