Purification, biochemical, and molecular characterization of novel protease from Bacillus licheniformis strain K7A

Purification, characterization, optimization, and docking simulation of alkaline protease produced by Brevibacillus agri SAR25 using fish wastes as a substrate

Recycling of protein-rich environmental wastes and obtaining more valuable products from these recycled products is a topic of interest for researchers. This study aims to produce, purify, and characterize the physicochemical and structural properties of the protease enzyme produced from Brevibacillus agri SAR25 using salmon fish waste as substrate and also to evaluate the effect of protease on the chicken feather, enzyme-ligand interactions, and active site surface area. The production of protease was optimum on 50 g/L fish waste, pH 8, 40 °C, 96 h, and 150 rpm. The alkaline protease was isolated using three-phase partitioning (TPP), a straightforward and efficient one-step method for purifying enzymes in industrial applications. TPP achieved a purification efficiency of 115 % with a 3.1-fold increase in concentration. As a result, the molecular weight of the purified protease was determined to be 50 kDa under optimal conditions of pH 9 and 45 °C. The 3D structure of the alkaline protease enzyme with the determined ligands was predicted by homology modeling using UCSF Chimera 1.17.3 software. Tween-20 ligand showed the best binding affinity by hydrogen bonding with amino acids 106 A, Asn 133 A, Gly 198, Asn 226, Glu 232 and hydrophobic interaction with His 135, Leu 283 in the active site of the alkaline protease enzyme, thus leading to the discovery of new semisynthetic enzymes of salmon fish waste. The activity and stability of Brevibacillus agri SAR25 alkaline protease over a wide range of temperatures and pH, and its relatively high stability in the presence of various metal ions, organic solvents, and surfactants indicate that it can be used as a biocatalyst for different industrial applications. This could lead to the creation of new enzymes made from recycled biological materials.

Proteases and keratinases from Bacillus zhangzhouensis MH1: Practical use in detergent, leather, and waste management processes

Microbial proteases and keratinases find extensive application in both the detergent and leather industries, as well as in poultry waste management. In this study, a multifunctional strain MH1 exhibiting proteolytic and keratinolytic activities was newly isolated and identified as Bacillus zhangzhouensis. To improve its stability, the proteolytic extract was spray-dried and the stability was assessed during two years of storage. The enzyme preparation was fully stable up to 20 months of conservation at 4 °C even in the absence of any protective agent, while the enzymatic half-life at room temperature was twenty months using maltodextrin as a protector additive. MH1 was a feather-decomposing strain producing keratinases (95 U/ml) on feather medium. Therefore, the study evaluated the use of these enzymes in the detergent, tannery, and feed processes. Results showed that the sprayed proteases showed high compatibility with commercial liquid and solid detergents and efficiently removed bloodstains at low wash temperatures. They also revealed significant dehairing activity of cow skin without surface damage. While keratinases effectively transformed chicken feathers into keratin hydrolysate with strong antioxidant activity. Therefore, these enzymes could be a green alternative to hazardous chemicals utilized for detergent, leather, and biodegradation of keratinous waste.

Efficient Hydrolysis of Fish Parvalbumin by Marine Bacterial Protease VSP2V-280: Allergen Removal

Parvalbumin is a major allergen in fish. However, there is currently no effective and safe way to remove this allergen from fish. In this study, protease gene VSP2V-280 of marine bacteria Virgibacillus sp. SP2 was cloned and expressed. The protease enzyme showed maximum activity at 50°C and pH 10.0. Ca2+ and Cu2+ promoted the enzyme. The enzyme showed good parvalbumin degradation efficiency in fish. Based on the gel analysis, when 0.3 mg/mL of parvalbumin was incubated with protease VSP2V-280 (30 U/mL) containing 1 mM Ca2+ for 3 h, the parvalbumin removal rate reached 97%. The enzyme was further used for parvalbumin removal from Ctenopharyngodon idella, Pelteobagrus fulvidraco, Parabramis pekinensis, and Carassius auratus. The parvalbumin removal rate reached 93% in 4 h at an enzyme dosage of 72 U/mL. The study showed the potential of VSP2V-280 to remove parvalbumin from aquatic products.

Protein engineering of an alkaline protease from Bacillus licheniformis (BLAP) for efficient and specific chiral resolution of the racemic ethyl tetrahydrofuroate

