Fermentation of glycerol by Anaerobium acetethylicum and its potential use in biofuel production

• Published in: Microbial biotechnology Vol. 10; no. 1; pp. 203 - 217
• Main Authors: Patil, Yogita, Junghare, Madan, Müller, Nicolai
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.01.2017; Wiley-Blackwell; John Wiley and Sons Inc
• Subjects: Acetates - metabolism; Acetic acid; Alternative energy sources; Bacteria; BASIC BIOLOGICAL SCIENCES; Biodiesel fuels; Biofuels; Biomass; Biotechnology & Applied Microbiology; Clostridiales - growth & development; Clostridiales - metabolism; Diesel; Ethanol; Ethanol - metabolism; Experiments; Fermentation; Formates - metabolism; Fuels; Genomes; Glyceraldehyde; Glycerol; Glycerol - metabolism; Glycolysis; Growth rate; Heat conductivity; Hydrogen; Hydrogen - metabolism; Metabolic Networks and Pathways; Microbiology; Microorganisms; Organic chemistry; Propylene Glycol - metabolism; Proteomes; Sensors; Toxicity; Waste disposal; Yeast; Yeasts; United States > US; Germany
• ISSN: 1751-7915; 1751-7915
• DOI: 10.1111/1751-7915.12484

Summary Growth of biodiesel industries resulted in increased coproduction of crude glycerol which is therefore becoming a waste product instead of a valuable ‘coproduct’. Glycerol can be used for the production of valuable chemicals, e.g. biofuels, to reduce glycerol waste disposal. In this study, a novel bacterial strain is described which converts glycerol mainly to ethanol and hydrogen with very little amounts of acetate, formate and 1,2‐propanediol as coproducts. The bacterium offers certain advantages over previously studied glycerol‐fermenting microorganisms. Anaerobium acetethylicum during growth with glycerol produces very little side products and grows in the presence of maximum glycerol concentrations up to 1500 mM and in the complete absence of complex organic supplements such as yeast extract or tryptone. The highest observed growth rate of 0.116 h−1 is similar to that of other glycerol degraders, and the maximum concentration of ethanol that can be tolerated was found to be about 60 mM (2.8 g l−1) and further growth was likely inhibited due to ethanol toxicity. Proteome analysis as well as enzyme assays performed in cell‐free extracts demonstrated that glycerol is degraded via glyceraldehyde‐3‐phosphate, which is further metabolized through the lower part of glycolysis leading to formation of mainly ethanol and hydrogen. In conclusion, fermentation of glycerol to ethanol and hydrogen by this bacterium represents a remarkable option to add value to the biodiesel industries by utilization of surplus glycerol. A novel bacterial strain ferments glycerol almost exclusively to ethanol and hydrogen. The maximum glycerol concentration tolerable for growth is 1.5 M (138 g/l) and no complex organic growth supplements are required. Ethanol accumulates in growth media up to a concentration of about 60 mM (2.8 g/l).