Purification and Characterization of Extracellular Protease from Halotolerant Bacterium Virgibacillus dokdonensis VITP14

Statistical optimization of thermostable alkaline protease from Bacillus cereus KM 05 using response surface methodology

OBJECTIVES

Proteases have gained great attention due to their enormous applications in food, tannery, detergent, photography and many other industries. Proteases rank third position in the production of enzymes. This paper targets to isolate a bacterium with high alkaline protease activity and optimization of its production conditions using Response Surface Methodology (RSM).

RESULTS

A bacterium isolated from soil contaminated with detergent exhibited clearance zone on skim milk agar medium with a protease activity of 22 U/ml. The bacterial strain was identified as Bacillus cereus KM05 and optimization of its production conditions were performed using statistical methods. Further optimization with Box Behnken design resulted in an increase in protease activity by 1.5-fold (28.6 U/ml). The protease enzyme was thermotolerant up to 70 °C with stability towards alkaline pH (pH 9). The enzyme was not affected by most of the metal ions and solvents. Moreover, the protease was also compatible with six commercial detergents tested. Densitometric analysis of the destained fabric materials following the detergent-enzyme treatment, revealed a stain removal efficiency of 97%.

CONCLUSION

The alkaline protease enzyme obtained was stable at different conditions with stain removal efficacy. Hence, the present alkaline protease could be used for detergent formulations.

Virgibacillus dokdonensis VITP14 produces α-amylase and protease with broader operational range but with differential thermodynamic stability

Extracellular α-amylase and protease were coproduced from halotolerant Virgibacillus dokdonensis VITP14 with banana peels (2% w/v) as substrate. The pH optima for α-amylase and protease were 6.5 and 7.0 respectively. The temperature optima of α-amylase and protease were 30°C and 50°C respectively. Both the enzymes were active in the presence of various metal ions (1 mM of Ni²⁺, Ca²⁺, Ba²⁺, Sr²⁺ and Mg²⁺⁾, detergents (Tween 20, Tween 80, Triton X-100) and other additives (2-mercaptoethanol and urea). Both the enzymes followed Michaelis-Menten type enzyme kinetics with V_max of 121.40 μmol min^-1 ml^-1 and 4.17 μmol min^-1 ml^-1 and K_m of 0.59 mg ml^-1 and 0.28 mg ml^-1 for amylase and protease respectively. Amylase showed higher activation energy for inactivation (75.55 kJ mol^-1 compared to 59.70 kJ mol^-1 for protease) and higher thermal stability (reflected by longer half-life 53.23 min compared to 0.11 min for protease) at 60°C. The coexistence of amylase and protease could be attributed to the difference in the optimum temperatures of activity and thermal stability of the two enzymes. This article is protected by copyright. All rights reserved.

Identification of a New Serine Alkaline Peptidase from the Moderately Halophilic Virgibacillus natechei sp. nov., Strain FarDT and its Application as Bioadditive for Peptide Synthesis and Laundry Detergent Formulations

A new peptidase designated as SAPV produced from a moderately halophilic Virgibacillus natechei sp. nov., strain FarDT was investigated by purification to homogeneity followed by biochemical and molecular characterization purposes. Through optimization, it was determined that the optimum peptidase activity was 16,000 U/mL. It was achieved after 36 h incubation at 35°C in the optimized enzyme liquid medium (ELM) at pH 7.4 that contains only white shrimp shell by-product (60 g/L) as sole energy and carbon sources. The SAPV enzyme is a monomer protein with a molecular mass of 31 kDa as estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and high-performance liquid chromatography (HPLC) gel filtration chromatography. The sequence of its NH2-terminal amino-acid residues showed homology with those of Bacillus peptidases S8/S53 superfamily. The SAPV showed optimal activity at pH 9 and 60°C. Irreversible inhibition of enzyme activity by diiodopropyl fluorophosphates (DFP) and phenylmethanesulfonyl fluoride (PMSF) confirmed its belonging to the serine peptidases. Considering its interesting biochemical characterization, the sapV gene was cloned, sequenced, and heterologously overexpressed in the extracellular fraction of E. coli BL21(DE3)pLysS. The biochemical properties of the recombinant peptidase (rSAPV) were similar to those of the native one. The highest sequence identity value (97.66%) of SAPV was obtained with peptidase S8 from Virgibacillus massiliensis DSM 28587, with 9 amino-acid residues of difference. Interestingly, rSAPV showed an outstanding and high resistance to several organic solvents than SPVP from Aeribacillus pallidus VP3 and Thermolysin type X. Furthermore, rSAPV exhibited an excellent detergent stability and compatibility than Alcalase 2.4 L FG and Bioprotease N100L. Considering all these remarkable properties, rSAPV has attracted the interest of industrialists.

Characterization of detergent compatible protease from halophilic Virgibacillus sp. CD6

A halophilic bacterium, Virgibacillus sp. strain CD6, was isolated from salted fish and its extracellular protease was characterized. Protease production was found to be highest when yeast extract was used as nitrogen source for growth. The protease exhibited stability at wide range of salt concentration (0-12.5%, w/v), temperatures (20-60 °C), and pH (4-10) with maximum activity at 10.0% (w/v) NaCl, 60 °C, pH 7 and 10, indicating its polyextremophilicity. The protease activity was enhanced in the presence of Mg²⁺, Mn²⁺, Cd²⁺, and Al³⁺ (107-122% relative activity), and with retention of activity > 80% for all of other metal ions examined (K⁺, Ca²⁺, Cu²⁺, Co²⁺, Ni²⁺, Zn²⁺, and Fe³⁺). Both PMSF and EDTA inhibited protease activity, denoting serine protease and metalloprotease properties, respectively. High stability (> 70%) was demonstrated in the presence of organic solvents and detergent constituents, and the extracellular protease from strain CD6 was also found to be compatible in commercial detergents. Proteinaceous stain removal efficacy revealed that crude protease of strain CD6 could significantly enhance the performance of commercial detergent. The protease from Virgibacillus sp. strain CD6 could serve as a promising alternative for various applications, especially in detergent industry.