Effects of process parameters of various pretreatments on enzymatic hydrolysability of Ceiba pentandra (L.) Gaertn. (Kapok) fibre: A response surface methodology study

• Effect of pretreatments on sugar yield was studied by response surface methodology.
• Glucose yield was highly related to the chemical compositions of pretreated fibers.
• Pretreatments altered the physical structure of kapok fibers.
• Enzymatic hydrolysability of fibre was improved the most by alkaline treatment.
• Over 94% cellulose of the pretreated fibres was converted to glucose.

Kapok fibre is a promising raw material to produce sugar by enzymatic hydrolysis. In this work, effects of water, acid and alkaline pretreatments on the enzymatic sugar yield were studied through response surface methodology (RSM) and supported by the analysis of chemical compositions and physical structure of the fibre. For water pretreatment, reaction temperature and time were the independent variables while chemical concentration was also used as the third independent variable for acid and alkaline pretreatments. For all pretreatments, the enzymatic hydrolysis conditions were kept constant. The structure of pretreated fibre was also examined using scanning electron microscope (SEM). Results showed that water and acid pretreatments effectively dissolved hemicellulose of the fibre with the latter unveiled better results. The alkaline pretreatment resulted in the highest total glucose yield (g/kg of untreated fibre) as compared to water and acid pretreatments. SEM analysis illustrated that water and acid pretreatments led severe destruction of fibre structure; however, both of these pretreatments exhibited lower enhancement of enzymatic hydrolysability of kapok fibre as compared to that observed in alkaline pretreatment.