Semi-pilot scale production of biodiesel from waste frying oil by genetically improved fungal lipases.

This paper addresses the issue of combining the usage of waste frying oil (WFO), as a feedstock, and a lipase produced in solid-state fermentation (SSF), as a biocatalyst, for semi-pilot scale production of biodiesel as fatty acid methyl esters (FAME). Two fungal mutants namely; Rhizopus stolonifer 1aNRC11 mutant F (1F) and Aspergillus tamarii NDA03a mutant G (3G) were used as a cocatalyst. The two mutants were cultivated separately by SSF in a tray bioreactor. The dried fermented solid of 1F and 3G mutants were used in a ratio of 3:1, respectively, for WFO transesterification. Optimization of several semi-pilot process stages including SSF and WFO transesterification reaction conditions resulted in 92.3% conversion of WFO to FAME. This FAME yield was obtained after 48 h using 10% cocatalyst (w/w of WFO), 10% water (w/w of WFO) and 3:1 methanol/ WFO molar ratio at 30 °C and 250 rpm. A preliminary economic evaluation of produced biodiesel price (190 $/Ton) is less than half the price of petroleum diesel in Egypt (401$/Ton) and is about 40.3% the price of biodiesel produced using a pure enzyme, which is a promising result. This strategy makes the biodiesel synthesis process greener, economical and sustainable.