High‐rate continuous n‐butanol production by Clostridium acetobutylicum from glucose and butyric acid in a single‐pass fibrous‐bed bioreactor

• Published in: Biotechnology and bioengineering 2022-12, Vol.119 (12), p.3474-3486
• Main Authors: Chang, Wei‐Lun, Hou, Wenjie, Xu, Mengmeng, Yang, Shang‐Tian
• Format: Article
• Language: English
• Subjects: 1-Butanol; Acetone; acetone–butanol–ethanol fermentation; Bioreactors; Butanol; Butanols; Butyric Acid; Cell culture; Clostridium acetobutylicum; Contamination; continuous fermentation; Continuous production; Degeneration; Dilution; Ethanol; Fermentation; fibrous‐bed bioreactor; Glucose; Operating costs; Productivity; Washout
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.28223

Biobutanol produced in acetone–butanol–ethanol (ABE) fermentation at batch mode cannot compete with chemically derived butanol because of the low reactor productivity. Continuous fermentation can dramatically enhance productivity and lower capital and operating costs, but are rarely used in industrial fermentation because of increased risks of culture degeneration, cell washout, and contamination. In this study, cells of the asporogenous Clostridium acetobutylicum ATCC55025 were immobilized in a single‐pass fibrous‐bed bioreactor (FBB) for continuous production of butanol from glucose and butyrate at various dilution rates. Butyric acid in the feed medium helped maintaining cells in the solventogenic phase for stable continuous butanol production. At a dilution rate of 1.88 h−1, butanol was produced at 9.55 g/L, with a yield of 0.24 g/g and productivity of 16.8 g/L/h, which was the highest productivity ever achieved for biobutanol fermentation and an 80‐fold improvement over the conventional ABE fermentation. The extremely high productivity was attributed to the high density of viable cells (~100 g/L at >70% viability) immobilized in the fibrous matrix, which also enabled the cells to better tolerate butanol and butyric acid. The FBB was stable for continuous operation for an extended period of over 1 month. Continuous fermentation with clostridial cells immobilized in a single‐pass fibrous‐bed bioreactor (FBB) fed with media containing glucose and butyric acid as cosubstrates for stable high‐rate n‐butanol production. The high density of viable cells immobilized in the fibrous matrix allowed the FBB to be operated at a high dilution rate to achieve the highest butanol productivity (16.8 g/L/h) ever reported.