Production and development of vinegar fermentation from broken Riceberry rice using raw starch-degrading enzyme hydrolysis.

Broken Riceberry rice was used as a substrate for sugar syrup production by the hydrolysis of raw starch-degrading enzyme as a low-temperature amylase (iKnowZyme® LTAA, Thailand). Response surface methodology (RSM) with a central composite design (CCD) showed that an optimized substrate concentration of 250 g/L yielded 13°Brix of total soluble solid (TSS) content when incubated at 50 °C for 12 h. The major product from the broken Riceberry rice hydrolysis was glucose with lesser amounts of maltose and maltotriose. Maximum alcohol content (16% w/v) for broken Riceberry rice wine was obtained after fermentation with two mixed strains of Saccharomyces cerevisiae for 10 days. Scanning electron micrographs showed that yeast strains could grow on the solid residue of broken Riceberry rice that supported yeast cell survival under stress conditions. Broken Riceberry rice wine was used as the substrate for vinegar fermentation by Acetobacter aceti TISTR 354. Maximum acetic acid concentration was achieved at 5.4% when incubated at room temperature for 6 days, containing 10.92 mg/L and 965.53 ± 7.74 mL sample/g DPPH of anthocyanin content and antioxidant assay, respectively. Our finding revealed the feasibility of broken Riceberry rice substrate for sugar syrup, wine and vinegar production by raw starch-degrading enzyme hydrolysis which increased the value of low-cost agricultural crops through biotechnological processes. © King Abdulaziz City for Science and Technology 2020.