Cellulase and acid-catalysed hydrolysis of Ulva fasciata, Hydropuntia dentata and Sargassum vulgare for bioethanol production

Abstract

Hydrolysis in bioethanol production is one of the most limiting stages in the entire production process since it is the stage where the sugars to be converted to ethanol are obtained. Ulva fasciata, Hydropuntia dentata and Sargassum vulgare seaweeds were examined in this study to determine the most efficient pretreatment, optimal hydrolysis conditions and predictive models with dilute sulphuric acid and cellulase enzyme as catalysts. Dilute acid pretreatment was found to be the most efficient in maximizing the catalytic efficiency of enzymes applied on all the three selected seaweeds. Ulva fasciata, however, was found to be efficiently hydrolysable without any form of pretreatment. The study also found dilute sulphuric acid hydrolysis to be less effective since it released up to 52.4% of reducing sugars in the seaweeds as compared to the 90.9% from hydrolysis with cellulase enzyme. Also, the most efficient regression model between the seaweed species studied was obtained for the enzymatic hydrolysis of U. fasciata with a correlation coefficient of 99.4%. This indicates a high precision in predicting the reducing sugar yields from the species within boundary conditions. Overall, the optimal enzymatic hydrolysis process was influenced most by substrate concentration for all three seaweeds examined.