Optimization of Milk-Based Medium for Efficient Cultivation of Bifidobacterium pseudocatenulatum G4 Using Face-Centered Central Composite-Response Surface Methodology

Table 4

The steepest ascent coordination path for all chosen factors at coded and natural levels.

Step	Coded factor^a		Natural factor^b (% wt/vol)		Maximum biomass (log10 cfu/mL)^e
	𝜀1	𝜀2	𝑥1	𝑥2
Base^c	0	0	4	1.75	5.77±0.24
Δ^d	1	0.28	2	0.14	4.05±0.09
Base + Δ	1	0.28	6	1.89	7.68±0.17
Base + 2Δ	2	0.56	8	2.03	7.66±0.68
Base + 3Δ	3	0.84	10	2.17	7.65±0.26
Base + 4Δ	4	1.12	12	2.31	7.63±0.66
Base + 5Δ	5	1.40	14	2.45	7.61±0.04

aCoded factor 𝜀₁: skim milk, 𝜀₂: yeast extract.
^bNatural factor 𝑥₁: skim milk, 𝑥₂: yeast extract.
^cBased: 0 for coded factor and middle point for natural factor.
^dMovement units (coded factor 𝜀₁: 0.1/0.1, 𝜀₂: 0.3/1.09) (natural factor: coded factor 𝑥 lower point).
^eMaximum biomass of B. pseudocatenulatum G4 (log₁₀ cfu/mL) at 21 h of cultivation period. Values are mean of triplicates.