Standardization of the Cultivation of Rhizopus arrhizus Using Agroindustrial Residues: High Production of Amylases in Pineapple Peel

Abstract

Amylases, crucial in various industries such as food, textile, and biofuels, require optimized production and biochemical characterization. Thus, this study aimed to produce amylases from Rhizopus sp. I 1.2.1, characterize the cultivation conditions and the synthesized enzyme. The fungus was molecularly identified with 99.06% homology in the LSU gene, 98.08% identity in the ITS region, and placed phylogenetically closer to Rhizopus arrhizus CBS 112,07. The LSU gene and ITS region sequences were deposited in GenBank. The CP medium was optimal for amylase production by Rhizopus arrhizus, with peak activity on the 6th day. Supplementation with urea significantly increased amylolytic activity by 110-fold. CP salts outperformed other salts in enzyme production, achieving a maximum amylase activity of 15.5 U/ml. The pH 6.0 was optimal for amylase production, with higher specific activity at pH 5.0. Pumpkin peel and pineapple peel were the best carbon sources for amylase production with an amylolytic activity of 18 and 16 U/mL, respectively. The amylase production showed a significant increase when pineapple peel was used in the presence of glucose 0.5% showing an activity of 22.4 U/mL, representing a 1.5- and 1.6-fold increase over the control. The optimal reaction of the amylase was observed at pH 6.0 and 60 °C. The enzyme remained stable for 240 minutes at 50–55 °C and at pH 4.0–7.0. Amylase was inhibited by glucose concentration and certain salts, but EDTA and K2SO4 increased activity by 25%. These results suggest industrial potential based on residual carbon source use, cultivation conditions, and crude enzyme stability.