A Novel Thermostable and Alkaline Protease Produced from Bacillus stearothermophilus Isolated from Olive Oil Mill Sols Suitable to Industrial Biotechnology

Improvement of branched-chain amino acid production by isolated high-producing protease from Bacillus amyloliquefaciens NY130 on isolated soy/whey proteins and their muscle cell protection

Branched-chain amino acids (BCAAs) are vital components of human and animal nutrition that contribute to the building blocks of proteins. In this study, 170 protease-producing strains were isolated and screened from soy-fermented foods. Bacillus amyloliquefaciens NY130 was obtained from Cheonggukjang with high production of BCAAs. Optimal production of protease from B. amyloliquefaciens NY130 (protease NY130) was achieved at 42 °C and pH 6.0 for 21 h. It was purified and determined as 27- and 40 kDa. Protease NY130 showed maximum activity at pH 9.0 and 45 °C with Km value of 10.95 mg for ISP and 1.69 mg for WPI. Protease-treated ISP and WPI showed increased sweetness and saltiness via electronic tongue analysis and enhanced the protective effect against oxidative stress in C2C12 myocytes by increasing p-mTOR/mTOR protein expression to 160%. This work possesses potential in producing BCAAs by using protease for utilization in food.

Agro-industrial Waste Utilization, Medium Optimization, and Immobilization of Economically Feasible Halo-Alkaline Protease Produced by Nocardiopsis dassonvillei Strain VCS-4

The oceanic actinobacteria have strong potential to secrete novel enzymes with unique properties useful for biotechnological applications. The Nocardiopsis dassonvillei strain VCS-4, associated with seaweed Caulerpa scalpeliformis, was a halo-alkaline protease producer. Further investigation focuses on medium optimization and the use of agro-industrial waste for economically feasible, high-yield protease production. A total of 12 experimental runs were designed using Minitab-20 software and Placket-Burman design. Among the 7 physicochemical parameters analyzed, incubation time and gelatin were detected as significant factors responsible for higher protease production. Incubation time and gelatin were further analyzed using OVATs. Optimal protease production was achieved with 2% gelatin, 0.1% yeast extract, 0.1% bacteriological peptone, 7% NaCl, pH 8, 5% inoculum, and a 7-day incubation period, resulting in a maximum protease activity (Pmax) of 363.97 U/mL, generation time of 11.9 h, specific growth rate of 0.161 g/mL/h, and protease productivity (Qp) of 61.65 U/mL/h. Moreover, utilizing groundnut cake as an agro-industrial waste led to enhanced production parameters: Pmax of 408.42 U/mL, generation time of 9.74 h, specific growth rate of 0.361 g/mL/h, and Qp of 68.07 U/mL/h. The immobilization of crude protease was achieved using Seralite SRC 120 as a support matrix resulting in 470.38 U/g immobilization, 88.20% immobilization yield, and 28.90% recovery activity. Characterization of both crude and immobilized proteases revealed optimal activity at pH 10 and 70 °C. Immobilization enhanced the shelf-life, reusability, and stability of VCS-4 protease under extreme conditions.

Molecular Cloning, Characterization, and Application of Organic Solvent-Stable and Detergent-Compatible Thermostable Alkaline Protease from Geobacillus thermoglucosidasius SKF4

Several thermostable proteases have been identified, yet only a handful have undergone the processes of cloning, comprehensive characterization, and full exploitation in various industrial applications. Our primary aim in this study was to clone a thermostable alkaline protease from a thermophilic bacterium and assess its potential for use in various industries. The research involved the amplification of the SpSKF4 protease gene, a thermostable alkaline serine protease obtained from the Geobacillus thermoglucosidasius SKF4 bacterium through polymerase chain reaction (PCR). The purified recombinant SpSKF4 protease was characterized, followed by evaluation of its possible industrial applications. The analysis of the gene sequence revealed an open reading frame (ORF) consisting of 1,206 bp, coding for a protein containing 401 amino acids. The cloned gene was expressed in Escherichia coli. The molecular weight of the enzyme was measured at 28 kDa using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The partially purified enzyme has its highest activity at a pH of 10 and a temperature of 80°C. In addition, the enzyme showed a half-life of 15 h at 80°C, and there was a 60% increase in its activity at 10 mM Ca2+ concentration. The activity of the protease was completely inhibited (100%) by phenylmethylsulfonyl fluoride (PMSF); however, the addition of sodium dodecyl sulfate (SDS) resulted in a 20% increase in activity. The enzyme was also stable in various organic solvents and in certain commercial detergents. Furthermore, the enzyme exhibited strong potential for industrial use, particularly as a detergent additive and for facilitating the recovery of silver from X-ray film.

