Logistic模型模拟乙醇发酵产物动力学

乙醇发酵产物动力学的研究有助于更好的认识发酵过程,为其工业放大及生产操作条件的优化提供理论基础。基于Logistic方程的菌体生长动力学模型可较好的描述细胞生长期及细胞自身抑制作用,但由于该模型方程中的比例参数与积分常数没有明显的生物学意义,使其应用受到了限制。该文从生物学与化学工程学结合角度对Logistic模型方程重新参数化,将发酵产物乙醇生成动力学与酵母生长动力学方程类比,给出了乙醇浓度的显式函数模型,模型中不再出现酵母菌浓度变量,大大简化了模型,并且赋予参数其物理意义;在研究了以葡萄糖和玉米淀粉为原料乙醇质量浓度、总糖质量浓度在不同底物质量浓度和料液比条件下随发酵时间的变化规律的基础上运用该模型拟合了以葡萄糖和玉米淀粉为原料进行乙醇发酵的试验数据,结果表明:模型值与试验数据具有较好一致性,拟合度均大于0.97,可见该重新参数化的Logistic模型可以描述发酵生产乙醇过程中产物乙醇的动力学行为,具有预测工业上实际发酵过程中乙醇浓度的潜力。

Product kinetics of Logistic model to simulate ethanol fermentation

Abstract: Ethanol plays an important role in the national economy, and is widely used in the raw materials of food, medicine, and the chemical industry. In recent years, with the challenge facing the world's energy security, more and more attention has been devoted to the conversion of biomass into fuel ethanol. Ethanol is considered to be a renewable and clean fuel, which can be an alternative to fossil fuels. So far, compared with other ethanol production methods, the fermentation method to produce ethanol has so many advantages, such as green environmental protection and low cost, that attracts lots of researchers' attention. There are many influence factors in the fermentation process, which make the fermentation process so complicated that it is hard to be controlled. The variation of the ethanol concentration with different fermentation times is directly related to the fermentation results. How to get higher ethanol concentration by a fermentation method has become the hot and difficult issue of the fermentation field. The research of ethanol fermentation kinetic is beneficial for understanding the fermentation process. It provides a theoretical basis for the amplification and optimization of fermentation industry. A bacteria growth dynamics model based on a Logistic equation can better describe the cell growth and inhibition; however, because the parameters and the integral constant of the model equation have no obvious biological significance, its application is limited. To establish a practical product kinetic model of ethanol fermentation, in this article, a reparameterized Logistic model was applied to correlate the ethanol concentration and time in the fermentation process, which was obtained by the analogy of the yeast growth. That is, an explicit function of ethanol concentration is given, which can combine biology and chemical engineering. As there was no yeast concentration in the model, the model was simplified so much and the parameters of it have an immediate physical interpretation that can be conveniently applied in industry. Through the research on glucose and corn starch as the raw material for ethanol fermentation, we studied the variation of ethanol concentration, total sugar concentration with time under the condition of different substrate quality, and the ratio of material to water. Then the experimental data were correlated by the reparameterized Logistic model in ethanol fermentation with glucose and corn starch. The model parameters and the consistency were good between the model and the experiments, the degree of fitting R2, was greater than 0.97. The results showed that the model can be used to represent the kinetics behavior of ethanol concentration in fermentation, which has the potential to predict ethanol concentration in industrial fermentation.