关键词: 半纤维素水解液, 抑制物, 丁醇发酵, 代谢相关基因

Abstract: Due to the toxicity of inhibitors in hemicellulose hydrolysate to microorganism,hemicellulose hydrolysate cannot be directly used as substrate for butanol fermentation. The effects of inhibitors to non-anaerobic butanol-producing symbiotic system TSH06 was studied,aiming at laying the foundation for the butanol fermentation using hydrolysate without detoxification. Hemicellulose hydrolysate of corncob diluted with P2 medium was used as substrate in butanol fermentation. The pH of culture media was adjusted to be neutral with NaOH and ammonia respectively. The inhibition effect of the hydrolysate on TSH06 was studied by qPCR with gene primes of key enzymes. Results showed that the existence of Na⁺ inhibited the growth of TSH06. Furthermore,TSH06 grew and fermented in 50% or lower degrees of diluted hemicellulose hydrolysate,tolerated and degraded the furfural and 5-HMF,and the ultimate butanol concentration reached 4.16-5.16 g/L,lower than that in P2 medium（butanol concentration of 8.83 g/L）. In diluted hemicellulose hydrolysate,acetic acid concentration remained above 3.18 to 4.16 g/L after 48 h,much higher than that in P2 medium（<2 g/L）. Compared with P2 medium,the transcription ratio of key genes in the organic acid production pathway rose significantly while TSH06 in the 50% hemicellulose hydrolysates and declined significantly in the organic acid reflux pathway and butanol production pathway. In conclusion,excessive acetic acid in the hemicellulose hydrolysate might damage cells and block the transition from acidogenesis phase to solventogenesis phase. As the accumulation of acid,bacterial cells tend to decline and death before the substrate is completely consumed,leading to the reduction of butanol production and the substrate is not fully utilized.

Key words: hemicellulose hydrolysate, inhibitor, butanol fermentation, metabolism related genes