Role of microbubbles coupling fibrous-bed bioreactor in butyric acid production by Clostridium tyrobutyricum using Brewer's spent grain as feedstock

摘要

Microbubbles coupling fermentation is an efficient technology for improving oxygen transfer to aerobic microorganisms in a bioreactor containing an air sparger. However, the effect of this technology on anaerobic Clostridium tyrobutyricum, whose morphology develops viscous broth rheology and lumps impeding the nutrient mass transfer, has not been reported yet. Therefore, we evaluated the role of microbubbles coupling fibrous-bed bioreactor (MBFBB) on butyrate production by immobilized Clostridium tyrobutyricum cells obtained from renewable feedstock brewer's spent grain (BSG). Compared with the conventional fibrous-bed bioreactor (FBB) fermentation, two-fold shorter fermentation time and two-fold higher butyrate productivity were achieved by MBFBB-immobilized C. tyrobutyricum cells. Furthermore, long-term stability and reliability for butyrate production were obtained in ten cycle process using BSG hydrolysate. Finally, fed-batch fermentation using BSG hydrolysate produced a high butyrate titer of 43.68 g/L, with a significantly higher selectivity of 11.67, reducing the production cost of downstream processing. The results also indicated that butyrate productivity of 5.40 g/(L h were successfully obtained in BSG medium, thereby representing the highest productivity reported to date in C. tyrobutyricum from low-cost feedstocks. To our knowledge, this is also the first report related to microbial production of butyrate from BSG. Based on techno-economic analysis, it was demonstrated that the MBFBB-based fermentation process with BSG, was robust, economic and should underpin the future development of commercial biobutyrate production.