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Open Access Highly Accessed Original article

Optimization of cultural conditions for conversion of glycerol to ethanol by Enterobacter aerogenes S012

Raymond E S Nwachukwu1*, Abolghasem Shahbazi2, Lijun Wang2, Mulumebet Worku3, Salam Ibrahim4 and Keith Schimmel1

Author Affiliations

1 Energy and Environmental Systems, Sockwell Hall North Carolina A&T State University, 1601 East Market Street, Greensboro, NC, 27411, USA

2 Biological Engineering, North Carolina Asss&T State University, Greensboro, NC, USA

3 Department of Animal Sciences, North Carolina A&T State University, Greensboro, NC, USA

4 Food and Nutritional Sciences, North Carolina A&T State University, Greensboro, NC, USA

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AMB Express 2013, 3:12  doi:10.1186/2191-0855-3-12

Published: 6 February 2013

Abstract

The aim of this research is to optimize the cultural conditions for the conversion of glycerol to ethanol by Enterobacter aerogenes S012. Taguchi method was used to screen the cultural conditions based on their signal to noise ratio (SN). Temperature (°C), agitation speed (rpm) and time (h) were found to have the highest influence on both glycerol utilization and ethanol production by the organism while pH had the lowest. Full factorial design, statistical analysis, and regression model equation were used to optimize the selected cultural parameters for maximum ethanol production. The result showed that fermentation at 38°C and 200 rpm for 48 h would be ideal for the bacteria to produce maximum amount of ethanol from glycerol. At these optimum conditions, ethanol production, yield and productivity were 25.4 g/l, 0.53 g/l/h, and 1.12 mol/mol-glycerol, repectively. Ethanol production increased to 26.5 g/l while yield and productivity decreased to 1.04 mol/mol-glycerol and 0.37 g/l/h, respectively, after 72 h. Analysis of the fermentation products was performed using HPLC, while anaerobic condition was created by purging the fermentation vessel with nitrogen gas.

Keywords:
Enterobacter aerogenes; Ethanol; Glycerol; Metabolic pathway; Fermentation