Kinetics of Enzymatic Hydrolysis of Lignocellulosic Materials at Different Concentrations of Substrat

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The kinetics of enzymatic hydrolysis in an acetate buffer of two substrates — lignocellulosic material from miscanthus and from oat husk (OH) — was studied at different concentrations of the substrates. The substrates were produced by a single-step treatment with a dilute solution of nitric acid. The content of a nonhydrolyzable component — acid-insoluble lignin — was 11 and 14 % for miscanthus and OH, respectively.As a catalyst, a multi-enzymatic composition of commercially available enzyme preparations Tsellolyuks-A and Bryuzaym BGX was used. It is shown that the treatment with nitric acid produces reactive substrates for enzymatic hydrolysis. Scientific novelty of the results is confirme d by Russian patent RF 2533921. The kinetics of enzymatic hydrolysis of substrates in the acetate buffer can be described by a mathematical model based on the modified Michaelis-Menten equation. On the basis of experimental data, basic kinetic constants were determined for both substrates. The equilibrium concentrations of reducing substances (RS) were calculated for substrates depending on their initial concentration. It is found that the initial rate of the enzymatic hydrolysis for the OH-derived lignocellulosic material is 1 g/(L·h) above that for the miscanthus-derived lignocellulose material in the entire range of studied substrate concentrations (33,3ч120,0 g/L). It is shown that with an increase in the initial substrate concentration from 33,3 to 120,0 g/L, the RS yield decreases 1,5–2,0-fold because of substrate inhibition. At low initial concentrations, the yields of RS for both substrates are similar. In contrast, at the high initial concentration of substrate (120,0 g/L), the yield of RS from the miscanthus-derived lignocellulosic material is about 20 % higher than that from the OH-derived material. The obtained experimental dependence and the suggested mathematical model allow one to optimize initial concentrations of the substrate for efficient enzymatic hydrolysis.