Fermentative bio-hydrogen production of food waste in the presence of different concentrations of salt (Na ⁺ ) and nitrogen

Fermentation of food waste in the presence of different concentrations of salt (Na ⁺ ) and ammonia was conducted to investigate the interrelation of Na ⁺ and ammonia content in biohydrogen production. Analysis of the experimental results showed that peak hydrogen production differed according to the ammonia and Na ⁺ concentration. The peak hydrogen production levels achieved were (97.60, 91.94, and 49.31) ml/g COD at (291.41, 768.75, and 1,037.89) mg-N/L of ammonia and (600, 1,000, and 4,000) mg-Na ⁺ /L of salt concentration, respectively. At peak hydrogen production, the ammonia concentration increased along with increasing salt concentration in the medium. This means that for peak hydrogen production, the C/N ratio decreased with increasing salt content in the medium. The butyrate/acetate (B/A) ratio was higher in proportion to the bio-hydrogen production (r-square: 0.71, p-value: 0.0006). Different concentrations of Na ⁺ and ammonia in the medium also produced diverse microbial communities. Klebsiella sp., Enterobacter sp., and Clostridium sp. were predominant with high bio-hydrogen production, while Lactococcus sp. was found with low bio-hydrogen production.