期刊
JOURNAL OF MICROBIOLOGY AND BIOTECHNOLOGY
卷 25, 期 6, 页码 837-844出版社
KOREAN SOC MICROBIOLOGY & BIOTECHNOLOGY
DOI: 10.4014/jmb.1408.08015
关键词
Bioethanol; carob pod; fermentation; invertase synthesis; Saccharomyces; second-generation biofuels
资金
- Project Alfaetilico, as part of the Portuguese National Program QREN-POAlgarve21
Carob waste is a useful raw material for the second-generation ethanol because 50% of its dry weight is sucrose, glucose, and fructose. To optimize the process, we have studied the influence of the initial concentration of sugars on the fermentation performance of Saccharomyces cerevisiae. With initial sugar concentrations (S-0) of 20 g/l, the yeasts were derepressed and the ethanol produced during the exponential phase was consumed in a diauxic phase. The rate of ethanol consumption decreased with increasing S-0 and disappeared at 250 g/1 when the Crabtree effect was complete and almost all the sugar consumed was transformed into ethanol with a yield factor of 0.42 g/g. Sucrose hydrolysis was delayed at high S-0 because of glucose repression of invertase synthesis, which was triggered at concentrations above 40 g/1. At S-0 higher than 250 g/1, even when glucose had been exhausted, sucrose was hydrolyzed very slowly, probably due to an inhibition at this low water activity. Although with lower metabolic rates and longer times of fermentation, 250 g/1 is considered the optimal initial concentration because it avoids the diauxic consumption of ethanol and maintains enough invertase activity to consume all the sucrose, and also avoids the inhibitions due to lower water activities at higher S-0.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据