Problem statement: One of the main factors influenced the bacterial productivity and total yield of hydrogen is the nitrogen source and its concentration. Approach: Using different nitrogen source with different concentration on bacterial productivity of hydrogen showed to affect on both bacterial productivity of hydrogen and biomass concentration.

The objective of this study is to investigate the effect of salts addition to fermentation medium on hydrogen production, under anaerobic batch culture system. In this study, batch experiments were conducted to investigate the inhibitory effect of both NaCl and sodium acetate on hydrogen production. The optimum pH and temperature for hydrogen production were at initial pH of 7.0 and 30 degrees C. Enhanced production of hydrogen, using glucose as substrate was achieved. In the absence of Sodium Chloride and Sodium Acetate enhanced hydrogen yield (Y(P/S)) from 350 mL g(-1) glucose utilized to 391 mL g(-1) glucose utilized with maximum hydrogen productivity of 77.5 ml/L/h. Results also show that sodium chloride and sodium acetate in the medium adversely affect growth. Hydrogen yield per biomass (Y(P/X)) of 254 ml/L/g, biomass per substrate utilized (Y(X/S)) of 0.268 and (Y(H2/S) of 0.0349. The results suggested that Sodium at any concentration resulted to inhibit the bacterial productivity of hydrogen.

The aim of this study was to investigate the influence of some environmental factors on bacterial metabolism. Fermentative hydrogen production by C. acetobutylicum, using glucose as the substrate. The effect of initial pH (4-8), inoculum size (1-20% (v/v)) and glucose concentration (1-30 g L(-1)) on hydrogen production were studied. The optimum cultivation temperature for hydrogen production was at 30 degrees C. The results show that substrate concentration and inoculum size resulted in hydrogen yield (Y(P/S)) of 391 mL g(-1) glucose utilized with maximum hydrogen productivity of 77.5 mL/L/h. Higher substrate concentration or inoculum size adversely affects hydrogen production, which decreases hydrogen yield by 15% to 334 mL g(-1) glucose utilized when 30% (v/v) inoculum size was used. The use of 30 g L(-1) substrate concentration resulted in a 75% decrease to 97 mL g(-1) glucose supplied. Concluded that proper Xo/So enhanced the hydrogen production.

Problem statement: Some component of fermentation medium showed to reduce the bacterial production of hydrogen. Approach: Reinforced clostridium medium is a selected medium for Clostridium species. Reformulation this medium regarding hydrogen production may focus on such medium composition that enhance or reduce the bacterial productivity. The optimum pH and temperature for hydrogen production were at initial pH of 7.0 and 30ºC. Results: The results show that both nitrogen source and its concentration affected biomass growth as well as H 2 yield. Yeast extract at concentration of 13 gL −1 was the best organic nitrogen source and resulted in hydrogen yield (Y P/S) of 308 mL g −1 glucose utilized with biomass concentration of 1.1 gL −1 , hydrogen yield per biomass (Y P/X) of 280 mL g −1 L −1 , biomass per substrate utilized (Y X/S) of 0.22 and produced hydrogen in gram per gram of glucose utilized (Y H2/S) of 0.0275. C/N of 70 enhanced the Y P/S from 308 mL g −1 to 350 mL g −1 glucose utilized with biomass concentration of 1.22 gL −1 , Y P/X of 287 mL g −1 L −1 , Y X/S of 0.244 and (Y H2/S) of 0.03125. In the absence of sodium chloride and sodium acetate further enhanced Y P/S from 350 mL g −1 glucose utilized to 391 mL g −1 glucose utilized with maximum hydrogen productivity of 77.5 mL L −1 h −1 , whereas RCM medium gave the highest hydrogen productivity of 63.5 mL L −1 h −1. Results also show that Sodium Chloride and Sodium Acetate in the medium adversely affect growth. Removal of both components from the medium enhanced the biomass concentration from 1.22-1.34 gL −1 , Y P/X of 254 mL g −1 L −1 , Y X/S of 0.268 and (Y H2/S) of 0.0349. Conclusion: The medium an improved containing (glucose 5 gL −1 , Yeast extract gL −1 , L-Cystine. HCl 1 gL −1 and Bacteriological agar 0.5 gL −1), was able to enhance the hydrogen productivity.

This study was carried out to study the effect of trace metal addition for hydrogen production The results show that this bacterial need a selected nutrient with selected concentration. The optimum parameters for cultivation were at initial pH of 7.0 and temperature of 30°C. Trace metal addition to the new medium showed that only iron enhanced the H 2 yield. The results showed that 25 mgL −1 FeSO 4 ⋅7H 2 O enhanced the hydrogen yield from 391 mLg −1 to 408 mLg −1 glucose utilized with biomass concentration of 1.38 gL

The effect of removal of resultant gas resulted in enhancement of the H2 yield. The technique of CO2 scavenging resulted in H2 yield being improved from 408 mL g(-1) to reach the maximum of 422 mL g'. The highest hydrogen productivity of 87.9 ml L(-1) h(-1) was obtained by CO2 scavenging. Biomass concentration was enhanced to 1.47 g L(-1), Y(P,X) of 287 ml g(-1) L(-1), Y(X/S) of 0.294 and Y(H2/s) of 0.0377 by the use of CO2 scavenging. The results suggested that the presence of the gaseous products in fermentation medium and headspace adversely effect biomass growth and hydrogen production.