Microalgae-based carbohydrates for biofuel production

•Comprehensive knowledge on carbohydrates production from microalgae is provided.•Updates on converting microalgae-based carbohydrates to biofuels is described.•Critical comments on the technical/economic feasibility of the topic are addressed. Microalgae are considered as the most promising renewable feedstock for biofuel production and biorefineries, due to their advantages of fast growth, efficient carbon dioxide fixation, not competing for arable lands and potable water, and potentially accumulating high amounts of lipids and carbohydrates. Since carbohydrates in microalgae biomass are mainly cellulose in the cell wall and starch in the plastids without lignin and low hemicelluloses contents, they can be readily converted into fermentable sugars. However, to date there are very few studies focusing on the use of microalgae-based carbohydrates for biofuel production, which requires more understanding and knowledge to support the technical feasibility of this next-generation feedstock. This review article elucidates comprehensive information on the characteristics and metabolism of main fermentable microalgal carbohydrates (e.g., starch and cellulose), as well as the key factors and challenges that should be addressed during production and saccharification of microalgal carbohydrates. Furthermore, developments on the utilization of microalgae-based feedstock in producing liquid and gaseous biofuels are summarized. The objective of this article is to provide useful knowledge and information with regard to biochemistry, bioprocess engineering, and commercial applications to assist in the viable technology development of for biofuels generation from microalgae-based carbohydrates.