Kinetic Study of Biohydrogen Production Improvement via Dark Fermentation of Sugarcane Molasses by Escherichia marmotae

Abstract

Hydrogen (H2) is expected to become the most sustainable and promising clean alternative fuel in the future. This study evaluated the potential of a new facultative anaerobic bacterium isolated from cow rumen to produce H2 from sugarcane molasses. The bacterial isolate RM122 produced 451.67±12.14 and 387.67 ±19.23 mL/L H2on 6% glucose and 6% molasses sugar, respectively. RM122 was characterized phenotypically, identified genotypically by 16S rRNA sequence analysis as Escherichia marmotae, and deposited in NCBI GenBank database with the accession number OP345936. H2production was improved to 1670.00 ±40.41 mL/L by application of optimization experiments design and kinetic study. Sugarcane molasses was used as a fermentation substrate and the optimum sugar concentration was 4%, The recorded maximum hydrogen production (Hmax) was 560.00±25.98 mL/L with Rmax (maximum hydrogen production rate) of 31.43 ±2.14 mL/L/h, Rmax (MGM)of 30.73 mL/L/h and λ (lag phase) of 15.19 h for 52.43 fermentation time. Hmax of 646.67 ±23.33 mL/L with Rmax(Exp) of 35.28 ±2.65 mL/L/h, Rmax(MGM) of 31.90 mL/L/h, λ of 13.92 h and R2 of 0.9999 were obtained at the optimum pH 8. At the optimum fermentation temperature (35 °C), λ of 4.12 h was achieved to maximize hydrogen production to 828.33 ±21.67 mL/L with Rmax(MGM) of 27.98 mL/L/h, and R2 of 0.9594. At the optimum inoculum size (10%, v/v), the recorded Hmax was 1670.00 ±40.41 mL/L with Rmax (Exp) of 60.00 ±2.04 mL/L/h and λ of 13.50 hrs. These findings suggest using E. marmotae RM122 as a prospective biohydrogen producer from cheap agro-industrial wastes.