Effect of Media Composition on Biohydrogen Production from Fig (<i>Ficus carica</i>) by Dark Fermentation

Abstract

In this study, mesophilic batch fermentation experiments were conducted to investigate the effects of varying C/N ratios (25 -100) on  biohydrogen production. The fermentable sugar was obtained from microwave hydrolyzed waste fig (Ficus carica). A control experiment  without external nitrogen addition was also set-up to evaluate if the nitrogen content of hydrolyzed fig could sustain biohydrogen production. The highest cumulative hydrogen volume (861± 0.5 ml) and volumetric production (4.3 ± 0.3 L/L_reactor) were obtained at C/ N=50. The yields varied between 0.9 ± 0.21 and 1.1 ± 0.23 mol H2 mol-1 T_Sconsumed for C/N= 25-100. The highest production rates achieved  were 11.5 ± 0.12 ml h-1 and 57.5 ± 0.14 ml L^-1 h ^-1 at C/N=50. Thus, the best ratio in terms of substrate conversion to hydrogen  is C/N=50 which can be evaluated as the nitrogen-sufficient condition. The nitrogen content of the hydrolyzed waste fig (control) was not  sufficient for efficient biohydrogen production and external nitrogen addition is required to obtain a higher production rate. There were  significant differences between the C/N ratio for cumulative hydrogen volumes, hydrogen production rate and volumetric hydrogen  production rate.