Enzymatic resolution of ethyl tetrahydrofuroate to produce (S)-2-ethyl tetrahydrofuroate and (R)-2-tetrahydrofuroic acid is a green biomanufacturing strategy. However, enzymatic activity and selectivity are still limiting factors of their industrial applications and development. In previous study, we incidentally found that a Bacillus licheniformis alkaline protease (BLAP), not a lipase, could specifically resolve ethyl tetrahydrofuroate to produce (S)-2-ethyl tetrahydrofuroate and (R)-2-tetrahydrofuroic acid. In this study, the point-saturation-mutation libraries based on the seven amino acid sites (L105, I113, P114, L115, V309, Y310, and M326) were constructed and screened using the molecular docking technology. It was found that activity of the mutant BLAPY310E reached 182.78 U/mL with high stereoselectivity, 3.14 times higher than that of the wild-type BLAP. Further simulated mutation analysis showed that the Y310E mutation increased the distance from the substrate ligand to the binding pocket from 2.3 Å to 4.5 Å, reducing steric hindrance to the active center. Under the optimal conditions and after 3.5 h of reaction catalyzed by BLAPY310E, 200 mM ethyl tetrahydrofuroate was converted to (S)-2-ethyl tetrahydrofuroate and (R)-2-tetrahydrofuroic acid with the ee values of 99.9 % and 68.63 %, respectively. The enantiomeric ratio of BLAPY310E was 105.5, which was 30.23 times higher than that of BLAP. This study advances the comprehension of protease activity and selectivity mechanisms in resolving ester substances and lays a robust foundation for the industrial production of the optically pure (S)-2-ethyl tetrahydrofuroate and (R)-2-tetrahydrofuroic acid via biological enzymatic methods.

New Bacillus paralicheniformis strain with high proteolytic and keratinolytic activity

Bacillus paralicheniformis T7, which exhibits high proteolytic and keratinolytic activities, was isolated from soil in Kazakhstan. Its secreted proteases were thermostable and alkaline, demonstrating maximum activity at 70 °C and pH 9.0. The proteases and keratinases of this strain were sensitive to Ni2+, Co2+, Mn2+, and Cd2+, with Cu2+, Co2+ and Cd2+ negatively affecting keratinolytic activity, and Fe3+ ions have a strong inhibitory effect on proteolytic and keratinolytic activity. Seven proteases were identified in the enzymatic extract of B. paralicheniformis T7: four from the serine peptidase family and three from the metallopeptidase family. The proteases hydrolyzed 1 mg of casein, hemoglobin, gelatin, ovalbumin, bovine serum albumin, or keratin within 15 s to 30 min. The high keratinolytic activity of this strain was confirmed through the degradation of chicken feathers, horns, hooves, wool, and cattle hide. Chicken feathers were hydrolyzed in 4 days, and the degrees of hydrolysis for cattle hide, wool, hoof, and horn after 7 days of cultivation were 97.2, 34.5, 29.6, and 3.6%, respectively. During submerged fermentation with feather medium in a laboratory bioreactor, the strain secreted enzymes with 249.20 ± 7.88 U/mL protease activity after 24 h. Thus, B. paralicheniformis T7 can be used to produce proteolytic and keratinolytic enzymes for application in processing proteinaceous raw materials and keratinous animal waste.

Molecular basis for the increased activity of ZMS-2 serine protease in the presence of metal ions and hydrogen peroxide

Serine proteases are important enzymes widely used in commercial products and industry. Recently, we identified a new serine protease from the desert bacterium Bacillus subtilis ZMS-2 that showed enhanced activity in the presence of Zn2+, Ag+, or H2O2. However, the molecular basis underlying this interesting property is unknown. Here, we report comparative studies between the ZMS-2 protease and its homolog, subtilisin E (SubE), from B. subtilis ATCC 6051. In the absence of Zn2+, Ag+, or H2O2, both enzymes showed the same level of proteolytic activity, but in the presence of Zn2+, Ag+, or H2O2, ZMS-2 displayed increased activity by 22%, 8%, and 14%, whereas SubE showed decreased activity by 16%, 12%, and 9%, respectively. In silico studies showed that both proteins have almost identical amino acid sequences and folding structures, except for two amino acids located in the protruding loops of the proteins. ZMS-2 contains Ser236 and Ser268, whereas SubE contains Thr236 and Thr268. Replacing Ser236 or Ser268 in ZMS-2 with threonine resulted in variants whose activities were not enhanced by Zn2+ or Ag+. However, this single mutation did not affect the enhancement by H2O2. This finding may be used as a basis for engineering better proteases for industrial uses.

Biochemical characterization of immobilized recombinant subtilisin and synthesis and functional characterization of recombinant subtilisin capped silver and zinc oxide nanoparticles

This pioneering research explores the transformative potential of recombinant subtilisin, emphasizing its strategic immobilization and nanoparticle synthesis to elevate both stability and therapeutic efficacy. Achieving an impressive 95.25 % immobilization yield with 3 % alginate composed of sodium along with 0.2 M CaCl2 indicates heightened pH levels and thermal resistance, with optimal action around pH 10 as well as 80 °C temperature. Notably, the Ca-alginate-immobilized subtilisin exhibits exceptional storage longevity and recyclability, affirming its practical viability. Comprehensive analyses of the recombinant subtilisin under diverse conditions underscore its adaptability, reflected in kinetic enhancements with increased Vmax (10.7 ± 15 × 103 U/mg) and decreased Km (0.19 ± 0.3 mM) values post-immobilization using N-Suc-F-A-A-F-pNA. UV-visible spectroscopy confirms the successful capping of nanoparticles made of Ag and ZnO by recombinant subtilisin, imparting profound antibacterial efficacy against diverse organisms and compelling antioxidant properties. Cytotoxicity was detected against the MCF-7 breast cancer line of cells, exhibiting IC50 concentrations at 8.87 as well as 14.52 µg/mL of AgNP as well as ZnONP, correspondingly, indicating promising anticancer potential. Rigorous characterization, including FTIR, SEM-EDS, TGA and AFM robustly validate the properties of the capped nanoparticles. Beyond therapeutic implications, the investigation explores industrial applications, revealing the versatility of recombinant subtilisin in dehairing, blood clot dissolution, biosurfactant activity, and blood stain removal. In summary, this research unfolds the exceptional promise of recombinant subtilisin and its nanoparticles, presenting compelling opportunities for diverse therapeutic applications in medicine. These findings contribute substantively to biotechnology and healthcare and stimulate avenues for further innovation and exploration.

