초록
<P><B>Abstract</B></P> <P>Major sugar constituents in young coconut husk were found to be glucans (0.30 g/g husk), while xylans were 0.10 g/g husk. Pre-treatments were carried out using phosphoric acid with dried coconut husk powder under steam heating. The effect of phosphoric acid on coconut husk hydrolysis was observed using acid concentrations of 0%, 1%, 5% and 10% (v/v). Soluble sugar concentration in hydrolysate was increasing proportional to acid concentration, as the total recovered solid decreases. FTIR and XRD analysis showed that acid hydrolysis led to the disruption of internal chemical bonds, causing coconut husk structural sugars to be released into the hydrolysate. Highest soluble sugar concentration, 29.9 g/L with a total suspended solid of 75.1 g/L, was obtained when the coconut husk was pre-treated with 10% phosphoric acid, and can be utilised for biohydrogen fermentation. Biotoxicity testing of the hydrolysates shows that half-maximal inhibition concentration of phosphoric acid was around 4.41% for a 24-h incubation and 3.80% for a 96-h incubation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Coconut husk sugar yield increases 18.3 g/L for 0% H<SUB>3</SUB>PO<SUB>4</SUB> to 29.9 g/L for 10% H<SUB>3</SUB>PO<SUB>4</SUB>. </LI> <LI> Biohydrogen yield of 0.68 mol H<SUB>2</SUB>/mol sugar is obtained with 1% H<SUB>3</SUB>PO<SUB>4</SUB> hydrolysate. </LI> <LI> The half-maximal inhibition concentration of H<SUB>3</SUB>PO<SUB>4</SUB> is 4.41% for 24-h incubation. </LI> <LI> The decrease order of biotoxicity is 10% H<SUB>3</SUB>PO<SUB>4</SUB> > 5% H<SUB>3</SUB>PO<SUB>4</SUB> > 1% H<SUB>3</SUB>PO<SUB>4</SUB> > 0% H<SUB>3</SUB>PO<SUB>4</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>