Fermentative hydrogen production by Clostridium butyricum CGS5 using carbohydrate-rich microalgal biomass as feedstock

Fermentative hydrogen production using sorghum husk as a biomass feedstock and process optimization

“…Thus, higher utilization of all sugars present in SH hydrolysates and lower soluble metabolites production in the pH-control approach (initial pH 6.5 followed by pHcontrol at 5.5) may contribute to the increase in H 2 production and production rate. Our results are consistent with those reported with C. butyricum CGS5 using carbohydrate-rich Chlorella vulgaris hydrolysates [20] and C. beijerinckii KCTC 1785 using food waste [21], where maintaining pH at 5.5 exhibited maximum H 2 production and production rate. In the present study, the maximum H 2 production and H 2 yield obtained under the optimal conditions is found to be better or comparable to most of the reported results from relevant studies suggesting that SH hydrolysates can be used as fermentation media for H 2 production ( Table 1).…”

“…The low yield of H 2 at higher SH hydrolysate concentration could also be due to the generation of chemical inhibitors including terpenes and furfural derivatives which may be present in small quantity [31,32]. Similar observations were obtained in various H 2 production studies including Clostridium butyricum [34], Clostridium beijerinckii RZF-1108 [35], Clostridium saccharoperbutylacetonicum N1-4 [38], and Clostridium butyricum CGS5 [20], where increasing the substrate concentration beyond a certain level inhibited the fermentation process. We supposed that for efficient conversion of SH hydrolysate into H 2 is possible by using molecular biology tools to modify the strain for the conversion of xylose and arabinose into H 2 and also need detoxification of hydrolysates to remove the toxic compounds may present in small quantity.…”

“…The composition and concentration of substrate is also an important factor affecting the kinetics of biohydrogen production [20,34,36]. In the present investigation, the effect of the concentration of acid-pretreated (0.2%) SH hydrolysate (2.5 ~ 10.0 g RS/L) on biohydrogen production was determined (Fig.…”

“…The presence of acidogenic soluble metabolites decreased the pH (6.5 ~ 2.0) of the fermentation media. At the end of the fermentation, dominant ethanol production was observed, which is unfavorable to biohydrogen production [20,33]. These results suggest that biohydrogen production efficiency is influenced not only by the initial sugar concentration but also by the soluble metabolites generated during fermentation.…”

“…have been found to be very efficient dark-fermentative microorganisms [17,18]. Recent studies for dark fermentative biohydrogen production using cellulosic biomass suggested that conditions for cellulose degradation and dark H 2 fermentation are quite different, and these microorganisms are inefficient utilizers of cellulose in producing H 2 in one stage H 2 production process [19,20]. Therefore, a two-step separate hydrolysis and fermentation (SHF) process has been applied in which cellulose hydrolysis is carried out in the first stage and the hydrolysate is efficiently converted into H 2 in the second stage [9,17].…”