Biochemical Characterization and Application of a Detergent Stable, Antimicrobial and Antibiofilm Potential Protease from Bacillus siamensis

Proteases are important enzymes that are engaged in a variety of essential physiological functions and have a significant possible use in industrial applications. In this work, we reported the purification and biochemical characterization of a detergent stable, antimicrobial, and antibiofilm potential protease (SH21) produced by Bacillus siamensis CSB55 isolated from Korean fermented vegetable kimchi. SH21 was purified to obtain homogeneity via ammonium sulfate precipitation (40-80%), Sepharose CL-6B, and Sephadex G-75 column. By analyzing the SDS-PAGE and zymogram, it was determined that the molecular weight was around 25 kDa. The enzyme activity was almost completely inhibited in the presence of PMSF and DFP, which indicated that it was a member of the serine protease family. SH21 showed excellent activity with a broad range of pH and temperature, with its maximum pH of 9.0 and temperature of 55 °C. The enzyme had estimated K_m and V_max values of 0.197 mg/mL and 1.22 × 10³ U/mg, respectively. In addition, it preserved good activity in the presence of different organic solvents, surfactants, and other reagents. This enzyme showed good antimicrobial activity that was evaluated by MIC against several pathogenic bacteria. Furthermore, it exhibited strong antibiofilm activity as determined by MBIC and MBEC assay and degraded the biofilms, which were analyzed by confocal microscopic study. These properties established that SH21 is a potent alkaline protease that can be used in industrial and therapeutic applications.

Two-Step Purification and Partial Characterization of Keratinolytic Proteases from Feather Meal Bioconversion by Bacillus sp. P45

This study aimed to purify and partially characterize a keratinolytic protease produced by Bacillus sp. P45 through bioconversion of feather meal. Crude protease extract was purified using a sequence of an aqueous two-phase system (ATPS) in large volume systems (10, 50, and 500 g) to increase obtaining purified enzyme, followed by a diafiltration (DF) step. Purified protease was characterized in terms of protein profile analysis by SDS-PAGE, optimum temperature and pH, thermal deactivation kinetics at different temperatures and pH, and performance in the presence of several salts (NaCl, CaCl2, MnCl2, CaO, C8H5KO4, MgSO4, CuSO4, ZnSO4, and FeCl3) and organic solvents (acetone, ethanol, methanol, acetic acid, diethyl ether, and formaldehyde). ATPS with high capacities resulted in purer protease extract without compromising purity and yields, reaching a purification factor up to 2.6-fold and 6.7-fold in first and second ATPS, respectively, and 4.0-fold in the DF process. Recoveries were up to 79% in both ATPS and reached 84.3% after the DF step. The electrophoretic analysis demonstrated a 25–28 kDa band related to keratinolytic protease. The purified protease’s optimum temperature and pH were 55 °C and 7.5, respectively. The deactivation energy (Ed) value was 118.0 kJ/mol, while D (decimal reduction time) and z (temperature interval required to reduce the D value in one log cycle) values ranged from 6.7 to 237.3 min and from 13.6 to 18.8 °C, respectively. Salts such as CaCl2, CaO, C8H5KO4, and MgSO4 increased the protease activity, while all organic solvents caused its decrease. The results are useful for future studies about ATPS scale-up for enzyme purification and protease application in different industrial processes.

Purification, Characterization, and Application of Alkaline Protease Enzyme from a Locally Isolated Bacillus cereus Strain

Among the microbial enzymes protease and amylase are the most valuable enzymes which have been has diversified applications and used extensively because of their capabilities in the degradation of organic wastes, application in biofuels, agricultural, pharmaceuticals, chemical and biotechnological industries. The aim of the current research work was the purification, characterization and application of alkaline proteases extracted from Bacillus cereus AUST-7. Various concentrations of ammonium sulphate were applied for enzyme precipitation. Sephadex-G 100 was used in FPLC system for separation of protease from other proteins. SDS-PAGE was used to measure the molecular weight of required alkaline protease. Relative activities were determined against different pH, temperature, and incubation period to measure the enzymes activity. Stability of pH, temperature and various metal ions and inhibiter were also studied. Purified enzymes were applied on the goat skin to explore the dehairing efficacy. A 6.5 purification fold and 1163.50 U/mg of specific activity were obtained at 70% saturation and 35. 91 purification fold and 8902 U/mg of specific activity were observed after FPLC separation. The 35 kDa molecular size of protease enzyme was exhibited on the SDS-PAGE. The purified enzyme was stable at pH 10, temperature 55 °C and 35 min of incubation period. The purified enzyme was found to be stable at pH 8–11, thermo-stability at 50 °C and phenyl methyl sulphonyl fluoride (PMSF) and di-isopropyl fluorophosphates (DFP) inhibited the enzyme activity. The enzyme has good potential as dehairing agent in leather industries.

