TABLE 2.

Coefficients determined for response models

Parameter	Response (y)a
	EPS concn (mg/ml)	CFU/ml	Time to endpoint (h)b
Constant (β0)	235.82	1.8 × 108	12.8
Temp (β1)	−4.64c	1.8 × 107c	−1.7d
pH (β2)	NIe	1.75 × 108d	−14.5d
Casitone (β3)	2.34c	NI	−0.3c
Temp × pH (β4)	NI	3.4 × 107f	0.9f
Temp × Casitone (β5)	−0.57c	NI	NI
pH × Casitone (β6)	NI	6.3 × 106	−0.2
Temp2 (β7)	−2.17f	NI	0.2f
pH2 (β8)	−20.91	7.5 × 107	9.9d
Casitone (β9)	0.24	9.4 × 105	0.05c
r2g	0.838	0.923	0.983
Ph	0.011	0.0005	0.0000

^aY = β₀ + β₁(T − 40) + β₂(pH − 5) + β₃(casitone − 20) + β₄(T − 40) (pH − 5) + β₅(T − 40)(casitone − 20) + β₆(pH − 5)(casitone − 20) + β₇(T − 40)² + β₈(pH − 5)² + β₉(casitone − 20)², where T is the temperature of fermentation (°C), pH is the pH of the medium during fermentation, and casitone is grams of Bacto-casitone per liter of growth medium. 

^bTime at which 90% of the glucose in the growth medium was utilized by the organism. Time to endpoint had a significant lack of fit (P < 0.05) with the response surface model. 

^cSignificantly different at P < 0.05. 

^dSignificantly different at P < 0.001. 

^eNI, not included. Inclusion of this coefficient in the model did not improve the fit. 

^fSignificantly different at P < 0.01. 

^gRegression coefficient of the model to predict the particular response variable. 

^hP value for the model to predict the particular response variable.