Optimisation and Comparative Evaluation of Fermentative Hydrogen Production using Pure and Co-culture of Clostridium beijerinckii and Enterobacter aerogenes

Abstract

Hydrogen, the only fuel to produce water as a by-product is seen as an ideal fuel for the future that can be produced from waste feedstock. The use of optimum bioreactor conditions and co-cultures with well-defined strains offer great potential to enhance hydrogen production due to diverse metabolic pathways. This study was aimed at determining the optimum pH and temperature on hydrogen production rate by Clostridium beijerinckii 6444 using glucose as substrate as well as investigating the influence of co-culture comprising of C. beijerinckii 6444 and Enterobacter aerogenes NCIMB 10102 on rate of hydrogen production and yield from glucose, molasses, crude glycerol and seed cake via dark fermentation. Batch fermentation in serum bottles was carried out in order to determine the total accumulative hydrogen gas, biomass concentration, and feedstock consumption in four days of fermentation. The co-culture was further scaled up to a 5 L fermenter. The optimum pH and temperature corresponding to 6.2 and 30 ^oC respectively were determined. The co-culture recorded the highest cumulative hydrogen volume (66.5 ± 4.2 ml) from crude glycerol though it did not significantly increase the yields. The decrease in hydrogen production was observed as a result of formation of volatile fatty acids (acetic acid 1.5-3.1 g/l, butyric acid 3.2-5.6 g/l) among others which have inhibitory effects. The highest dead cell count of 3.4 x 10⁸ cells/ml indicated that pH was inhibitory. The scale-up showed an increase in the hydrogen production rate from 13.38 ml/l/hr to 24.13 ml/l/hr and yield of 1.37 mol H₂/mol glycerol after 24 hrs. The study showed that the co-culture of C. beijerinckii and E. aerogenes can be used to enhance hydrogen production from crude glycerol as a cheap carbon source.