Screening of Bacillus spp. bacterial endophytes for protease production, and application in feather degradation and bio-detergent additive

Research on proteases and secondary metabolites from endophytes is an area that requires attention from researchers. In this study, proteases from Bacillus sp. strain MHSD16 and Bacillus sp. strain MHSD17 endophytes were characterised, and their potential biotechnological applications were investigated. Optimum protease production was achieved when isolates were grown in media containing (g/L): glucose 10g, casein 5g, yeast extract 5g, KH2PO4 2g, Na2CO3 10g at pH 9. The crude protease extracts were active in alkaline environments, thus referred to as alkaline proteases with optimal pH of 10. Additionally, Bacillus sp. strain MHSD 16 and Bacillus sp. strain MHSD17 proteases were active at high temperatures, with optimum enzyme activity at 50 °C. Thermostability profiles of these proteases showed that the enzymes were highly stable between (40-60 °C), maintaining over 85 % stability after 120 min incubation at 60 °C. Furthermore, the enzymes were stable and compatible with various household and laundry detergents. In the presence of commercial laundry detergent, OMO® 68 % and 72 % activity was retained for Bacillus sp. strain MHSD16 and Bacillus sp. strain MHSD17, respectively, while 67 % and 68 % activity were retained in the presence of Sunlight®. The potential application for use in detergents was investigated through the removal of blood stains with the crude alkaline extracts displaying efficient stain removal abilities. Feather degradation was also investigated and Bacillus sp. MHSD17 exhibited feather keratin degrading properties more effectively than Bacillus sp. MHSD16.

Heterologous expression and characterization of an M4 family extracellular metalloprotease for detergent application

Proteolytic enzymes stand out as the most widely employed category utilized in manufacturing industry. A new protease was separated from Planococcus sp.11815 strain and named as nprS-15615 in this research. The gene of this protease has not been reported, and its enzymatic properties have been studied for the first time. To enhance enzyme production, the Planococcus sp. protease gene was expressed in Bacillus licheniformis 2709. The expression level of nprS-15615 was observed under the control of regulatory elements PaprE. nprS-15615 protease activity reached 1186.24±32.87 U/mL after 48 hours of cultivation in shake flasks which was nearly four times the output of the original bacteria (291.38±25.73U/mL). The optimum temperature and pH of the recombinant protease were 30 ℃ and 8.0, respectively.The enzyme exhibited the highest capacity for hydrolyzing casein and demonstrated resilience towards a NaCl concentration of 10.0% (wt/v). Furthermore, in the presence of 0.5% surfactants, the recombinant protease activity can maintain above 75%, and with the existence of 0.5% liquid detergents, there was basically no loss of enzyme activity which indicated that nprS-15615 had good compatibility with surfactants and liquid detergents. In addition, npS-15615 performed well in the washing experiment, and the washing effect at 20 ℃ can be significantly improved by adding crude enzyme solution in the washing process.

Alkaline Thermo- and Oxidant-Stable Protease from Bacillus pumilus Strain TNP93: Laundry Detergent Formulations

The study aims to produce a detergent-compatible and alkaline thermophilic protease from a Bacillus strain and to investigate its usability as a detergent bio-additive. The protease-producing bacterium was identified as Bacillus pumilus strain TNP93 according to the 16S rRNA sequence. The bacterium optimally synthesized the protease at 40 °C and pH 10 in 40 h. The raw protease displayed its optimum activity at pH 10 and 60 °C and its stability between pH 6-13 and 30-100 °C for 24 h. The molecular mass of the proteolytic band was estimated to be about 85 kDa. The protease was not inhibited by any of the metal ions used (Ba2+, Ca2+, Co2+, Cu2+, Mg2+, Mn2+, Zn2+). 97 and 90% of its original activity with 5 mM PMSF and EDTA remained. The activity was measured as 84, 124, and 95%, respectively, in the presence of 1% concentrations of Tween 20, Tween 80, and Triton X-100. In addition, all of its activity was preserved when the enzyme was exposed to 5% H2O2. The end products of casein were detected as tyrosine, aspartic acid, glycine, and cysteine by thin-layer chromatography. Considering the wash performance analysis, the mix of 1% commercial detergent and enzyme almost removed all of the protein-based stains (blood and egg yolk albumin). These remarkable findings indicate that the alkaline, thermo-, and oxidant-stable TNP93 protease is a valuable candidate for usage as a biological additive in various laundry detergents.

