Application of a novel biological-nanoparticle pretreatment to Oscillatoria acuminata biomass and coculture dark fermentation for improving hydrogen production

BACKGROUND: Energy is the basis and assurance for a world's stable development; however, as traditional non-renewable energy sources deplete, the development and study of renewable clean energy have emerged. Using microalgae as a carbon source for anaerobic bacteria to generate biohydrogen is a clean energy generation system that both local and global peers see as promising. RESULTS: Klebsiella pneumonia, Enterobacter cloacae, and their coculture were used to synthesize biohydrogen using Oscillatoria acuminata biomass via dark fermentation. The total carbohydrate content in O. acuminata was 237.39 mg/L. To enhance the content of fermentable reducing sugars, thermochemical, biological, and biological with magnesium zinc ferrite nanoparticles (Mg-Zn Fe(2)O(4)-NPs) pretreatments were applied. Crude hydrolytic enzymes extracted from Trichoderma harzianum of biological pretreatment were enhanced by Mg-Zn Fe(2)O(4)-NPs and significantly increased reducing sugars (230.48 mg/g) four times than thermochemical pretreatment (45.34 mg/g). K. pneumonia demonstrated a greater accumulated hydrogen level (1022 mLH(2)/L) than E. cloacae (813 mLH(2)/L), while their coculture showed superior results (1520 mLH(2)/L) and shortened the production time to 48 h instead of 72 h in single culture pretreatments. Biological pretreatment + Mg-Zn Fe(2)O(4) NPs using coculture significantly stimulated hydrogen yield (3254 mLH(2)/L), hydrogen efficiency)216.9 mL H(2)/g reducing sugar( and hydrogen production rate (67.7 mL/L/h) to the maximum among all pretreatments. CONCLUSION: These results confirm the effectiveness of biological treatments + Mg-Zn Fe(2)O(4)-NPs and coculture dark fermentation in upregulating biohydrogen production. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12934-023-02036-y.