半纤维素水解液中抑制物对发酵生产木糖醇的影响

以木糖为底物发酵生产木糖醇,考察了葡萄糖、阿拉伯糖、果糖等半纤维素糖类对木糖醇发酵动力学行为的影响,并确定了适宜起始木糖质量浓度为100 g/L.当发酵液中乙酸与糠醛的质量浓度分别超过1 g/L时,抑制作用逐渐增强,通过调节半纤维素水解液的起始pH值从4.0到6.0,可有效减轻乙酸对发酵的抑制作用.适量的K+、Mg2+、Na+等微量元素和H2PO4-离子对酵母具有较强的代谢调控作用,其中以Mg2+的影响最为显著.无机盐质量浓度在0～4 g/L内有利于木糖醇发酵.以合成培养基为底物发酵生产木糖醇,与半纤维素水解液的发酵结果相比,两者的动力学曲线较为符合,为进一步研究木糖醇发酵动力学提供了实验依据.

Effects of inhibitors in hemicellulosic hydrolysate on xylitol production

The influences of xylose, glucose, arabinose, fructose and the inhibitors from corn cob hemicellulosic hydrolysate on xylitol production by Candida sp. were investigated. The optimum initial xylose concentration in the culture media was about 100g/L. The inhibitions of acetic acid and furfural in the hydrolysate increased gradually when their concentrations exceeded 1g/L. An increase in the initial pH value from 4.0 to 6.0 effectively reduced the inhibition of acetic acid. A moderate concentration of K~ , Mg~(2 )(especially), Na~ and H_2PO_4~- enhanced xylitol fermentation. When the salt concentration of 0~4g/L, both the cell growth and the fermentation were strongly suppressed. Synthetic media composed of hemicelluosic sugars were used for xylitol fermentation. The time course of xylitol fermentation on synthetic media was in good agreement with that on the hydrolysate. The results can greatly facilitate further study on the kinetics of xylitol fermentation from hemicellulosic hydrolysate.