Microbial proteases and their applications

Proteases (proteinases or peptidases) are a class of hydrolases that cleave peptide chains in proteins. Endopeptidases are a type of protease that hydrolyze the internal peptide bonds of proteins, forming shorter peptides; exopeptidases hydrolyze the terminal peptide bonds from the C-terminal or N-terminal, forming free amino acids. Microbial proteases are a popular instrument in many industrial applications. In this review, the classification, detection, identification, and sources of microbial proteases are systematically introduced, as well as their applications in food, detergents, waste treatment, and biotechnology processes in the industry fields. In addition, recent studies on techniques used to express heterologous microbial proteases are summarized to describe the process of studying proteases. Finally, future developmental trends for microbial proteases are discussed.

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.

Bacillus Swezeyi B2 Strain: A Novel Alkaliphilic Bacterium Producer of Alkaline-, Thermal, Oxidant-, and Surfactant-Stable Protease, Extremely Efficient in Detergency

Proteolytic enzymes that are currently used to meet industrial demand are usually derived from Bacillus species. They find multiple technical applications, particularly they have been increasingly used as a key bio-additive in detergents. In this study, a novel alkalophilic bacterium was isolated from contaminated soil, exhibiting 1400 U/ml proteolytic activity, and identified as Bacillus swezeyi B2. The crude enzyme likely contained a single extracellular protease. This enzyme revealed optimum activity at pH 10 and 70 °C and was highly alkaline thermostable (7-12.5) and up to 70 °C. The protease activity was completely inhibited by Phenylmethylsulfonyl fluoride (PMSF) suggesting that it belongs to the serine protease group. It was highly stable in the presence of the strong anionic surfactant (SDS) and oxidizing agents (H₂O₂). The supernatant was lyophilized and showed high storage stability retaining 100% of its original activity after one year of conservation at 4 °C. The lyophilized product was evaluated for its detergent efficacy, it revealed excellent compatibility with various laundry detergents keeping its full original activity after incubation for 1 h with seven solid and liquid commercial detergents and it effectively removed chocolate stains at low washing temperature (40 °C) and low supplementation level (125 U/ml). The features of this single alkaline and thermotolerant protease, stable toward surfactants, oxidizing agents, and commercial detergents with stain removal efficacy support its ideal choice for supplementation in detergent formulations.

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).

Bacillus halotolerans KKD1 induces physiological, metabolic and molecular reprogramming in wheat under saline condition

Salt stress decreases plant growth and is a major threat to crop yields worldwide. The present study aimed to alleviate salt stress in plants by inoculation with halophilic plant growth-promoting rhizobacteria (PGPR) isolated from an extreme environment in the Qinghai-Tibetan Plateau. Wheat plants inoculated with Bacillus halotolerans KKD1 showed increased seedling morphological parameters and physiological indexes. The expression of wheat genes directly involved in plant growth was upregulated in the presence of KKD1, as shown by real-time quantitative PCR (RT-qPCR) analysis. The metabolism of phytohormones, such as 6-benzylaminopurine and gibberellic acid were also enhanced. Mining of the KKD1 genome corroborated its potential plant growth promotion (PGP) and biocontrol properties. Moreover, KKD1 was able to support plant growth under salt stress by inducing a stress response in wheat by modulating phytohormone levels, regulating lipid peroxidation, accumulating betaine, and excluding Na⁺. In addition, KKD1 positively affected the soil nitrogen content, soil phosphorus content and soil pH. Our findings indicated that KKD1 is a promising candidate for encouraging wheat plant growth under saline conditions.

Production and characterization of a new detergent-stable keratinase expressed by Pedobacter sp. 3.14.7, a novel Antarctic psychrotolerant keratin-degrading bacterium

BACKGROUND

Antarctica is one of the harshest environments in the world. Despite this fact, it has been colonized by microorganisms, which had to develop different adaptations in order to survive. By studying their enzymes, we can harness these adaptations in order to use them in various industrial processes. Keratinases (E.C. 3.4.99.11) are characterized by their robustness in withstanding extreme conditions and, along with other enzymes, are commonly added to laundry detergents, which makes their study of industrial interest.

RESULTS

In this work, a novel keratinase producer, Pedobacter sp. 3.14.7 (MF 347939.1), isolated from Antarctic birds' nests, was identified. This psychrotolerant isolate displays a typical psychrotolerant growth pattern, with an optimal temperature of 20 °C (μmax=0.23 h^-1). After 238 h, maximum proteolytic (22.00 ± 1.17 U ml^-1) and keratinolytic (33.04 ± 1.09 U ml^-1) activities were achieved with a feather sample conversion of approximately 85%. The keratinase present in crude extract was characterized as a metalloprotease with a molecular weight of 25 kDa, stable in a wide range of pH, with an optimum pH of 7.5. Optimum temperature was 55 °C. Wash performance at 20 °C using this crude extract could remove completely blood stain from cotton cloth.

