发酵过程中酵母代谢产生的有机酸会影响发酵效率.以葡萄糖为底物,在自动发酵罐中进行了酿酒酵母间歇乙醇发酵实验,研究了发酵过程中酵母的主要代谢副产物中有机酸的种类及其对乙醇发酵的影响.结果表明,发酵过程中酵母代谢的主要有机酸是琥珀酸、乳酸和乙酸.3种酸的总量随温度(25~40℃)升高或pH增大(3~6)呈上升趋势,最大值可达5.78 g/L,占产物的23.3%.通过外源投加有机酸实验发现,3种代谢有机酸对酵母抑制作用的大小并不完全由其酸性决定,还与其进入细胞的难易程度等相关.通过外源投加有机酸实验结合发酵过程中去除有机酸实验可以确定,对乙醇发酵的影响由大到小依次为乙酸、琥珀酸和乳酸,且三者之间对乙醇发酵无明显的协同抑制效应.乙酸是发酵过程中产生主要抑制作用的代谢有机酸,2 g/L的乙酸可引起菌体浓度明显下降,4 g/L的乙酸即可引起乙醇得率下降86.7%.%The organic acids produced by Saccharomyces cerevisiae during the fermentation would affect the fermentation efficiency. Batch ethanol fermentation experiment was carried out in the automatic fermentation tank to study the mainly kinds of organic acids produced by yeast and their effects on fermentation. The results showed that succinate acid, lactic acid and acetic acid were the main organic acids produced by yeast during fermentation. The total amount of these acids increased with the increase of temperature from 25℃to 40℃or pH from 3 to 6, and the maximum value could be up to 5.78 g/L, accounting for 23.3% of all the products. By adding exogenous organic acids, it was found that their inhibition strength was not entirely decided by their acidity, also related to the degree of difficulty in entering the cells and other reasons. Combined with the experiment of removal organic acids during fermentation, it could be concluded that the effects of the three main metabolic organic acids on ethanol fermentation were different, from large to small were acetic acid, succinate, and lactic acid. And there was no obvious synergistic effect between the three acids. Acetic acid is the main inhibitors of metabolic by-product in the fermentation process, and it could cause cell concentration decreased significantly with 2 g/L, and ethanol yield fell by 86.7%with 4 g/L.
展开▼
