Background: The current utilization of biomass to produce energy represents only about 2% of the annual production of biomass in the world. Recently, algae have received much attention due to the shortage of energy and mitigation of carbon dioxide, and are therefore considered as an alternative source of renewable energy. However, a major obstacle in the use of these biomasses is the highly complex composition of their cell walls. In algae, they are mainly composed of complex polysaccharides, like cellulose and hemicellulose, and proteins. All these macromolecules cannot be depolymerized by anaerobic bacteria for biofuel production. On the other hand, depolymerization of polysaccharides and proteins supplies nutrients for bacteria to
produce bioethanol through fermentation or biogas by anaerobic digestion. To this aim, a pretreatment step
is needed to break down the cell wall components, although the type of treatment depends on the specific composition of the adopted algae, as this can vary from species to species. Relevant studies have reported the efficiency of enzymatic pre-treatment to break up algae cell walls by combining the action of various
cellulolytic enzymes. This strategy has been employed to enhance biofuel production and represents a promising alternative to other cell disruption methods.
Results: This review provides an overview of the advantages of using algae for biofuel production and the current understanding of enzymatic pre-treatments in enhancing cellulose and hemicellulose degradation into fermentable monosaccharides. However, the performance of this approach depends on microalgae cell wall complexity.
Conclusion: Given the diversity of algal cell wall composition, a thorough understanding of all possible enzymatic reactions one could exploit to depolymerize cell walls is a valid tool for efficient biofuel production.