Fermentative hydrogen and polyhydroxybutyrate production from pretreated cyanobacterial blooms

The cell wall and cytoplasmic membrane components of algal biomass (in cyanobacterial blooms) are resistant to biodegradation during anaerobic digestion. Various pretreatment methods including thermal, alkaline and acid pretreatments, were performed (each as a two-stage process) to increase the biodegradability of the algal biomass in terms of hydrogen and polyhydroxybutyrate (PHB) production. Among the pretreatment methods, thermal pretreatment achieved the highest hydrogen production (113 mL/g VS), followed by alkaline pretreatment (94 mL/g VS). Following hydrogen production, phototrophic bacteria were inoculated into the fermentative broth, for PHB production. The group that had undergone alkaline pretreatment produced the highest amount of PHB (about 1.69 g/L). Our studies indicate that pretreatment is a feasible option for transforming algal biomass into a bio-available material, for the purpose of microbial hydrogen production and PHB conversion.