Biosynthesis of Ethanol and Hydrogen by Glycerol Fermentation Using <i>Escherichia coli</i>

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.

An Overview of Recent Research in the Conversion of Glycerol into Biofuels, Fuel Additives and other Bio-Based Chemicals

“…The fermentation of glycerol using Escherichia coli K12 also revealed that a maximum ethanol yield of 0.40 g/g glycerol was obtained when 10 g/L concentration of glycerol was used under membrane headspace conditions [88]. Similarly, Loaces et al [95] used E. coli to improve ethanol production and glycerol conversion using heterologous genes (metagenomic fragment) obtained from anaerobic purge sludge.…”

“…The use of microorganisms to produce hydrogen has also been studied and reported over the years, and findings have shown enhanced crude glycerol utilization without undergoing the high cost of the purification process associated with having pure glycerol. The use of Enterobacter spH1, Enterobacter spH2 and Citrobacter freundii H3 [87], Escherichia coli K12 [88], Clostridium freundii H3 [89], Klebsiella pneumonia TR 17 [90], Thermotoga maritime and Thermotoga neapolitana [91] have shown relatively large quantities of H 2 (>70%) under varying conditions. However, the details of microbial hydrogen production are beyond the scope of this review.…”

Alkali and glycerol pretreatment of West African biomass for production of sugars and ethanol

“…Glycerol is a by-product of biodiesel production, produced in large quantities and discarded as waste in Africa. However, glycerol can be converted directly to ethanol (Chaudhary et al, 2011) or applied as organic co-solvent in biomass pretreatment (Lynam and Coronella, 2014). Though majority of glycerol pretreatment studies have focused on elevated temperatures (170-400 o C) (Martin et al, 2015;Martín et al, 2011;Romani et al, 2013), their applications at moderate temperatures have not been given much attention.…”

Mini review: hydrogen and ethanol co-production from waste materials via microbial fermentation

“…Many facultative anaerobes are able to co-produce hydrogen and ethanol, such as Klebsiella sp. (Wu et al 2011), Enterobacter aerogenes (Ito et al 2005;Jitrwung and Yargeau 2011;Reungsang et al 2013;Sakai and Yagishita 2007) and Escherichia coli (Chaudhary et al 2011;Hu and Wood 2010;Murarka et al 2008;Yoshida et al 2006). Examples of the utilization of facultative anaerobes in hydrogen and ethanol fermentation are provided in Table 1.…”