CONCLUSION

We report a new keratinolytic bacteria from maritime Antarctica. Among its biochemical characteristics, its stability in the presence of different detergents and bleaching agents and its wash performance showed promising results regarding its potential use as a laundry detergent additive.

Production of protease with Bacillus megaterium DSM32: Partial characterisation of the enzyme and modelling of the production

Proteases hold an important position in today's world commercial enzyme market. Among various microbial producer genera, Bacillus is leading the commercial protease production. However, industry is still actively looking for new microbial protease producers with distinctive properties. Therefore, this study was undertaken for the evaluation of protease production by Bacillus megaterium DSM 32 strain in terms of its protease productivity, calculation of various production kinetics, partial characterisation of the enzyme, and modelling the protease production process. As results, the highest protease activity, specific cellular protease production rate, and protease productivity were calculated as 255.42 U mL−1, 36.2514 U g−1, and 16.1313 U mL−1 h−1, respectively, in shake flask fermentations. Partial characterisation studies showed that the enzyme has 45 °C and pH 8 as optimum working conditions, and its activity increased by 24% with the addition of 5 mM Mn+2 to the reaction medium. Additionally, the enzyme showed high stability and kept almost full activity in a cell-free medium for 20 days at 4 °C. Furthermore, modified Gompertz model provided the best fit in describing protease production with the lowest error and high fit values.

Identification of a thermophilic protease-producing strain and its application in solid-state fermentation of soybean meal

BACKGROUND

Thermophiles can thrive at 50-80 °C and produce some enzymes with special promise for biocatalysis. A thermophilic protease-producing strain YYC4 was isolated from Yunyan cigarette and employed in solid-state fermentation (SSF) of unsterilized soybean meal (SBM).

RESULTS

The isolate was identified as Bacillus licheniformis based on appearance of colonies, microscopic observation and 16S rDNA sequencing. After SSF, soluble and crude protein contents in SBM increased from 49.24 to 185.73 g kg-1 and from 404.18 to 479.46 g kg-1 , respectively, under the fermentation conditions of 107  cfu g-1 inoculation of strain YYC4, 1:1.8 (g mL-1 ) SBM to distilled water, 1.2 g kg-1 magnesium sulphate addition, 55 °C and 48 h. During fermentation, pH of the medium increased from 6.30 to 9.09 and protease activity especially neutral protease increased significantly from 13.5 to 181.31 U g-1 . Meanwhile, trypsin inhibitor (TI) activity was decreased from 8.19 to 3.19 mg g-1 . The safety of fermented SBM (FSBM) was verified by acute toxicity animal experiment. Analysis of microbial community in FSBM showed that Bacillus licheniformis YYC4 as a dominant strain inhibited most of the other microorganisms pre-existing in the materials during fermentation.

CONCLUSION

Increments of soluble and crude protein by 277.19% and 18.63% and decrement of harmful TI by 61.05% in SBM were achieved using thermophilic SSF by Bacillus licheniformis YYC4, providing a basis for the application of thermophiles in fermentation industry in an environmentally friendly and energy-saving way. © 2021 Society of Chemical Industry.

Production of subtilisin proteases in bacteria and yeast

In this review, we discuss the progress in the study and modification of subtilisin proteases. Despite longstanding applications of microbial proteases and a large number of research papers, the search for new protease genes, the construction of producer strains, and the development of methods for their practical application are still relevant and important, judging by the number of citations of the research articles on proteases and their microbial producers. This enzyme class represents the largest share of the industrial production of proteins worldwide. This situation can explain the high level of interest in these enzymes and points to the high importance of designing domestic technologies for their manufacture. The review covers subtilisin classification, the history of their discovery, and subsequent research on the optimization of their properties. An overview of the classes of subtilisin proteases and related enzymes is provided too. There is a discussion about the problems with the search for (and selection of) subtilases from natural strains of various microorganisms, approaches to (and specifics of) their modification, as well as the relevant genetic engineering techniques. Details are provided on the methods for expression optimization of industrial subtilases of various strains: the details of the most important parameters of cultivation, i.e., composition of the media, culture duration, and the influence of temperature and pH. Also presented are the results of the latest studies on cultivation techniques: submerged and solid-state fermentation. From the literature data reviewed, we can conclude that native enzymes (i.e., those obtained from natural sources) currently hardly have any practical applications because of the decisive advantages of the enzymes modified by genetic engineering and having better properties: e.g., thermal stability, general resistance to detergents and specific resistance to various oxidants, high activity in various temperature ranges, independence from metal ions, and stability in the absence of calcium. The vast majority of subtilisin proteases are expressed in producer strains belonging to different species of the genus Bacillus. Meanwhile, there is an effort to adapt the expression of these enzymes to other microbes, in particular species of the yeast Pichia pastoris.

