Table 2.

Experimental values of extracellular protease activity (U/mL) and biomass concentration (g/L) at the end of batch runs carried out in flasks using different organic nitrogen sources, according to the 2⁵⁻¹ fractional factorial design depicted in Table 1.

Run	X1 (g/L)	X2 (g/L)	X3 (g/L)	X4 (g/L)	X5 (g/L)	Protease activity (U/mL)	Biomass concentration (g/L)
1	0	0	0	0	2.5	56.3 ± 10.2	0.78 ± 0.03
2	2.5	0	0	0	0	61.1 ± 6.8	0.53 ± 0.02
3	0	2.5	0	0	0	233.5 ± 2.9	0.63 ± 0.10
4	2.5	2.5	0	0	2.5	441.5 ± 35.5	8.05 ± 0.2
5	0	0	2.5	0	0	179.3 ± 32.0	0.60 ± 0.10
6	2.5	0	2.5	0	2.5	420.5 ± 47.6	11.73 ± 0.38
7	0	2.5	2.5	0	2.5	304.7 ± 21.3	12.29 ± 0.47
8	2.5	2.5	2.5	0	0	422.8 ± 47.8	12.79 ± 0.50
9	0	0	0	2.5	0	41.7 ± 15.7	0.60 ± 0.03
10	2.5	0	0	2.5	2.5	165.9 ± 0.2	5.54 ± 0.09
11	0	2.5	0	2.5	2.5	163.8 ± 5.0	6.05 ± 0.16
12	2.5	2.5	0	2.5	0	244.9 ± 1.4	11.61 ± 0.34
13	0	0	2.5	2.5	2.5	142.8 ± 3.4	6.21 ± 0.23
14	2.5	0	2.5	2.5	0	324.2 ± 36.9	12.76 ± 0.52
15	0	2.5	2.5	2.5	0	160.7 ± 30.2	12.22 ± 0.51
16	2.5	2.5	2.5	2.5	2.5	175.1 ± 3.6	15.30 ± 0.52

Under the same conditions (48 h of growth at 250 rpm, 20 °C and 20 g/L of dextrose), the protease activity of R. mucilaginosa CBMAI 1528 on Sabouraud dextrose medium was 279.4 ± 12.4 U/mL, and the biomass concentration 6.8 ± 0.3 g/L. X₁: casein tryptone (g/L), X₂: peptone from animal tissue (g/L), X₃: yeast extract (g/L), X₄: casamino acids (g/L), X₅: peptone from gelatin (g/L).