A review on cyanobacteria cultivation for carbohydrate-based biofuels: Cultivation aspects, polysaccharides accumulation strategies, and biofuels production scenarios

Cyanobacterial biomass has constituted a crucial third and fourth-generation biofuel material, with great potential to synthesize a wide range of metabolites, mainly carbohydrates. Lately, carbohydrate-based biofuels from cyanobacteria, such as bioethanol, biohydrogen, and biobutanol, have attracted attention as a sustainable alternative to petroleum-based products. Cyanobacteria can perform a simple process of saccharification, and extracted carbohydrates can be converted into biofuels with two alternatives; the first one consists of a fermentative process based on bacteria or yeasts, while the second alternative consists of an internal metabolic process of their own in intracellular carbohydrate content, either by the natural or genetic engineered process. This study reviewed carbohydrate-enriched cyanobacterial biomass as feedstock for biofuels. Detailed insights on technical strategies and limitations of cultivation, polysaccharide accumulation strategies for further fermentation process were provided. Advances and challenges in bioethanol, biohydrogen, and biobutanol production by cyanobacteria synthesis and an independent fermentative process are presented. Critical outlook on life-cycle assessment and techno-economical aspects for large-scale application of these technologies were discussed.