Enzymatic hydrolysis of microalgal biomass for bioethanol production

Abstract Increasing global energy demands and the potential for significant climate change have led to burgeoning interest in alternative fuels which are sustainable, environmentally friendly and cost efficient. One of the key options is to produce bioethanol from renewable biomass. Due to its numerous advantages, including fast growth rate, non-edibility, and the ability to accumulate substantial amounts of carbohydrates, microalgae, a second generation cellular biomass, have the potential to be used as a fermentation feedstock for bioethanol production. The present study examines the enzymatic hydrolysis of Chloroccum sp. by using cellulase obtained from Trichoderma reesei, ATCC 26921. The hydrolysis was conducted under varying conditions of temperature, pH and substrate concentration, with constant enzyme dosage. The kinetics of hydrolysis was fitted with Michaelis–Menten's model of rapid equilibrium. The highest glucose yield of 64.2% (w/w) was obtained at a temperature of 40 °C, pH 4.8, and a substrate concentration of 10 g/L of microalgal biomass. Comparative kinetic studies on glucose and cellobiose formation showed twice as fast glucose production than cellulobiose. The value of Km,app was higher for the hydrolysis of cellobiose (Km,app = 15.18 g/L) compared to that of the substrate (Km,app = 1.48 g/L), thus displaying a competitive type of inhibition. The results were in keeping with the obtained reaction velocities. Overall, the enzymatic hydrolysis process proved to be an effective mechanism to enhance the saccharification process of microalgal biomass.

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