Table 3. Polynomial equations calculated by RSM program for the fermentation condition of black soybean

Responses	Second order polynomials1)	R2	p-value
Yield	Y1 = 82.962857 + 22.472024X1 + 0.028818X2 − 51.008929X1X1 + 0.037500X2X1 − 0.000578X2X2	0.9027	p<0.05
Amino nitrogen content	Y2 = 206.091429 + 5.013095X1 + 0.914149X2 + 351.839286X1X1 − 1.112500X2X1 − 0.001148X2X2	0.9150	p<0.05
β-Glucan content	Y3 = 1.850714 − 0.088452X1 + 0.095458X2 − 9.055357X1X1 + 0.103625X2X1 − 0.001035X2X2	0.8439	p<0.10
Methionine content	Y4 = −92.274286 + 1397.610714X1 + 9.158970X2 − 2302.517857X1X1 − 1.748750X2X1 − 0.071800X2X2	0.9145	p<0.05
Cystine content	Y5 = 88.170000 + 1282.379167X1 + 8.863687X2 − 2131.937500X1X1 − 0.757500X2X1 − 0.070464X2X2	0.8457	p<0.10

X₁, enzyme concentration; X₂, fermentation time.