Development of ethanol production from cooking oil glycerol waste by mutant Enterobacter aerogenes

Abstract

Bacterial strains, capable of producing ethanol by using cooking oil glycerol waste (derived from biodiesel production) as sole C-source were screened from soil samples. Based on 16S rRNA sequence, the selected strain was identified as Enterobacter aerogenes G2WG. The sequence was submitted to GenBank and the accession number KU315428 was obtained. The genetic nature of the wild type strain was altered for enhancing ethanol production using UV irradiation and chemical method. Three steps of mutation treatment were developed. Finally, the best strain of Enterobacter aerogenes V90M11 was obtained. As E. aerogenes is a facultative anaerobic microbe, it can growth well and produce high yield of ethanol in low aeration condition. At 15 g/l glycerol, E. aerogenase V90M11 converted glycerol waste and pure glycerol into 6.7 and 3.62 g/l ethanol respectively. The highest ethanol (14.77 g/l) was gained from 30 g/l of glycerol waste in batch process at initial pH 8, and 35oC temperature with micro-aeration. It was equivalent to 0.984 mol ethanol/mol glycerol. Fed-batch process was investigated by adding 200 ml (30 g/l glycerol) and 400 ml (55 g/l glycerol) of fresh T-glycerol medium to the culture after 24h fermentation process. It was found that higher ethanol yield of around 33% and 59% was obtained from fed batch than batch process, with initial glycerol of 15 g/l, respectively.

Keywords: Ethanol, cooking oil glycerol waste, Enterobacter aerogenes, mutation, UV, chemical treatment