Читать книгу Biodiesel Technology and Applications - Группа авторов - Страница 25

Use of enzyme in any chemical reaction makes the reaction less energy intensive, but, like every other chemical reaction, increase in temperature enhances reaction speed and rate. Similarly, in case of enzymatic biodiesel production, increase in temperature increases enzyme activity, reaction speed, its rate, and production yield [45]. When Lipozyme TL IM lipase was used to transesterify crude palm oil using methanol then the resulting FAME yield was 96.15% and 85.86% at 40°C and 30°C, respectively [95, 96]. But this effect is limited to certain extent because beyond enzyme optimum temperature, enzyme structure becomes unstable and that leads to enzyme denaturation and reaction becomes slower and yield also decreases. Novozym 435 catalyzed biodiesel production from microalgal lipids, there was 19% decrease in product yield when temperature went from 45°C to 55°C, i.e., higher than optimum temperature [97, 98]. Enzyme temperature should remain below the boiling point of alcohols being used in the reaction system to avoid evaporation of alcohol. In case of methanol and ethanol-mediated transesterification, reaction temperature is 65°C and 78°C, respectively [8]. Free bacterial lipases are considered thermally stable but if they get immobilized thermal stability increases [45]. Optimum enzyme temperature is influenced by lipase thermal stability, type of solvent, alcohol-to-oil molar ratio, and lipase immobilization. Every enzyme has different optimum temperature depending on the source and type of enzyme. Normally, lipases have optimum temperature range that is 20°C–70°C. Optimum temperature for C.antartica lipase is 40°C [99, 100].