Production of Bio-Hydrogen Gas and Other Metabolic Gases by Anaerobic Bacteria Grown on Molasses

Abstract

The study had aimed to characterize the production of hydrogen gases by anaerobic bacteria. One isolate was found in sheep ruminal fluid and four isolates were obtained from the activated sludge. These isolates were identified by microscopic methods and by rRNA sequences. One ruminal bacterium was identified as Escherichia coli, and it was found that these isolates from activated sludge were related to Clostridium botulinum, C. perfringens and C. difficile. One strain could not be assigned to any species but was similar to C. botulinum. Growth and production of the metabolic gases with molasses as sole carbon source were measured during the anaerobic cultivation by Micro-Oxymax (Columbus Instruments, Columbus, OH, U.S.A.) gas analyzer. One of the most available saccharidic waste products is molasses. The growth on molasses as carbon source was done to test the production of H 2 . It was found that all tested Clostridium isolates (AK 1-4, AK 1-5, AK 1-9 and AK 1-12) and E. coli isolate (No 2-24) had utilized molasses as carbon source monitored by production of CO 2 gas. All these strains produced H 2 gas, and CO gas in concentration range 102 µmol L -1 , and H 2 S gas in concentrations lower by one order of magnitude. Kinetics of evolution of these gases was different suggesting that they are produced by independent processes. Results show that metabolic gases are produced mainly in the exponential phase of growth.