Biohydrogen production by locally isolated facultative bacterial species using the biomass of Eichhornia crassipes: effect of acid and alkali treatment

Hydrogen (H 2 ) produced from biological methods is a potential option to meet the growing clean energy needs. The present study aimed to produce biohydrogen by dark fermentation from nuisance aquatic weed, Eichhornia crassipes, using facultative anaerobic bacteria. A total of 12 bacterial strains were isolated from different wastewater sources and were screened for the potential of H 2 production using glucose as carbon source. Ten strains showed the H 2 -producing potential and were identified up to the generic level by biochemical tests. Two strains with higher H 2 production were sequenced using PCR technique and identified as Proteus mirabilis and Pseudomonas aeruginosa and selected for the studies with E. crassipes as the substrate. It was found that P. aeruginosa could produce 19.54 ± 0.03% of H 2 from 2% acid (H 2 SO 4 ) treated substrate which was comparatively higher than that of 4 and 8% treatments. P. mirabilis also yielded better results of 5.42 ± 0.02% H 2 f or 2% acid (H 2 SO 4 ) treated substrate than 4 and 8% treatments. In total, 33.52 ± 0.04% of H 2 was produced by P. aeruginosa for the substrate treated with 2% alkali (NaOH). It was noted that with respect to P. mirabilis 4% alkali treated substrate yielded a higher percentage of H 2 (20.23 ± 0.03%) compared to the other two concentrations. The results indicate that alkali treated substrate produced comparatively higher amount of H 2 than that of acid treated substrates. Regarding efficiency, P. aeruginosa was found to be more competent than P. mirabilis.