Monday, April 29, 2013
Exhibit Hall
Factorial designs commonly applied to model esters yield use conditions at the end of the reaction that are associated with the highest yields. In these conditions inhibitory enzymatic effects or limitations of kinetic equilibrium have already occurred. It becomes then difficult to understand the effect of each variable, for example, at the beginning of the reaction. A suitable oil:alcohol molar ratio may contribute favorably for the reaction rate and reduces diffusional limitations of the system, but can also cause enzyme inhibition. A suitable temperature can cause an enzymatic activation, but may also reduce the stability of the enzyme during the reaction. The appropriate amount of enzyme in the reaction medium is an important economic factor, providing higher yields per volume, and however it can also cause difficult access of the substrate to the active site. Diverging from the common trend we determined the influence of the variables molar ratio oil:alcohol, temperature and amount of enzyme and their interactions during the development of the reaction. The results of a full 23 factorial design show that the significance of the variables is different throughout the reaction. In the reaction conducted, between 0 and 60 min the molar ratio of oil:alcohol is the most important variable. Between 90 and 120 min, in addition to the oil:alcohol molar ratio, the amount of enzyme has significant influence on the reaction. Towards the end of the reaction, up to 4320 min, the temperature gradually becomes the variable that most strongly impacts the yield of esters.