Carbon source utilization and hydrogen production by isolated anaerobic bacteria

Abstract

Five bacterial isolates were tested for their ability to generate hydrogen during anaerobic fermentation with various carbon sources. One isolate from sheep rumen was identified as Escherichia coli and four isolates belonged to Clostridium spp. Glucose, arabinose, ribose, xylose, lactose and cellobiose were used as carbon sources. Results showed that all bacterial strains could utilize these compounds, although the utilization of pentoses diminished growth yield. The excretion of monocarboxylic acids (acetate, propionate, formiate, butyrate) into medium was changed after replacing glucose by other carbon sources. Di- and tricarboxylic acids were excreted in negligible amounts only. Spectra of excreted carboxylic acids were unique for each strain and all carbon sources. All isolates produced H2 between 4—9 mmol·L−1 during the stationary phase of growth with glucose as energy source. This value was dramatically reduced when pentoses were used as carbon source. Lactose and cellobiose, starch and cellulose were suitable substrates for the H2 production in some but not all isolates. No H2 was produced by proteinaceous substrate, such as blood. Results show that both substrate utilization and physiological responses (growth, excretion of carboxylates, H2 production) are unique functions of each isolate.

Characterisation of Cellulolytic Bacteria Isolated from Agricultural Soil in Central Lithuania

“…In environmental conditions, microorganisms' survival can be predicted by the capability to utilise a range of available carbohydrates as carbon and energy sources [65]. The efficient uptake rate of glucose agrees with the results of Jame et al, which showed that all investigated bacterial isolates utilised this monosaccharide as a carbon source [66]. Due to the fact that glucose is the preferable sugar, most presumably because it can enter glycolysis directly, whereas other sugars need to be enzymatically transformed.…”

Biochemical Hydrogen Potential Tests Using Different Inocula

“…spores was studied, since previous works found Clostridium perfringens sp. to be the most dominant hydrogen producing culture [23][24][25][26][27]. The concentration was observed to vary by a factor of up to 12, ranging from a maximum of 150 CFU/mg found for the activated sludge sample (IN1) to a minimum of 13 CFU/mg (IN2).…”

“…Several works found Clostridium perfringens sp. to be the most dominant hydrogen producing culture [23][24][25][26][27], and it is widely adopted when evaluating hydrogen production from a pure culture [24,28]. Spores were measured because Clostridium sp.…”

“…Several studies use pure hydrogen producing cultures such as Clostridium sp. to avoid the presence of HCB [23][24][25][26][27][28][29]. Nevertheless, since in full scale digesters bacteria coexist in a wide range of species, and the fermentation of substrates into biohydrogen involves a wide consortium of microorganisms [30], the use of mixed cultures belonging to operative facilities is preferred by most authors [6,11,[13][14][15][16][17][18][19][20][21][31][32][33].…”