Effect of Microalgae Pretreatment Factors on Ethanol Yield

Researchers from the Bio Engineering Laboratory, Department of Chemical Engineering, Monash University (Australia) investigated the conditions for the acid pretreatment of microalgal biomass (Chlorococcum humicola) for biofuel-ethanol production. Pretreatment is a process of breaking down the complex carbohydrates in the biomass into (ethanol-fermentable) sugars. Acid treatment (in combination with heat) is one of the commonly-used pretreatment methods.

The researchers attempted to study the effects of different levels of acid concentration, temperature and pretreatment time on the amount of ethanol produced (after fermenting the sugars released from biomass pretreatment). Then they used a statistical approach (Response Surface Methodology, via Central Composite Design) to obtain the optimum pretreatment conditions. They found that at 140°C with 15 g/L of microalgae loading using 1% (v/v) of sulphuric acid for 30 minutes of pretreatment, the highest bioethanol of 7.20 g/L was obtained. On the other hand, the highest ethanol yield with a value 52wt% (g ethanol/g microalgae) was obtained at 160°C with 10 g/L of microalgae loading using 3% (v/v) of sulphuric acid for 15 minutes of pretreatment. Among the parameters, they found that temperature was the most critical factor during acid pre-treatment of microalgae for bioethanol production. The full paper is published in the journal, Process Biochemistry (URL above).