초록
<P><B>Abstract</B></P> <P>Experimental data of ethanol fermentation in a two-tank system with cell recycling using sucrose as a substrate were investigated to establish a kinetic model that described the reaction. Flocculent yeast <I>Saccharomyces diastaticus</I> LORRE-316 was used as the fermenting yeast, and the fermentation medium comprised 80 g/L sucrose, 10 g/L yeast extract, 10 g/L peptone, 2 g/L potassium phosphate monobasic (KH<SUB>2</SUB>PO<SUB>4</SUB>), and 0.5 g/L magnesium sulfate heptahydrate (MgSO<SUB>4</SUB>·7H<SUB>2</SUB>O). Three models, the Monod model, the modified Monod model, and the extended-modified Monod model, were used to describe fermentation, and the extended-modified Monod model described the reaction more accurately than the other two models. The model took substrate limitations plus substrate and ethanol inhibitive effects into consideration, and was modified to include assumptions that included terms for substrates (sucrose, glucose and fructose) and product (ethanol). In addition, the ethanol concentration had a significant effect on cell growth. The results of Lineweaver–Burk plots showed that the maximum specific growth rate (μ<SUB> <I>MAX</I> </SUB>) and the Monod constant (<I>K<SUB>S</SUB> </I>) were 0.72/h and 26.77 g/L, respectively. The models were suitable for describing the experimental data.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Deliver kinetic modeling of producing ethanol using <I>Saccharomyces diastaticus</I> LORRE316 in a two-tank continuous fermentation system. </LI> <LI> Model giving information of the interaction of different sugar sources in sugar fermentation by using <I>Saccharomyces diastaticus</I>. </LI> <LI> Developed three different models to describe the mechanism of ethanol production process. </LI> <LI> Found the best mechanism to descript the ethanol fermentation using yeast <I>Saccharomyces diastaticus</I> LORRE316 in two-tank system. </LI> <LI> The model give a good result and prove to be able to predict the conversion of bioethanol from the production process. </LI> </UL> </P> <P><B>Graphical abstracts</B></P> <P>There were limited numbers of mathematical models for fermentation of sugar to ethanol by using <I>Saccharomyces diastaticus</I> LORRE-316 in previous works. Also, there were still significant discrepancy between the experimental results and their mathematic modeling. There is also no mathematical model express the fermentation reaction of sugar to ethanol by using <I>Saccharomyces diastaticus</I> LORRE-316 in continuous reactor. Therefore, the mathematical for continuous reactor is firstly derived here. Also, in this work, with mechanism derived, the gaps between the experimental data and model are closed. Therefore, the mechanism derived in this work is more rectified. The kinetic parameters also derived in this work. In this model, the priority of sugar utilization was considered. We found that glucose is more prioritize than fructose and sucrose. The inhibition factor of fructose utilization by glucose was represented as the concentration of glucose (<I>1–G/G<SUB>0</SUB> </I>).</P> <P>Experimental data and results of the modified model of ethanol production (Solid line: Model)</P> <P>Figure shows the concentration profiles of the substrates and product in ethanol fermentation generated. At the initial stage, the concentration of glucose and fructose continuously decreased with time. No evident decrease in the concentration of sucrose was reported during this time, indicating that the utilization of glucose and fructose was competitive for sucrose utilization. Hence, the cells used glucose and fructose before sucrose. As the concentration of glucose and fructose reached almost zero, the concentration of sucrose decreased rapidly with time, which confirmed the effect of glucose and fructose concentration on sucrose utilization. With time, the concentration of ethanol increased with the increase in the utilization o