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Biosynthesis, purification, and biochemical properties of an alkaline-thermostable keratinase derived from Bacillus cereus J6

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17 mars 2025
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Figure 1.

Phylogenetic tree of Strain J6 constructed via Neighbor-joining method
Phylogenetic tree of Strain J6 constructed via Neighbor-joining method

Figure 2.

Keratinase production by B. cereus J6. A. Enzyme production profile; B, Feather; C, Nitrogen sources; D, Urea; E, Carbon sources; F, Lactose; G, Mineral salts; F, MgSO4.
Keratinase production by B. cereus J6. A. Enzyme production profile; B, Feather; C, Nitrogen sources; D, Urea; E, Carbon sources; F, Lactose; G, Mineral salts; F, MgSO4.

Figure 3.

Impact of cultural conditions on B. cereus J6 producing keratinase
Impact of cultural conditions on B. cereus J6 producing keratinase

Figure 4.

SDS-PAGE analysis of the purification of J6 keratinase. Lane M, protein marker; Lane 1, the crude B. cereus J6 keratinase; Lane 2, ASP; Lane 3, the target enzyme.
SDS-PAGE analysis of the purification of J6 keratinase. Lane M, protein marker; Lane 1, the crude B. cereus J6 keratinase; Lane 2, ASP; Lane 3, the target enzyme.

Figure 5.

Impact of temperature and pH
Impact of temperature and pH

Figure 6.

The enzymatic activity of the keratinase towards various substrates
The enzymatic activity of the keratinase towards various substrates

Figure 7.

The kinetics of the purified keratinase
The kinetics of the purified keratinase

Effects of chemicals on J6 keratinase

Chemicals Concentration Relative activity (%)
Na+ 5 mmol/L 102.59±2.78
K+ 5 mmol/L 99.03±2.93
Mn2+ 5 mmol/L 106.73±2.25
Ca2+ 5 mmol/L 122.56±2.19
Mg2+ 5 mmol/L 131.81±5.14
Zn2+ 5 mmol/L 118.52±3.52
Cu2+ 5 mmol/L 60.87±4.53
Al3+ 5 mmol/L 62.67±6.21
Fe2+ 5 mmol/L 52.89±5.35
Fe3+ 5 mmol/L 31.04±3.87
Tween 20 1% 115.67±3.14
Tween 60 1% 175.27±1.31
Tween 80 1% 150.16±2.31
Triton X-100 1% 106.06±0.52
SDS 1% 84.30±2.56
DTT 1 mmol/L 155.96±2.73
EDTA 1 mmol/L 5.05±2.21
PMSF 1 mmol/L Not detected

Results of orthogonal experiment

Number A B C D Keratinase yield (U/mL)
1 1 1 1 1 375.55±3.12
2 1 2 2 2 179.8±5.93
3 1 3 3 3 359.9±6.49
4 2 1 2 3 401.4±9.84
5 2 2 3 1 342.55±3.16
6 2 3 1 2 208.9±9.53
7 3 1 3 2 186.9±42
8 3 2 1 3 307.25±4.78
9 3 3 2 1 294.9±2.65
K1 305.08 321.28 297.23 337.67
K2 317.62 276.53 292.03 192.86
K3 263.02 288.9 296.45 356.18
R 54.6 32.38 5.2 163.32
Order of priority: D > A > B > C
Optimal Combination: A2B1C1D3

Orthogonal experimental design of four factors and three levels

Level Factor
A feather (g/L) B Lactose (g/L) C Urea (g/L) D MgSO4 (g/L)
1 7.5 2.5 7.5 0.9
2 10 5 10 1
3 12.5 7.5 12.5 1.1

Purification of the keratinase produced by B_ cereus J6

Procedures Protein quantity (mg) activity (U) Specific activity (U/mg) Purification fold Recovery rate (%)
Supernatant 53.25 24032 451.31 1.00 100
ASP 15.41 14256 925.19 2.05 59.32
DEAE-650 M chromatography 0.65 2739 4215.24 9.34 11.36