Application of raw starch degrading enzyme from Laceyella sacchari LP175 for development of bacterial cellulose fermentation using colored rice as substrate

Abstract

Brown and black rice substrates were applied for sugar syrup production by the hydrolysis of raw starch degrading enzyme (RSDE) from Laceyella sacchari LP175 (300 U/mL) and commercial glucoamylase (GA, 2.0 U/mL) at 50 degrees C for 12 h using a simplex centroid mixture design. Results indicated that 300 g/L of substrates, consisting of 255 g/L Leum Pua glutinous rice and 45 g/L Black Jasmine rice, gave the highest sugar syrup production at 124.6 +/- 2.52 g/L with 2.00 +/- 0.05 mg GAE/mL of total phenolic content (TPC), equivalent to 0.42 +/- 0.01 g/g rice sample and 6.67 +/- 0.15 mg GAE/g rice sample, respectively. The obtained sugar syrup was used as the substrate for production of bacterial cellulose (Nata) by Komagataeibacter xylinus AGR 60 in a plastic tray at room temperature for 9 days. The fermentation medium containing 200 mL of rice syrup (25 g/L), 2.0 g of ammonium sulfate [(NH4)(2)SO4] and 0.4 mL glacial acetic acid yielded 1.1 +/- 0.08 cm thickness with 8.15 +/- 0.12 g of dry weight. The obtained bacterial cellulose from colored rice was characterized compared with bacterial cellulose from the conventional coconut juice by scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FTIR) which demonstrated that the sugar syrup from colored rice could use as substrate for a novel bacterial cellulose as a healthy product in the future through microbial enzyme technological process.