Purification and biochemical characterization of halophilic, alkalithermophilic protease AbCP from Alkalibacillus sp. NM-Fa4

Purification and biochemical characterization of a novel thermostable and halotolerant subtilisin SAPN, a serine protease from Melghiribacillus thermohalophilus Nari2AT for chitin extraction from crab and shrimp shell by-products

The present study investigates the purification and biochemical characterization of a novel extracellular serine alkaline protease, subtilisin (called SAPN) from Melghiribacillus thermohalophilus Nari2A^T. The highest yield of protease (395 IU/g) with white shrimp shell by-product (40 g/L) as a unique source of nutriments in the growth medium was achieved after 52 h at 55 °C. The monomeric enzyme of about 30 kDa was purified to homogeneity by ammonium sulfate fractionation, heat treatment, followed by sequential column chromatographies. The optimum pH and temperature values for subtilisin activity were pH 10 and 75 °C, respectively, and half lives of 9 and 5 h at 80 and 90 °C, respectively. The sequence of the 25 NH₂-terminal residues pertaining of SAPN exhibited a high homology with those of Bacillus subtilisins. The inhibition by DFP and PMSF indicates that this enzyme belongs to the serine proteases family. SAPN was found to be effective in the deproteinization (DDP %) of blue swimming crab (Portunus segnis) and white shrimp (Metapenaeus monoceros) by-products, with a degree of 65 and 82%, respectively. The commercial and the two chitins obtained in this work showed a similar peak pattern in Fourier-Transform Infrared (FTIR) analysis, suggesting that SAPN is suitable for the bio-production of chitin from shell by-products.

Isolation of halophilic bacteria associated with saline and alkaline-sodic soils by culture dependent approach

Cultivable halophilic microorganisms were isolated and identified from saline and alkaline-sodic soils: Cuatro Cienegas, Sayula and San Marcos lakes. Physicochemical characteristics of soils were determined to understand the relationship between those and the microorganisms isolated. The Cuatro Cienegas soils had a neutral pH, EC of 2.3–8 dS cm⁻¹, classified as moderately saline. Whereas, the soils from Sayula and San Marcos lakes, had an alkaline pH, EC 15 to 65 dS m⁻¹, typical of saline-sodic. We identified 23 cultivable halophilic bacteria using 16s rDNA, being Halobacillus sp., Marinococcus sp., and Alkalibacillus sp. the predominant genus by culture dependent approach. We found a correlation between the soils anion and cation content with the occurrence of different genus of halophilic bacteria in each studied site. Alkalibacillus sp. was predominant in Sayula and San Marcos lakes and was related to the high Na⁺ content; while Bacillus sp. and Halobacillus sp. were predominant in Cuatro Cienegas, their occurrence was related to a high content of Ca²⁺, Mg²⁺, and SO₄^2-.

Bioprocess optimization for production of thermoalkali-stable protease from Bacillus subtilis K-1 under solid-state fermentation

Cost-effective production of proteases, which are robust enough to function under harsh process conditions, is always sought after due to their wide industrial application spectra. Solid-state production of enzymes using agro-industrial wastes as substrates is an environment-friendly approach, and it has several advantages such as high productivity, cost-effectiveness, being less labor-intensive, and less effluent production, among others. In the current study, different agro-wastes were employed for thermoalkali-stable protease production from Bacillus subtilis K-1 under solid-state fermentation. Agricultural residues such as cotton seed cake supported maximum protease production (728 U ml(-1)), which was followed by gram husk (714 U ml(-1)), mustard cake (680 U ml(-1)), and soybean meal (653 U ml(-1)). Plackett-Burman design of experiment showed that peptone, moisture content, temperature, phosphates, and inoculum size were the significant variables that influenced the protease production. Furthermore, statistical optimization of three variables, namely peptone, moisture content, and incubation temperature, by response surface methodology resulted in 40% enhanced protease production as compared to that under unoptimized conditions (from initial 728 to 1020 U ml(-1)). Thus, solid-state fermentation coupled with design of experiment tools represents a cost-effective strategy for production of industrial enzymes.

Biochemical characterization of a halophilic, alkalithermophilic protease from Alkalibacillus sp. NM-Da2

An extracellular, halophilic, alkalithermophilic serine protease from the halo-alkaliphilic Alkalibacillus sp. NM-Da2 was purified to homogeneity by ethanol precipitation and anion-exchange chromatography. The purified protease was a monomeric enzyme with an approximate molecular mass of 35 kDa and exhibited maximal activity at 2.7 M NaCl, pH^55 °C 9 and 56 °C. The protease showed great temperature stability, retaining greater than 80 % of initial activity after 2 h incubation at 55 °C. The protease was also extremely pH tolerant, retaining 80 % of initial activity at pH^55 °C 10.5 after 30 min incubation. Protease hydrolyzed complex substrates, displaying activity on yeast extract, tryptone, casein, gelatin and peptone. Protease activity was inhibited at casein concentrations greater than 1.2 mg/mL. The enzyme was stable and active in 40 % (v/v) solutions of isopropanol, ethanol and benzene and was stable in the presence of the polysorbate surfactant Tween 80. Activity was stimulated with the oxidizing agent hydrogen peroxide. Inhibition with phenyl methylsulfonylfluoride indicates it is a serine protease. Synthetic saline wastewater treated with the protease showed 50 % protein removal after 5 h. Being halophilic, alkaliphilic and thermophilic, in addition to being resistant to organic solvents, this protease has potential for various applications in biotechnological and pharmaceutical industries.

