Influence of acyl acceptor blends on the ester yield and fuel properties of biodiesel generated by whole-cell catalysis of cottonseed oil

Abstract

One of the promising alternatives to fossil fuels, biodiesel, is a renewable fuel which can be defined as methyl or ethyl ester of fatty acid made prominently from vegetable oils or animal fat. The present study outlines the observations on the fatty acid alkyl ester generation by transesterification of cottonseed oil using Aspergillus species as whole-cell biocatalyst. Current work also represents the difference in ester yield on the addition of alcohol blends with two different molar ratios (1:4 or 1:6). Further, the fuel properties viz., density, viscosity, gross calorific value, flash point, cloud point and pour point of ethyl-butyl and ethyl-propyl ester were analyzed, as per ASTM 6751. No significant difference was observed in ester yield with both the molar ratio of alcohols. Ester yield up to 91% and 87% was obtained using 1:4 and 1:6 M ratio respectively. By the use of a lower molar ratio (1:4) and whole-cell catalyst, a significant reduction in the cost of production of biodiesel is as expected. Alcohol other than ethanol facilitated only a marginal increase in ester yield with no significant variation from propanol to octanol. The fuel properties showed significant improvement in comparison to standard biodiesel. The use of whole cell bio-catalysis, as demonstrated in present study can be considered as a promising alternative to a chemical catalyst for the generation of long-chain fatty acid esters.