Bioconversion of coconut husk fibre through biorefinery process of alkaline pretreatment and enzymatic hydrolysis

Abstract

Mature coconut husk (MCH) and young coconut husk (YCH) are abundantly generated as a by-product from coconut-based industry, which eventually lead to environmental pollution. However, the lignocellulose content in both types of coconut husk has the potential to be exploited as feedstock by way of biochemical processes through the concept of biorefinery. In this study, the MCH and YCH were subjected to alkaline pretreatment by sodium hydroxide (NaOH). Subsequently, enzymatic hydrolysis using Accellerase® 1500 was conducted to convert the lignocellulosic materials into fermentable sugars. The changes in surface morphology of MCH and YCH throughout the process were also observed. Alkaline pretreatment successfully removed 20.15 and 31.17% of lignin content in MCH and YCH, respectively. The increase in cellulose content after alkaline pretreatment was detected around 17% for MCH and 20% for YCH. For optimisation of enzymatic hydrolysis, 10% enzyme loading for 24 h showed significantly higher (p < 0.05) reducing sugar content in MCH and YCH hydrolysates of 19.17 g/L and 24.33 g/L, respectively. The efficiency of the hydrolysis process was proven by high sugar recovery of 71.23% for MCH and 89.49% for YCH. Concurrently, the morphological analysis showed the effect of the treatments on the surface of MCH and YCH, where the structure became swollen and collapsed as the majority of lignocellulosic materials were digested. Therefore, the study pointed out the potential of reutilising MCH and YCH as alternative resources for the future biochemical process feedstock.