Characterization of a salt-resistant fibrinolytic protease of Bacillus licheniformis HJ4 isolated from Hwangseokae jeotgal, a traditional Korean fermented seafood

Bacillus licheniformis HJ4 showing strong fibrinolytic activity was isolated from Hwangseokae jeotgal. aprEHJ4, a major fibrinolytic gene, was cloned by PCR, and an ORF consisting of 379 amino acids was located. The mature enzyme was expected to be 27 kDa in size after processing, but a 24-kDa protein was observed by SDS-PAGE and fibrin zymography, indicating additional processing. RT-qPCR showed that expression level of aprEHJ4 in culture with 0% salt (control) was the highest followed by culture with 8% salt (89.7% of control) and 5% salt (74.2%) at 84 h. The expression level in culture with 15% salt was 46.9%. The results matched with the fibrinolytic activity measurements of cultures and indicated that AprEHJ4 maintained significant activity in the presence of salt up to 15% (w/v). AprEHJ4 was overproduced in Escherichia coli, and mature 27 kDa protein was purified after in vitro renaturation. The optimum pH and temperature of AprEHJ4 were pH 8 and 40 ℃, respectively.

Microbial alkaline serine proteases: Production, properties and applications

Proteolytic enzymes hold a pivotal position in numerous industrial processes where hydrolysis of protein molecules is required under precise conditions. The emerging trend of biotechnological applications in recent years has witnessed a renewed interest in alkaline serine proteases extending their utility in detergent, leather, textile, food and pharmaceutical industries. A variety of microorganisms have been reported to produce alkaline serine proteases on a large scale, however, extensive research to find an alkaline serine protease with desirable characteristics such as significant catalytic efficiency, expanded stability and broad substrate specificity is still ongoing. Although submerged fermentation dominates the commercial enzyme production, recent reports have emphasized on solid state fermentation technology which can reduce major cost associated with the enzyme production. In the present review, recent research on alkaline serine proteases along with their novel properties and production using solid state fermentation have been discussed.

Revisiting the scope and applications of food enzymes from extremophiles

Microorganisms from extreme environments tend to undergo various adaptations due to environmental conditions such as extreme pH, temperature, salinity, heavy metals, and solvents. Thus, they produce enzymes with unique properties and high specificity, making them useful industrially, particularly in the food industries. Despite these enzymes' remarkable properties, only a few instances can be reported for actual exploitation in the food industry. This review's objectives are to highlight the properties of these enzymes and their prospects in the food industry. First, an introduction to extremophilic organisms is presented, followed by the categories and application of food enzymes from extremophiles. Then, the unique structural features of extremozymes are shown. This review also covers the prospective applications of extremozymes in the food industry in a broader sense, including degradation of toxins, deconstruction of polymers into monomers, and catalysis of multistep processes. Finally, the challenges in bioprocessing of extremozymes and applications in food are presented. PRACTICAL APPLICATIONS: Enzymes are important players in food processing and preservation. Extremozymes, by their nature, are ideal for a broad range of food processing applications, particularly those that require process conditions of extreme pH, temperature, and salinity. As the global food industry grows, so too will grow the need to research and develop food products that are diverse, safe, healthy, and nutritious. There is also the need to produce food in a sustainable way that generates less waste or maximizes waste valorization. We anticipate that extremozymes can meet some of the research and development needs of the food industry.

Enhanced catalytic activity of Bacillus aryabhattai P1 protease by modulation with nanoactivator

In the developing area of modern nanobiotechnology, the research is being focused on enhancement of catalytic performance in terms of efficiency and stability of enzymes to fulfill the industrial demand. In the context of this interdisciplinary era, we isolated and identified alkaline protease producer Bacillus aryabhattai P1 by polyphasic approach and then followed one variable at a time approach to optimize protease production from P1. The modified components of fermentation medium (g/L) were wheat bran 10, soybean flour 10, yeast extract 5, NaCl 10, KH₂PO₄ 1, K₂HPO₄ 1 and MgSO₄·7H₂O 0.2 (pH 9). The optimum alkaline protease production from P1 was recorded 75 ± 3 U/mg at 35 °C and pH 9 after 96 h of fermentation period. Molecular weight of partially purified P1 alkaline protease was 26 KDa as revealed by SDS-PAGE. Calcium based nanoceramic material was prepared by wet chemical precipitation method and doped in native P1 protease for catalytic activity enhancement. Catalytic activity of modified P1 protease was attained by nanoactivator mediated modulation was more by 5.58 fold at pH 10 and 30 °C temperature. The nanoceramic material named as nanoactivator, with grain size of 40–60 nm was suitable to redesign the active site of P1 protease. Such types of modified proteases can be used in different nanobiotechnological applications.

