Preparation of coconut husk
Young coconut husks were used in the
study. After drying, they were cut into pieces
approximately 25 × 25 × 5 mm by a laboratory
chipper. The experiments used a factorial
completely randomized design with the two factors
being NaOH concentration (20, 25 and 30% based
on raw material dry weight) and boiling time (2
and 3 h), as shown in Table 1. All treatments were
performed at 100°C with two replications. Then,
the treated fiber was subjected to the 25% (based
on fiber dry weight) NaOH solution at 170°C for
3 h under pressure to obtain coconut husk pulp.
Excess chemical was removed by thorough
washing with water, the pulp was oven-dried and
used as substrate for further ethanol fermentation.