Conversion of Fibrous Sago (Metroxylon sagu) Waste into Fermentable Sugar via Acid and Enzymatic Hydrolysis

Abstract

The hydrolysis of dried-powdered fibrous sago waste by sulphuric acid and glucoamylase was studied. Both studies were carried out in an Erlenmeyer flask placed in a controlled temperature water bath. Samples were taken from the reaction flask at every 30 min interval for reducing sugar determination. The optimum condition for acid hydrolysis was found to be at 90°C, using 1.5 M acid concentration and reaction time of 120 min yielding 0.6234 g glucose g-1 waste. The kinetic parameters of acid hydrolysis in the Saeman`s model, were the rate constant (k1 = 0.01405 (1/min)), activation energy (Ea =120.40 (kJ mol-1)) and pre-exponential factor (A = 9.52x1016 (1/min)). The optimum condition for enzymatic hydrolysis using glucoamylase was found to be at enzyme concentration of 6 AGU mL-1 and reaction time of 30 min, yielding 0.5646 g glucose g-1 waste. The kinetic parameters in the competitive inhibition model corresponding to the optimum condition, namely the equilibrium constant for enzyme-inhibitor complex, Michaelis-Menten constant and maximum velocity, are 1.4727, 0.24175 and 1.35460 g L-1.min, respectively.