Biochemical Properties of a Partially Purified Protease from Bacillus sp. CL18 and Its Use to Obtain Bioactive Soy Protein Hydrolysates

Microbial proteases are relevant biocatalysts with diverse applications. Production of protein hydrolysates is recently focused, since they might display biological activities. Therefore, the extracellular protease from Bacillus sp. CL18 was partially purified through ammonium sulfate precipitation (25-50% saturation) and gel filtration chromatography, with a 60.7-fold purification (40,593 U/mg protein) and 21.3% recovery. The partially purified protease (PPP) was characterized as a serine protease, with optimal activity at 51-59 °C and pH 7.4-8.8 and low thermal stability. Thermal inactivation followed first-order kinetics. PPP depended on Ca²⁺ for higher thermal stability, depicted by increases in half-lives (t_1/2), activation energy (E_a), and free energy (ΔG^#) for kinetic inactivation. PPP preferentially hydrolyzed casein > soy protein isolate (SPI) >>> keratinous materials. SPI hydrolysis by PPP was further investigated, and the obtained hydrolysates exhibited increased in vitro bioactivities. Hydrolysates displayed antioxidant capacities through the scavenging of synthetic organic radicals and Fe³⁺-reducing ability. In addition, hydrolysates inhibited the activities of dipeptidyl peptidase IV (DPP IV) and angiotensin-converting enzyme (ACE), suggesting antidiabetic and antihypertensive potentials, respectively. From its biochemical properties, PPP might be used to produce protein hydrolysates with multifunctional bioactivities. Both PPP and SPI hydrolysates can find applications in food biotechnology.

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.

Identification of a novel protease from the thermophilic Anoxybacillus kamchatkensis M1V and its application as laundry detergent additive

A thermostable extracellular alkaline protease (called SAPA) was produced (4600 U/mL) by Anoxybacillus kamchatkensis M1V, purified to homogeneity, and biochemically characterized. SAPA is a monomer with a molecular mass of 28 kDa estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), Native-PAGE, casein-zymography, and size exclusion using high performance liquid chromatography (HPLC). The sequence of its NH₂-terminal amino-acid residues showed high homology with those of Bacillus proteases. The SAPA irreversible inhibition by diiodopropyl fluorophosphates (DFP) and phenylmethanesulfonyl fluoride (PMSF) confirmed its belonging to the serine proteases family. Optimal activity of SAPA was at pH 11 and 70 °C. The sapA gene was cloned and expressed in the extracellular fraction of E. coli. The highest sequence identity value (95%) of SAPA was obtained with peptidase S8 from Bacillus subtilis WT 168, but with 16 amino-acids of difference. The biochemical characteristics of the purified recombinant extracellular enzyme (called rSAPA) were analogous to those of native SAPA. Interestingly, rSAPA exhibit a degree of hydrolysis that were 1.24 and 2.6 than SAPB from Bacillus pumilus CBS and subtilisin A from Bacillus licheniformis, respectively. Furthermore, rSAPA showed a high detergent compatibility and an outstanding stain removal capacity compared to commercial enzymes: savinase™ 16L, type EX and alcalase™ Ultra 2.5 L.

A novel thiol-dependent serine protease from Neocosmospora sp. N1

Alkaline proteases have several industrial applications. In the present study, newly isolated Neocosmospora sp. N1 was screened as hyper producer of serine protease. A multimeric protease of the fungus was purified to homogeneity till 96.78 fold purification with 22.51% recovery. The homogeneity of purified enzyme was checked by native PAGE and its molecular weight was found to be 198.03 kDa by MALDI-TOF. On SDS-PAGE analysis, enzyme was found to be a hetero oligomer of 17.66 kDa and 20.89 kDa subunits. The purified enzyme showed maximum activity with casein as substrate at 60 °C and pH 8.5. The K_m and V_max values were found to be 0.015 mg/ml and 454.45 U/ml, respectively. The enzyme was completely inhibited by PMSF, while the activity was 40% enhanced using β-mercaptoethanol, suggesting that it is a thiol-dependent serine protease. The purified protease was active over an alkaline pH range from 7 to 12 and temperatures from 20 °C to 60 °C. The enzyme exhibited excellent stability, almost 100% towards organic solvents such as toluene, benzene and hexane, surfactants such as Triton X-100, Tween-20, Tween-80 and SDS, as well as commercial detergents. The significant properties of purified enzyme assure that it could be a potential candidate for commercial purposes.

Heterologous expression and characterization of a novel subtilisin-like protease from a thermophilic Thermus thermophilus HB8

Subtilisins are a family of serine proteases used widely throughout the detergent, leather and food industries, with the identification and development of new enzymes holding much potential value. Thermus thermophilus HB8 was examined for serine proteases and found TTHA0724 gene. Sequence analysis of this putative serine protease placed it within the subtilisin family. To obtain active T. thermophilus HB8 subtilisins, three genes encoding prepro-subtilisin, pro-subtilisin and mature-subtilisin were cloned and expressed in Escherichia coli Transetta (DE3). Although direct expression of the mature-subtilisin gene was found to produce inactive inclusion bodies, expression of the pro-subtilisin gene resulted in active mature-subtilisin, indicating that the pro-sequence of translated pro-subtilisin underwent autoproteolysis. The resulting mature-subtilisin exhibited maximal activity between 65 and 85 °C at pH 7.5. The mature-subtilisin showed good stability, maintaining 50% activity after 48 h at 75 °C and >78% activity across the pH range 5.0-9.5. Furthermore, the mature-subtilisin demonstrated broad substrate specificity, with no requirement for the presence of metal ions which are essential for other subtilisin enzymes. Despite this Cu²⁺ was able to increase enzyme activity, while Ca²⁺ partially inhibited the activity. These properties suggest that T. thermophilus HB8 mature-subtilisin has potential value in its application in many industries.