Halophiles: biology, adaptation, and their role in decontamination of hypersaline environments

The unique cellular enzymatic machinery of halophilic microbes allows them to thrive in extreme saline environments. That these microorganisms can prosper in hypersaline environments has been correlated with the elevated acidic amino acid content in their proteins, which increase the negative protein surface potential. Because these microorganisms effectively use hydrocarbons as their sole carbon and energy sources, they may prove to be valuable bioremediation agents for the treatment of saline effluents and hypersaline waters contaminated with toxic compounds that are resistant to degradation. This review highlights the various strategies adopted by halophiles to compensate for their saline surroundings and includes descriptions of recent studies that have used these microorganisms for bioremediation of environments contaminated by petroleum hydrocarbons. The known halotolerant dehalogenase-producing microbes, their dehalogenation mechanisms, and how their proteins are stabilized is also reviewed. In view of their robustness in saline environments, efforts to document their full potential regarding remediation of contaminated hypersaline ecosystems merits further exploration.

Characterization of a salt-activated protease with temperature-dependent secretion in Stenotrophomonas maltophilia FF11 isolated from frozen Antarctic krill

Seafood is sometimes wasted due to the growth of psychrotolerant microbes which secrete proteases and break down proteins. Stenotrophomonas maltophilia FF11, isolated from frozen Antarctic krill, grows at a wide range of temperatures and secretes more proteases at low temperatures. According to zymogram analysis, two kinds of proteases were produced from this strain. A major protease was produced largely at 15 °C, but not at 37 °C. The temperature-dependent secreted protease was purified to homogeneity. Its molecular mass was determined at 37.4 kDa and its amino acid sequence was also obtained. This protease is a member of the subtilase group according to the NCBI blast analysis. The enzyme was highly stable at high salt concentration (4 M). Interestingly, its activity increased about 1.6-fold under high salt condition. The enzyme remains active and stable in different organic solvents (50 %, v/v) such as dimethylsulfoxide, dimethyl formamide, dioxane and acetone. These properties may provide potential applications in quality control for sea foods, in protein degradation at high salt concentration, in biocatalysis and biotransformation within non-aqueous media, such as detergent and transesterification.

Purification and characterization of an extracellular haloalkaline serine protease from the moderately halophilic bacterium, Bacillus iranensis (X5B)

This study reports the purification and characterization of an extracellular haloalkaline serine protease from the moderately halophilic bacterium, Bacillus iranensis, strain X5B. The enzyme was purified to homogeneity by acetone precipitation, ultrafiltration and carboxymethyl (CM) cation exchange chromatography, respectively. The purified protease was a monomeric enzyme with a relative molecular mass of 48-50 kDa and it was inhibited by PMSF indicating that it is a serine-protease. The optimum pH, temperature and NaCl concentration were 9.5, 35 °C and 0.98 M, respectively. The enzyme showed a significant tolerance to salt and alkaline pH. It retained approximately 50% of activity at 2.5 M NaCl and about 70% of activity at highly alkaline pH of 11.0; therefore, it was a moderately halophilic and also can be activated by metals, especially by Ca(2+). The specific activity of the purified protease was measured to be 425.23 μmol of tyrosine/min per mg of protein using casein as a substrate. The apparent K m and V max values were 0.126 mM and 0.523 mM/min, respectively and the accurate value of k cat was obtained as 3.284 × 10(-2) s(-1). These special and important characteristics make this serine protease as valuable tool for industrial applications.

Deproteinization potential and antioxidant property of haloalkalophilic organic solvent tolerant protease from marine Bacillus sp. APCMST-RS3 using marine shell wastes

The current increase in the vast amount of marine crustacean shell waste produced by the fish processing industries has led to the need to find new methods for its disposal. Hence, the present study was carried out via marine shell wastes as substrate for protease production. The maximum production (4000.65 U/ml) from Bacillus sp. APCMST-RS3 was noticed in 3:1% shrimp and oyster shell powder (SOSP) as substrate. Purified protease showed 53.22% and 22.66% enzyme yield; 3.48 and 8.49 fold purity with 40 kDa molecular weight; whereas, its Km and Vmax values were 0.6666 g/l, 1111.11 U/ml. This enzyme showed optimum activity at pH 9 and 60 °C temperature. Also, it retained maximum protease activity in the presence of NaCl (2.5 M), surfactants (Tween 20, 40, 60, 80 and SDS) and metal ions (MnCl2, CaCl2, HgCl2 and BaCl2) and solvents. The candidate bacterium effectively deproteinized (84.35%) shrimp shell and its antioxidant potentials.