Kinetic study of starch enzymatic hydrolysis by Aspergillus niger and ethanol production by Saccharomyces cerevisiae

The use of biological processes and optimizing them in order to produce biofuels such as ethanol is very important due to economic and environmental issues. Therefore, this study was conducted to investigate the kinetic model of starch enzymatic hydrolysis by Aspergillus niger and ethanol production using Saccharomyces cerevisiae. The study was performed on a laboratory scale. The effect of different parameters such as pH and temperature on starch enzyme hydrolysis by A. niger was investigated. Also, the Michaelis-Menten’s model was used to assess the Kinetic model of the enzymatic hydrolysis process. In order to produce ethanol from the hydrolyzed starch, S. cerevisiae (yeast) was used at the temperature of 25 °C and pH of 4.5. The results showed that the pH of 5 and the temperature of 35 °C have the highest effect on glucose production by A. niger. In addition, assessment of the kinetics and the constants of the model measured Vmax and Km as 10.41 and 73.23, respectively. Comparison between the experimental data and those predicted from the rate model indicated good agreement (R2= 0.93). The results of ethanol production by S. cerevisiae on hydrolyzed medium with glucose initial concentration of 32 g/l showed the maximum ethanol production and cell dry weight as 10.04 g/l and 3.08 g/l, respectively. According to the results of this study Michaelis–Menten kinetics model is able to predict enzymatic hydrolysis of starch. Furthermore, hydrolyzed starch can be used as an appropriate substrate for ethanol production.