Direct Sucrose Hydrolysis in Sugarcane Juice with Immobilized Invertase: Multi-response Optimization Using Desirability Function on Conversion and Reactor Volumetric Productivity

Abstract

In this work, the hydrolysis of sucrose from clarified sugar cane juice and further purified juice was studied in a tubular reactor packed with immobilized invertase in calcium alginate. An analysis of response surface for the desirability function of conversion to glucose and fructose (Y_p/s) and reactor volumetric productivity (Q_p) in a Box–Behnken (incomplete 3⁴) experimental model for sucrose concentration in the juice, flow rate, temperature and pH value (pH), was conducted. The results showed that the combined process of purification by activated carbon and ultrafiltration produced a clarified and purified juice with Pol of 16.79 %, 18.95 °Brix, 7.23 of pH and 175 ICUMSA color units. Trapped invertase showed maximum activity at pH 4.0 and 50 °C, with K_m and V_max of 39.137 mM and 0.5266 mg total reducing sugar (TRS)/min mL, respectively. The desirability function for clarified juice presented optimum values of 75.18 % for TRS conversion and 2.809 g L⁻¹ min⁻¹ of volumetric productivity at 113.79 g L⁻¹ of sucrose in the juice, 0.82 mL min⁻¹ flow rate, 32.0 °C and 4.3 pH units. For purified juice, these values, were: 76.69 % of conversion and 2.88 g TRG L⁻¹ min⁻¹ for volumetric productivity at 120.9 g L⁻¹, 0.78 mL min⁻¹, 31.0 °C and 3.9 pH units.