Characterization of redox and salinity-tolerant alkaline protease from Bacillus halotolerans strain DS5

Bacillus halotolerans DS5 was isolated and identified as a halophilic microbe according to 16S rRNA analysis and the physical and chemical indices of the strain. A new alkaline protease (designated as prot DS5) from Bacillus halotolerans DS5 was produced, purified, and characterized. After 12 h incubation in the medium with 1% dextrin, 0.5% NaCl, 2% soluble starch, and 1% yeast extract (pH 7.0), it could reach the maximum enzyme activity (279.74 U/ml). The prot DS5 was stable in the pH range of 6.0–12.0 and the temperature range of 40–60°C, with maximal hydrolytic activities at pH 9 and at 50°C. In the presence of Ca2+, Mn2+, Ba2+, Mg2+, and Fe3+, protease activity was enhanced. The prot DS5 was maintained highly stable in NaCl (up to 2.5 mol/L), reducing and oxidizing agents. The prot DS5 also exhibited compatibility in other detergent ingredients, such as non-ionic and anionic surfactants. These properties of prot DS5 make this enzyme suitable for various industrial applications (e.g., detergents and leather).

A novel strain of Stenotrophomonas acidaminiphila produces thermostable alkaline peptidase on agro-industrial wastes: process optimization, kinetic modeling and scale-up

Bacterial alkaline peptidases, especially from Bacillus species, occupy the frontline in global enzyme market, albeit with poor production economics. Here, we report the deployment of response surface methodology approximations to optimize fermentation parameters for enhanced yield of alkaline peptidase by the non-Bacillus bacterium; Stenotrophomonas acidaminiphila. Shake flask production under optimized conditions was scaled up in a 5-L bench-scale bioreactor. Logistic and modified Gompertz models revealed significant fits for biomass formation, total protein, and substrate consumption models. Maximum specific growth rate (µ_max = 0.362 h^-1) of the bacterium in the optimized medium did not differ significantly from those in Luria-Bertani and trypticase soy broths. The aqueous two-phase system-purified 45.7 kDa alkaline protease retained 83% activity which improved with increasing sodium dodecyl sulfate concentration thus highlighting potential laundry application. Maximum enzyme activity occurred at 75ºC and pH 10.5 but was inhibited by 5 mM phenyl-methyl-sulfonyl fluoride suggesting a serine-protease nature.

Production, Optimization, and Partial Purification of Alkali-Thermotolerant Proteases from Newly Isolated Bacillus subtilis S1 and Bacillus amyloliquefaciens KSM12

Proteases that can remain active under extreme conditions such as high temperature, pH, and salt concentration are widely applicable in the commercial sector. The majority of the proteases are rendered useless under harsh conditions in industries. Therefore, there is a need to search for new proteases that can tolerate and function in harsh conditions, thus improving their commercial value. In this study, 142 bacterial isolates were isolated from diverse alkaline soil habitats. The two highest protease-producing bacterial isolates were identified as Bacillus subtilis S1 and Bacillus amyloliquefaciens KSM12, respectively, based on 16S rRNA sequencing. Optimal protease production was detected at pH 8, 37 °C, 48 h, 5% (w/v) NaCl for Bacillus subtilis S1 (99.8 U/mL) and pH 9, 37 °C, 72 h, 10% (w/v) NaCl for Bacillus amyloliquefaciens KSM12 (94.6 U/mL). The molecular weight of these partially purified proteases was then assessed on SDS-PAGE (17 kDa for Bacillus subtilis S1 and 65 kDa for Bacillus amyloliquefaciens KSM12), respectively. The maximum protease activity for Bacillus subtilis S1 was detected at pH 8, 40 °C, and for Bacillus amyloliquefaciens KSM12 at pH 9, 60 °C. These results suggest that the proteases secreted by Bacillus subtilis S1 and Bacillus amyloliquefaciens KSM12 are suitable for industries working in a highly alkaline environment.

