Syngas fermentation for hydrogen and volatile fatty acids production: Effect of inoculum source, pretreatment, and environmental parameters using natural microbial consortia

This study evaluates the biological water-gas shift reaction of syngas into hydrogen (H 2 ) using natural microbial consortia from wastewater treatment facilities. Various inoculum pretreatment techniques to inhibit methanogenesis and different operational conditions such as temperature, pH, and inoculum concentrations were tested to improve H 2 production. An inoculum heat pretreatment of 85 °C for 30 min followed by a fermentation temperature of 65 °C and an initial pH value of 9, resulted in the maximum CO-to-H 2 conversion (2.35 ± 0.00 mmol) in which Firmicutes dominated with a total inhibition of methanogens, such as with the chemical inhibition treatment. Additionally, volatile fatty acids (VFA) production was observed, being influenced by the pre-treatment. This study highlights the potential of natural consortia for efficient, cost-effective and scalable syngas fermentation processes, offering new insights into the bioconversion of H 2 without costly chemical inhibitors. • Thermophilic temperatures were efficient for the reaction by natural consortia. • The highest H 2 conversion free of CH 4 was at 65 °C and pH 9. • The improved heat pretreatment was as efficient as the chemical pretreatment. • Microbial genera were distinct between pretreatments to inhibit methanogens.