Evaluation of Biohydrogen Production from Co-fermentation of Carbohydrates and Proteins

Emmanuel Andrew Tepari Jr,, The University of Western Ontario

Abstract

The aim of this study was to examine volatile fatty acid (VFA) production from a proteinaceous substrate, bovine serum albumin (BSA) for a pH range of 5 – 9, and to further assess its impact on hydrogen production in a co-fermentation process using starch and BSA at different ratios. The established optimum conditions for VFA production from BSA were an initial pH of 8, incubation time of 3 days and an operating temperature of 37 ℃. Using these fermentation conditions, the stoichiometric reactions that describe the anaerobic degradation of BSA were investigated. A methodology that describes organic acid production from BSA by using a single stoichiometric reaction was developed. With the amino acid content of BSA and by selecting the dominant amino acid fermentation reaction pathways, it was feasible to determine the stoichiometric coefficients of the dominant VFA in the single reaction step. Hydrogen production from the co-fermentation of starch and BSA in batch system was studied for five different ratios (C1 – C5). The co-fermentation process had a synergistic impact on hydrogen production and the optimum ratio occurred at C4 (80% starch + 20% BSA) with a hydrogen yield of 350 mLH₂/gCOD_added which was 38% higher than the expected. MINITAB-16 was used for data analysis, 3D contour diagrams and response (VFA, ammonia, and hydrogen) optimizations for C4 (80% starch + 20% BSA) were developed. The regression analysis of the responses adequately followed second-order polynomial models. The optimum concentration range for VFA and ammonia at which pH control was not necessary obtained from the Box-Behnken design were respectively 125 – 133 mg/L and 41 – 47 mg/L. Thus, the fermentative hydrogen production process would be feasible without pH control at a carbohydrate-to-protein COD ratio of 4:1.