Optimization of the Nutritional Parameters for Enhanced Production of B. subtilis SPB1 Biosurfactant in Submerged Culture Using Response Surface Methodology

Table 3

Estimated effect, regression coefficient, and corresponding 𝑡, 𝑃 values and confidence level of each variable described for biosurfactant production in Plackett Burman design experiments.

Noun	Coefficient	F Inflation	SE	𝑡.exp	𝑃 value	Confidence level (%)	Signification
𝑏0	1.418		0.209	−1.307	0.2480	75.2	NS
𝑏1	0.551	1.00	0.003	7.447	0.0006	99.94	***
𝑏2	0.415	1.00	0.023	5.611	0.0024	99.76	**
𝑏3	0.013	1.00	0.023	0.186	0.8597	14.03	NS
𝑏4	0.107	1.00	0.020	1.446	0.2077	79.23	NS
𝑏5	0.184	1.00	0.051	2.490	0.0551	94.49	NS
𝑏6	0.227	1.00	0.044	2.495	0.0547	94.53	NS
𝑏7	0.520	1.00	0.061	7.027	0.0009	99.91	***
𝑏8	0.188	1.00	10.285	2.550	0.0512	94.88	NS
𝑏9	−0.216	1.00	10.285	−2.922	0.0329	96.71	*
𝑏10	−0.004	1.00	10.285	−0.066	0.9499	5.01	NS
𝑏11	−0.240	1.00	10.285	−3.246	0.0227	97.73	*

With SE is the standard error and 𝑡.exp is the value of variables determined by Student’s 𝑡-test.
(***): significant at the level > 99.9% (for 0.0001<𝑃 value <0.001).
(**): significant at the levels comprised between 99% and 99.9% (for 0.001<𝑃 value <0.01).
(*): significant at the levels comprised between 95% and 99% (for 0.01<𝑃 value <0.05).
NS: NonSignificant (Terms were considered NS for 𝑃 value >0.05).