纤维素乙醇生物加工过程中的抑制物对酿酒酵母的影响及应对措施

Inhibitors and their effects on Saccharomyces cerevisiae and relevant countermeasures in bioprocess of ethanol production from lignocellulose– a review

摘要:

以木质纤维素为原料生产乙醇, 预处理是必需的环节, 这一过程中不可避免产生了多种对微生物有抑制作用的化合物, 这些抑制物主要有3大类: 弱酸、呋喃醛类和酚类化合物。这些化合物影响后续乙醇发酵微生物酿酒酵母(Saccharomyces cerevisiae)的生长及发酵性能, 降低了乙醇的得率和产量, 是木质纤维素原料大规模生产乙醇的一个主要障碍。以下介绍了3类抑制物的形成及作用机制, 并介绍了应对抑制物作用、提高酵母发酵能力的措施及研究进展,包括发酵前预处理原料脱毒、通过进化工程驯化菌种或通过对抑制物耐受性相关基因的代谢工程操作提高酿酒酵母耐受性, 及通过发酵过程控制减少抑制物影响等。

Abstract:

The pretreatment of raw materials is necessary for ethanol production from lignocellulose, however, a variety of compounds which inhibit the fermenting microorganism such as Saccharomyces cerevisiae are inevitably formed in this bioprocess. Based on their chemical properties, the inhibitors are usually divided into three major groups: weak acids, furaldehydes and phenolic compounds. These compounds negatively affect the growth of S. cerevisiae, ethanol yield and productivity, which is one of the significant hurdles for the development of large-scale ethanol production from lignocellulose. We address here the origins of the three kinds of inhibitors and their mechanisms to S. cerevisiae. We also discuss the strategies of improving the fermentation performance of yeast, including detoxification of the pretreated substrates, enhancement of yeast tolerance and also fermentation control to reduce the effects of the inhibitors. The methods used in enhancing the yeast tolerance are traditional mutagenic breeding integrated with strains evolution under the suitable selective pressure, and metabolic engineering by introducing and/or overexpressing genes encoding enzymes such as furfural reductase, laccase and phenylacrylic acid decarboxylase, that confer the S. cerevisiae strains resistance towards specific inhibitors.