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The production of bioethanol from lignocellulosic biomass could be considered as an appropriate and economic option to remove environmental disasters and improve energy security. In fact, lignocellulosic material is mainly composed of cellulose, hemicellulose and lignin. Lignin works as the adhering prevents the bioconversion of cellulose into sugars and ultimately to ethanol. To address the problem, various chemical, physical, physicochemical and biological methods have been suggested. Enjoying convenient operating conditions, production of non-hazardous wastes, and having no harmful side effects, make the biological methods a potentially proper option. Unfortunately, the biological methods are slower and less efficient in comparison with the other processes. In the present study, an attempt is made to resolve this problem in an enzymatic degradation of lignin of a rice straw sample. Several peroxidase enzymes were produced by a white rot fungus, and their effects on lignin removal from the biomass samples were investigated in shaking flasks. Lignin concentration and enzymes' activity were measured by the acetyl bromide-soluble lignin spectrophotometric method and optical density method using special reagents, respectively. The results revealed that the enzymatic treatment could remove at least 30% of the lignin content of the lignocellulosic biomass. To achieve the maximum activity of the enzymes, The chemical composition of the culturing medium was optimized for the concentration of important metal ions including Cu2+, Mn2+ and Zn2+ through Box Behnken response surface methodology. The enzymes' activity at the obtained optimal conditions increased four times for Manganese peroxidase, and lignin peroxidase.

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Abstract
Bioactive peptides are considered specific protein fragments that are inactive within the sequence of the parent protein. After they are released by enzymatic hydrolysis, they may exert various physiological functions. In the present study, response surface methodology was used to optimize hydrolysis conditions for preparing protein hydrolysate from whey protein, using Alcalase 2.4L enzyme. The investigated factors were temperature, time and enzyme/substrate ratio which were selected in the range 43-52°C, 65-175 min and 45-90 AU/Kg protein, respectively to achieve maximum degree of hydrolysis. Experiments were designed according to the central composite design. Each of the studied variables had significant effect on degree of hydrolysis (p<0/05). The optimum conditions to achieve the highest degree of hydrolysis were temperature 49.02°C , time 174.28 min, and enzyme / substrate ratio 90AU/Kg protein. Under these conditions, hydrolysis degree was 41.57 %. Regression coefficient for, chariot models (Quadratic type) was, 0.95. The values indicated the high accuracy of the model to predict the reaction conditions for different variables.