K means the sum of the cor-responding level value under each factor; R means range which represents the influence of the each factor, which is expressed by R = Kmax/3 − Kmin/3.
Obviously, the influential order of each variable on the degradation of KG was C ≈ B > D > A by comparing R values in Table 2.
Owing to the value of R for C and B factors being high, it was shown that the contribution of C and B factors for degradation were significant.
Thus, pH and temperature have the greatest influence on degradation of KG.
Furthermore, according to the values of R for the other two factors, it could be found that the reaction time and enzyme concentration have a weak influence on the degradationas compared with pH and temperature.
For each variance, the optimum level of each variable was A1B2C2D3.
With consideration of the cost, the optimum reaction condition was obtained as follows:reaction time 2 h, reaction temperature 50◦C, pH 6.0, and enzyme concentration 150 U/g.