Microalgal biorefinery: Challenge and strategy in bioprocessing of microalgae carbohydrate for fine chemicals and biofuel

Microalgal carbohydrate is one of the major macromolecule metabolites, which has recently gained great attention as an alternative feedstock for wide-range sustainable biobased products. These biopolymers can act as a chemical platform for the production of biofuels through a biochemical conversion process. However, low microalgal carbohydrate productivity at a large-scale production has become a major problem for economical biofuel production. Several strategies have been proposed and the approach only increased carbohydrate content but reduced the microalgal biomass production, resulting in low microalgal carbohydrate productivity. Besides, the inappropriate pretreatments and fermentation approaches specifically with high-energy techniques could cause an increase in the cost of biofuel production. This present review gives a comprehensive discussion on microalgal carbohydrate enhancement strategies via cultivation techniques including the influence of environmental stress on the microalgal biomass and carbohydrate productivity. This paper also reviews the state of art on downstream processing of microalgal biomass prior to the hydrolysis and fermentation process. The different fine chemicals such as bioethanol, biobutanol, and biohydrogen production from microalgal carbohydrate are also discussed. The information from this review provides a framework for bioconversion of microalgal carbohydrate for biofuel and fine chemicals. This production could be beneficial for potential industrial implementation.