Hydrogen production by sequential dark and photofermentation using wet biomass hydrolysate of Spirulina platensis: Response surface methodological approach

Microalgae and cyanobacteria can be used as a potential biomass to produce hydrogen from stored glycogen and starch through fermentation and photofermentation. In this study, the potential of algal biomass i.e. Spirulina platensis hydrolysate as a substrate for sequential fermentative (I-stage) and photo-fermentative (II-stage) biohydrogen production was evaluated. Response Surface Methodology (RSM) was employed to find the optimum photofermentation conditions. From the preliminary optimization experiments, it was found that the significantly affecting factors for H-2 production were pH, dilution fold (D.F.) of fermentate and Fe(II) sulfate concentration during photofermentation (second stage). In the present study, 1% (w/v) Spirulina platensis hydrolyzate produced 23.06 +/- 3.63 mmol of H-2 with yield of 1.92 +/- 0.20 mmol H-2/g COD reduced. In the second stage experiment 1510 +/- 35 mL/l hydrogen was produced using inoculum volume-20.0% (v/v) and inoculum age-48 h of co-culture of Rhodobacter sphaeroides NMBL-01 and Bacillus firmus NMBL-03 under conditions pH-5.95, D.F. of dark fermentate-20.30 folds, Fe(II) sulfate concentration 0.412 mM, temperature-32 +/- 2 degrees C and light intensity-2.5 klux. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

In this study, the potential of Spirulina platensis hydrolysate as a substrate for biohydrogen production through sequential fermentative and photofermentative processes was evaluated. Response Surface Methodology was used to determine the optimal photofermentation conditions. The experiments showed that factors such as pH, dilution fold of fermentate, and Fe(II) sulfate concentration significantly affected hydrogen production, with promising results obtained under specific conditions in the second stage experiment.