Biosynthesis of Ethanol and Hydrogen by Glycerol Fermentation Using &amp;lt;i&amp;gt;Escherichia coli&amp;lt;/i&amp;gt;

Nida Chaudhary,Lamin S Kassama,Benjamin K Simpson,Michael O Ngadi

doi:10.4236/aces.2011.13014

Biosynthesis of Ethanol and Hydrogen by Glycerol Fermentation Using &lt;i&gt;Escherichia coli&lt;/i&gt;

Nida Chaudhary, Lamin S Kassama + Show 2 more

Open Access

https://doi.org/10.4236/aces.2011.13014

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Abstract

Production of high value products from glycerol via anaerobic fermentation is of utmost importance for the biodiesel industry. The microorganism Escherichia coli (E. coli) K12 was used for fermentation of glycerol. The effects of glycerol concentration and headspace conditions on the cell growth, ethanol and hydrogen production were investigated. A full factorial experimental design with 3 replicates was conducted in order to test these factors. Under the three headspace conditions tested, the increase of glycerol concentration accelerated glycerol fermentation. The yields of hydrogen and ethanol were the lowest when glycerol concentration of 10 g/L was used. The maximum production of hydrogen was observed with an initial glycerol concentration of 25 g/L at a final concentration of hydrogen was 32.15 mmol/L. This study demonstrated that hydrogen production negatively affects cell growth. Maximum ethanol yield was obtained with a glycerol concentration of 10 g/L and was up to 0.40 g/g glycerol under membrane condition headspace. Statistical optimization showed that optimal conditions for hydrogen production are 20 g/L initial glycerol with initial sparging of the reactor headspace. The optimal conditions for ethanol production are 10 g/L initial glycerol with membrane.

Highlights

The continuous use of fossil fuels is globally accepted as not sustainable largely because of the underlying environmental factors
This work evaluated the effect of glycerol concentration, argon sparging and the use of silicon rubber membrane in lab-scale bioreactor using E. coli for glycerol fermentation and ethanol and H2 production
The highest ethanol yield was obtained with continuous sparging in the headspace and 10 g/L initial glycerol concentration and was up to 0.38 g/g

Summary

Introduction

The continuous use of fossil fuels is globally accepted as not sustainable largely because of the underlying environmental factors. Schenk et al [1] reported that the greenhouse gasses in the environment have already exceeded “dangerously higher” threshold of 450 ppm CO2-e. These starling findings are leading governments to establish regulations to reduce CO2 emissions. Yazdani [2] reported that 10 lb of crude glycerol is generated for every 100 lb of biodiesel fuel produced by transesterification of vegetable oils or animal facts. Glycerol becomes a waste stream instead of being a desirable co-product of significant economic value [2] and in compliance to environmental regulation the burden of cost for disposal of the effluent became a liability for plants [4]. Improving the bioconversion methods of the low-cost glycerol into higher valued product will provide an incentive for the commercialization of glycerol into biofuel

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