Response surface optimization of enzymatic hydrolysis of germinated brown rice for higher reducing sugar production

The hydrolysis of germ rice by the use of α-amylase and glucoamylase enzymes will help increase the reducing sugar content, reduce viscosity, and improve the yield of milk solution compared to the traditional extraction method. The liquefaction experiment was arranged with two factors, which are substrate ratio: α-amylase concentration and α-amylase concentration: different hydrolysis time. The saccharification experiment was carried out based on a multivariate model according to the Central Composite Design method. As a result, a 1 : 2 substrate ratio, 0.5% α-amylase concentration (approx. 11U/g starch) and 50 minutes hydrolysis time were selected as the basis for the next experiment. Analysis of variance in the regression model showed that the quadratic model was significant (p < 0.0001). Lack of fit (p > 0.05) this indicates that the model is suitable for all data. The reliability of the model R2 = 0.993 shows that the built regression model fits the data set 99.3%. CV = 1.19% indicated a better precision and reliability of the experiments carried out. Optimal conditions for hydrolysis of glucoamylase concentration of 0.399% (approx. 119.863U/g starch), temperature of 59.813°C and hydrolysis time of 160.468 minutes gave the highest DE content at 25.245% and higher than the non-enzymatic method (DE = 8.985 ± 0.062).