Comparative study between compost and granular sludge inoculums as promising microbial consortia sources for biohydrogen production from food industry wastewater

Abstract

This study performed a comparative analysis of anaerobic microbial communities from compost or granular sludge inoculum over the course of industrial substrate codigestion in order to identify the range of carbon-nitrogen ratios (20 to 50) that increase the biohydrogen production. The batch bioreactors were operated at pH = 5.5 ± 0.3 and 35 °C. Physicochemical characterization showed a pH < 4.0 after 32 h; a gradual decrease in organic matter was observed, reaching a maximum of 90% recovery. The highest biohydrogen yield was 72.9 ± 5.7 mL H2 g−1CODrem, which occurred after conducting fermentation with compost inoculum at a carbon–nitrogen ratio of 35. These fermentation processes were characterized by the proliferation of native populations from the substrate (Lactobacillus and Lactococcus) and the intrinsic inoculum conditions (Citrobacter spp. and Megasphaera elsdenii). A shift in the dominant biohydrogen-producing microbial population over time was observed mainly for reaction systems with high biohydrogen yields. Citrobacter spp., Kluyvera cryocrescens, and Rahnella spp. all proliferated during the codigestion processes facilitated by the compost inoculum samples, while Megasphaera elsdenii performed a similar function in the granular sludge inoculum bioreactors.