Selective conversion of cassava mash to glucose using solid acid catalysts by sequential solid state mixed-milling reaction and thermo-hydrolysis

Solid acid catalysts have been recently studied in starch thermo-hydrolysis owing to their high catalytic activity, recyclability, ease to separate and environmental advantages. However, the solid state reaction of effective catalyst and starch molecules requires specific interaction between active sites in catalyst and α,1-4 glycosidic bonds in starch. Therefore, in this study catalyst mixed-milling was conducted prior to thermal hydrolysis to enhance glucose production efficiency. The results showed that catalyst mixed-milling process (24 h) followed by thermo-hydrolysis at 140 °C for 6 h using HA-L-SO₃H gave highest starch conversion of 93.72% corresponding to 37.45% glucose yield and 83% selectivity. From the kinetic study, the rate constant of cassava mash-to-oligomers conversion (k₁) using catalyst mixed-milling was 1.77 times higher than ball-milling without adding catalyst. This indicated that mixed-milling solid state reaction with effective catalyst significantly provided complete cassava mash conversion and enhanced selectivity as well as rate of starch depolymerization reaction.