Bioethanol production from coconut pulp residue using hydrothermal and postalkaline pretreatment.

Summary: The objective of this study is to explore the feasibility of sequential hydrothermal and alkaline pretreatment in improving enzymatic hydrolysis and sugar production of coconut pulp residue for bioethanol production. Hydrothermal pretreatment with the different heating duration of 20, 40, 60 minutes yielded 32.27, 27.51, and 26.72 g/L of total sugar, respectively. After posttreatment with 1%, 2%, and 3% alkaline treatment, the further increment of almost 90% on sugar production was observed. Compared to the single pretreatment, the combination of hydrothermal and alkaline pretreatment significantly affected the enzymatic hydrolysis. The optimum condition for efficient hydrolysis was 40 minutes hydrothermal pretreatment, followed by 1% NaOH posttreatment. At these conditions, the total and reducing sugar was 257.14 ± 0.92 and 102.86 ± 0.82 g/L and the maximum ethanol achieved was 27.19 g/L on the 48 hours of fermentation with efficiency and ethanol productivity of 51.83% and 0.57 g/L/h, respectively. [ABSTRACT FROM AUTHOR]