Improvement of Bioethanol Production From Low Grade and Damaged Longan Fruits With Thermal Pretreatment and Different Types of the Enzymatic Hydrolysis

Abstract

Pretreatment is a vital step in the enzymatic hydrolysis of biomass and the successive production of bioethanol. The present study is focused on thermal pretreatment (boiling & autoclave) methods of low grade and damaged longan fruits using three different types of the enzymatic sources from commercial cellulase, an enzyme from algae and mixed enzymes (i.e., commercial cellulase with algal enzyme). Total sugar production after the hydrolysis process from commercial cellulase, the enzyme from algae and mixed enzymes were 326.41 ± 08.97 g/L, 348.68 ± 01.95 g/L and 368.42 ± 01.16 g/L, respectively. Reducing sugar after the hydrolysis process generated from commercial cellulase, the enzyme from algae and mixed enzymes was 182.54 ± 03.05 g/L, 183.33 ± 04.70 g/L and 297.78 ± 02.94 g/L, respectively. Fermentation of these hydrolysate using Saccharomyces cerevisiae TISTR 5020 produced the highest ethanol production from using commercial cellulase, the enzyme from algae and mixed enzymes was 16.74 ± 0.62 g/L, 5.38 ± 0.54 g/L and 14.32 ± 1.89 g/L, respectively. Consequently, this study suggested that suitable pretreatment and hydrolysis processes are performing a significant role in bioethanol production from low grade and damaged longan fruits.