Assessment of waste frying oil transesterification capacities of local isolated Aspergilli species and mutants

Abstract

Biodiesel (fatty acids methyl esters, FAME) has attracted considerable attention as an environmentally and eco-friendly alternative for diesel engines. This research manipulates the use of Aspergillus whole-cell lipase as a biocatalyst for biodiesel production from waste frying oil (WFO). A total of 17 isolates of Aspergillus species screened for lipase and esterase production abilities. Qualitatively, 11 Aspergillus isolates showed lipase and/or esterase activities and only 4 isolates were able to perform WFO transesterification under the tested conditions. Two Aspergillus isolates showed relatively high FAME yields, thus were selected as good enzyme producers. These two isolates were molecularly identified using rRNA gene sequence ITS1 and ITS2 as A. tamarii NDA03a (Genbank Accession Number MK849615) and A. flavus NDA04a (Genbank Accession Number MK811208), respectively. These identified isolates were exposed to ethyl methanesulfonate (EMS) for producing hyper lipolysis mutants. Mutagenesis led to 13.15 and 14.45% improvement of the WFO transesterification by A. tamarii NDA03a and A. flavus NDA04a, respectively. Random amplified polymorphic DNA (RAPD) analysis of the produced mutants confirmed the genetic basis of the activity variation. Genetic polymorphism reached to 79.31% and 80.65% between A. flavus NDA04a and A. tamarii NDA03a mutants and their corresponding wild types, respectively.