Novel Feather Degrading Keratinases from Bacillus cereus Group: Biochemical, Genetic and Bioinformatics Analysis

In this study, five keratinolytic bacteria were isolated from poultry farm waste of Eastern Province, Saudi Arabia. The highest keratinase activity was obtained at 40–45 °C, pH 8–9, feather concentration 0.5–1%, and using white chicken feather as keratin substrate for 72 h. Enhancement of keratinase activity through physical mutagen UV radiation and/or chemical mutagen ethyl methanesulfonate (EMS) resulted in five mutants with 1.51–3.73-fold increased activity over the wild type. When compared with the wild type, scanning electron microscopy validated the mutants’ effectiveness in feather degradation. Bacterial isolates are classified as members of the S8 family peptidase Bacillus cereus group based on sequence analysis of the 16S rRNA and keratinase genes. Interestingly, keratinase KerS gene shared 95.5–100% identity to keratinase, thermitase alkaline serine protease, and thermophilic serine protease of the B. cereus group. D₁₃₇N substitution was observed in the keratinase KerS gene of the mutant strain S13 (KerS13uv+ems), and also seven substitution variations in KerS26 and KerS26uv of strain S26 and its mutant S26uv. Functional analysis revealed that the subtilisin-like serine protease domain containing the Asp/His/Ser catalytic triad of KerS gene was not affected by the predicted substitutions. Prediction of physicochemical properties of KerS gene showed instability index between 17.5–19.3 and aliphatic index between 74.7–75.7, which imply keratinase stability and significant thermostability. The docking studies revealed the impact of substitutions on the superimposed structure and an increase in binding of mutant D₁₃₇N of KerS13uv+ems (affinity: −7.17; S score: −6.54 kcal/mol) and seven mutants of KerS26uv (affinity: −7.43; S score: −7.17 kcal/mol) compared to the wild predicted structure (affinity: −6.57; S score: −6.68 kcal/mol). Together, the keratinolytic activity, similarity to thermostable keratinases, and binding affinity suggest that keratinases KerS13uv+ems and KerS26uv could be used for feather processing in the industry.

In vitro and in silico characterization of alkaline serine protease from Bacillus subtilis D9 recovered from Saudi Arabia

In this study, we have isolated and characterized proteolytic soil bacteria and their alkaline protease. Based on 16S rRNA sequence analysis, 12 isolates with the highest protease activity were classified as B. subtilis and B. cereus groups. B. subtilis D9 isolate showing the highest protease activity was selected for in vitro and in silico analysis for its ِِAKD9 protease. The enzyme has a molecular mass of 48 kDa, exhibiting optimal activity at 50 °C pH 9.5, and showed high stability till 65 °C and pH 8–11 for 1 h. Fe³⁺‏ stimulated, but Zn²⁺ and Hg²⁺ strongly inhibited the protease activity. Also, the maximum inhibition with PMSF indicated serine protease-type of AKD9 protease. AkD9 alkaline serine protease gene showed high sequence similarity and close phylogenetic relationship with AprX serine protease of B. subtilis isolates. Functional prediction of AKD9 resulted in the detection of subtilase domain, peptidase_S8 family, and subtilase active sites. Moreover, prediction of physicochemical properties indicated that AKD9 serine protease is hydrophilic, thermostable, and alkali-halo stable. Secondary structure prediction revealed the dominance of the coils enhances AKD9 activity and stability under saline and alkaline conditions. Based on molecular docking, AKD9 showed very promising binding affinities towards casein substrate with expected intrinsic proteolytic activities matching our obtained in vitro results. In conclusion, AKD9 alkaline serine protease seems to be a significant candidate for industrial applications because of its stability, hydrophilicity, enhanced thermostability, and alkali-halo stability.

Microbial proteases: ubiquitous enzymes with innumerable uses

Proteases are ubiquitous enzymes, having significant physiological roles in both synthesis and degradation. The use of microbial proteases in food fermentation is an age-old process, which is today being successfully employed in other industries with the advent of ‘omics’ era and innovations in genetic and protein engineering approaches. Proteases have found application in industries besides food, like leather, textiles, detergent, waste management, agriculture, animal husbandry, cosmetics, and pharmaceutics. With the rising demands and applications, researchers are exploring various approaches to discover, redesign, or artificially synthesize enzymes with better applicability in the industrial processes. These enzymes offer a sustainable and environmentally safer option, besides possessing economic and commercial value. Various bacterial and fungal proteases are already holding a commercially pivotal role in the industry. The current review summarizes the characteristics and types of proteases, microbial source, their current and prospective applications in various industries, and future challenges. Promoting these biocatalysts will prove significant in betterment of the modern world.