Effect of Pretreatment Methods on Enzymatic Kinetics of Ungelatinized Cassava Flour Hydrolysis

The energy-saving glucose production process from starchy sources was developed by replacing high-temperature, liquid-phase by low-temperature, solid-phase. Therefore, the enzymatic hydrolysis under gelatinization temperature at very high gravity (>= 300 g.L-1) of starchy substrates presents as an emerging technology. This study focused on the hydrolysis kinetics of cassava flour affected by different pretreatment methods. Cassava flour (dried, milled) was prepared in acetate buffer (pH 4.2) with starch concentration ranging from 10-30% (w/w). The mash was then pre-treated by three different methods for 30 min using heating (30, 40, 50 degrees C), enzyme (Viscozyme L 0.1%w/w) and microwave (3 x 20 s at 800 W). The suspension was then hydrolyzed with Stargen 002 (0.2%w/w) at 30 degrees C for 48 h. The enzyme adsorption kinetics was described by the Langmuir isotherm equation. The pretreatments at 50 degrees C and with enzyme resulted in the highest efficiency with the hydrolysis yield ranging from 76-79% after 48 h. The hydrolysis yield decreased to 67% (using microwave), 66% (at 45 degrees C), 61% (at 40 degrees C) and 59% (at 30 degrees C). The linear relationship between enzyme adsorption and produced glucose was demonstrated. The kinetics of glucose production was fitted by an empirical equation (analogy with Michaelis-Menten model) and allowed predicting the maximum hydrolysis yield.