Gadgil C J, Bhat P J, Venkatesh K V
Department of Chemical Engineering and Biotechnology Center, Indian Institute of Technology, Bombay, Mumbai, India.
Biotechnol Prog. 1996 Nov-Dec;12(6):744-50. doi: 10.1021/bp9600804.
Cybernetic modeling has traditionally been used in the modeling of microbial growth on multiple substrates. In this paper, cybernetic modeling has been applied to serve as a model for growth on substrates such as melibiose, which are disaccharides and enzymatically degrade to a monosaccharide mixture in the fermentation broth. The enzyme alpha-galactosidase has been shown to be strongly induced in the presence of galactose and severely repressed by glucose. In the present model, the relative concentration of alpha-galactosidase has been linked to that of the key enzyme for galactose metabolism. The enzymatic degradation process is placed under the control of the cybernetic variables. The maximum rate of melibiose degradation vm and the Monod parameters for growth of Saccharomyces cerevisiae on pure glucose and galactose were estimated by batch growth experiments. S. cerevisiae growth on melibiose and a mixture of melibiose and glucose under a variety of preculturing conditions was simulated. Depending on the rate of enzymatic degradation (i.e., the value of vm), the cell mass profile for microbial growth on a disaccharide can resemble profiles for growth on a single substrate (melibiose) or can resemble diauxie growth. Experiments indicate that the model is able to accurately predict the cell mass profiles for yeast growth.
控制论建模传统上一直用于多种底物上微生物生长的建模。在本文中，控制论建模已被应用于作为在诸如蜜二糖等底物上生长的模型，蜜二糖是二糖，在发酵液中酶解为单糖混合物。已表明α-半乳糖苷酶在半乳糖存在下被强烈诱导，而被葡萄糖严重抑制。在当前模型中，α-半乳糖苷酶的相对浓度已与半乳糖代谢关键酶的浓度相关联。酶解过程置于控制论变量的控制之下。通过分批生长实验估计了酿酒酵母在纯葡萄糖和半乳糖上生长的蜜二糖最大降解速率vm和莫诺德参数。模拟了酿酒酵母在蜜二糖以及在各种预培养条件下蜜二糖与葡萄糖混合物上的生长情况。根据酶解速率（即vm的值），二糖上微生物生长的细胞质量曲线可能类似于单底物（蜜二糖）上的生长曲线，也可能类似于二次生长曲线。实验表明该模型能够准确预测酵母生长的细胞质量曲线。
