Exploring the potential of Bacillus licheniformis AP1 for fermentive biohydrogen production using starch substrate: BBD based process parameter optimization

Abstract

Performance of Bacillus licheniformis AP1 was first time examined for hydrogen production using starch substrate. The current study enhanced hydrogen yield by exploring the bacterium for various nutritional and environmental factors. The impact of three key variables such as pH (4.5, 5.5, 6.5 and 7.5), iron sulphate (0.01 mg/L, 0.05 mg/L, 0.25 mg/L, 1.25 g/L, 6.25 mg/L), and nickel chloride (0.0875 mg/L, 0.175 mg/L, 0.2 mg/L, 0.7 mg/L, 1.25 mg/L, 1.75 mg/L) were searched to study and analyze their individual effect on hydrogen production and yield. Primary optimization (by one factor at a time) of these factors gave us a range of optimal values which was further processed for multiple parameters optimization. A Box-Behnken Design (BBD) for three variables was used to attain the maximum yield of hydrogen production by using the optimized values of each variable. The interactive parameters were set as runs (from 1 run to 15 run) in each batch system using response surface methodology (RSM) by SYSTAT-12. The predicted optimized values were obtained as 6.247 (pH), 0.268 mg/L (iron sulphate), and 0.439 mg/L (nickel concentration) with maximum cumulative biohydrogen production 3.2 L H2/L from statistical analysis. Experimental validation of the optimized setpoints produced maximum cumulative hydrogen production of 2.77 L/L medium (highly close to the predicted response i.e. 3.2 L H2/L) with a maximum yield of 3.85 mol H2/mol sugar. At the predicted optimized condition, a batch test was performed using rice water as substrate which produced maximum output 3.2 mol H2/ mol sugar.