Purification and biochemical characterization of a novel thermostable protease from the oyster mushroom Pleurotus sajor-caju strain CTM10057 with industrial interest

BACKGROUND

Proteases are hydrolytic enzymes that catalyze peptide linkage cleavage reactions at the level of proteins and peptides with different degrees of specificity. This group draws the attention of industry. More than one protease in three is a serine protease. Classically, they are active at neutral to alkaline pH. The serine proteases are researched for industrial uses, especially detergents. They are the most commercially available enzyme group in the world market. Overall, fungi produced extracellular proteases, easily separated from mycelium by filtration.

RESULTS

A new basidiomycete fungus CTM10057, a hyperproducer of a novel protease (10,500 U/mL), was identified as Pleurotus sajor-caju (oyster mushroom). The enzyme, called SPPS, was purified to homogeneity by heat-treatment (80 °C for 20 min) followed by ammonium sulfate precipitation (35-55%)-dialysis, then UNO Q-6 FPLC ion-exchange chromatography and finally HPLC-ZORBAX PSM 300 HPSEC gel filtration chromatography, and submitted to biochemical characterization assays. The molecular mass was estimated to be 65 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), Native-PAGE, casein-zymography, and size exclusion by HPLC. A high homology with mushroom proteases was displayed by the first 26 amino-acid residues of the NH2-terminal aminoacid sequence. Phenylmethanesulfonyl fluoride (PMSF) and diiodopropyl fluorophosphates (DFP) strongly inhibit SPPS, revealing that it is a member of the serine-proteases family. The pH and temperature optima were 9.5 and 70 °C, respectively. Interestingly, SPPS possesses the most elevated hydrolysis level and catalytic efficiency in comparison with SPTC, Flavourzyme® 500 L, and Thermolysin type X proteases. More remarkably, a high tolerance towards organic solvent tolerance was exhibited by SPPS, together with considerable detergent stability compared to the commercial proteases Thermolysin type X and Flavourzyme® 500 L, respectively.

CONCLUSIONS

This proves the excellent proprieties characterizing SPPS, making it a potential candidate for industrial applications especially detergent formulations.

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.

Cloning, expression and characterization of a novel alkaline serine protease gene from native Iranian Bacillus sp.; a producer of protease for use in livestock

The use of proteases in the last decade has been welcomed in livestock and poultry industries and has led to significant results such as improved feed conversion ratio, weight gain and increased growth performance. In the present study, isolation and identification of a novel alkaline protease from Iranian Bacillus species was performed in order to use in livestock feed. After primary isolation of bacteria from soil samples of rice fields and early detection of bacterial genus, the zymogram plate was performed for evaluation of production extracellular proteases. Of the 11 strains producing protease, one strain that produced more enzymes was selected to continue the work. Characterization of alkaline protease was done using specific enzyme assays. To confirm the genus of isolates as well as to identify the species close to, molecular analysis of 16S rRNA gene sequence was done. After that, bioinformatics analysis carried out in NCBI database for searching bacterial alkaline proteases gene sequences. The primer designed based on gene homology of close species for extraction of alkaline protease gene. The results showed that the enzyme extract had the highest activity at pH 9.0 and 50 °C. The 16S rRNA gene sequence was submitted for the strain called Bacillus sp. RAM on the NCBI site. According to the results of the phylogenetic tree, the bacterium was belonged to Bacillus genus and Bacillus sp. RAM was close to Thuringiensis C405. The isolated alkaline protease gene successfully cloned in pET28a and transferred to the expression host E.coli BL21. The expression of the protease gene was evaluated by SDS-PAGE electrophoresis. The induced recombinant cells expressed the protease and revealed molecular weight band of about 38 kDa. According to the enzyme properties, this alkaline protease can useful for application in animal industry.

A Tropical Composting Operation Unit at São Paulo Zoo as a Source of Bacterial Proteolytic Enzymes

Composting operation systems are valuable sources of microorganisms and enzymes. This work reports the assessment of proteolytic enzymes from cultivable bacteria isolated from a composting facility of the São Paulo Zoo Park (SPZPF), São Paulo, Brazil. Three hundred bacterial isolates were obtained and identified based on 16S rRNA gene as belonging to 13 different genera. The most common genus among the isolates was Bacillus (67%); some of which show high proteolytic activity in their culture media. Biochemical assays of hydrolytic activities using FRET peptides as substrates allowed the characterization of a repertoire of serine proteases and metalloproteases with different molecular weights secreted by Bacillus strains isolated from composting. Furthermore, thermostable serine and metalloproteases were detected in the composting leachate, which might be of interest for industrial applications.