Quantitative analysis of the fermentation products of Enterobacter aerogenes.

Abstract

The products of fermentation of many bacteria, including Enterobacter aerogenes, have been determined by earlier methods of analysis. The purpose of this study was to use more modern methods of analysis of fermentation products. E. aerogenes was isolated from soil, and the effect of varied concentration of carbohydrates on hydrogen production by this soil inhabiting bacterium was investigated. The bacterium was grown anaerobically in phenol red broth, supplemented with varied amounts of fermentable carbohydrates (C-4, C-5, C-6 and C-12). Quantitative assays of other major fermentation end products of E. aerogenes, grown on glucose-supplemented medium were also investigated. The technique of high- performance liquid chromatography (HPLC) was used to directly quantitate formic, lactic and acetic acid products. This technique was also used to indirectly quantitate 23- butanedio1 production by E. aerogenes, grown under aeration-agitation, and anaerobic conditions. Carbon dioxide and hydrogen were quantitated by chemical and physical means of analysis respectively. Gas chromatographic analysis established that at the lowest concentration of carbohydrates (0.05 %) the hydrogen content of the gas mixture was at its highest peak, but the quantity of the gas mixture was at lowest level of production. Increasing hydronium ion concentration also resulted in an increase in hydrogen production. A hydrogen to carbon dioxide ratio of 1:4.93 was established. This is similar to the hydrogen to carbon dioxide ratio of 1:5 established by previous investigators. The total quantity of organic acids obtained is comparable to that established by previous methods of analysis, but the quantity of individual species of organic acids differs from the published data. Aeration-agitation resulted in a two fold increase in the production of 2-3-butanediol.