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Abstract

Saccharification of biomass to fermentable sugar is a major constraint for bioethanol production due to high cost of enzyme production and complications associated with the removal of hearse acid, alkali and salts formed after neutralization. This led to the search for low cost enzyme and its combination with dilute acid to enhance biomass hydrolysis. In this study, the microalgal biomass was hydrolysed using amylase and cellulase enzymes produced by solid state and submerged fermentation processes. Saccharification of algal biomass was studied using dilute tetraoxosulphate (VI) acid, crude enzyme complex and a combination of both. The highest yield of reducing sugar of 0.63 mg/ml was obtained with the co-combination hydrolysis of acid and enzyme, followed by acid hydrolysis (0.41 mg/ml) while the least was found with enzyme hydrolysis (0.36 mg/ml). The hydrolysate of the algal pretreated biomass was used for bioethanol production by Saccharomyces cerevisiae and co-cultures of S. cerevisiae and Aspergillus niger. The highest ethanol yield of 0.33 mg/ml at a percentage of 10.82% v/v was obtained from hydrolysates pretreated with co-combination of dilute acid and crude enzyme complex. The result showed that crude enzyme can increase the yield of hydrolyzed microalgal biomass for bioethanol production.

Keywords: Crude enzyme; Fermentation; Hydrolysis; Microalgae; Saccharification