Microalgal biomass requires pre-treatment before fermentation to enhance bioetha­nol production. Biomass pre-treatment process is a major contributing factor to bio­ethanol production cost. The carbohydrates of microalgae are stored inside the cell walls and between the intercellular matrices [60]. Thus, it is necessary to rupture the microalgal cell walls so that the entrapped carbohydrates can be released and, if

Fig. 12 Process flow diagram of bioethanol production from microalgae

necessary, broken down into simple sugars to be utilized in the fermentation process. Cell disruption methods can be classified as mechanical, chemical and biological [44,47, 58]. Each of these methods is able to liberate the sugar molecules.