Purification, biochemical characterization and structural modeling of a potential htrA-like serine protease from Bacillus subtilis DR8806

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.

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.

Production, optimization, and purification of alkaline thermotolerant protease from newly isolated Phalaris minor seeds

The present work aims to purify and perform a preliminary analysis on a thermostable serine alkaline protease from a recently identified P. minor. The enzyme was purified 2.7-fold with a 12.4 % recovery using Sephadex G-100 chromatography, DEAE-cellulose, and ammonium sulphate precipitation. The isolated enzyme has a specific activity of 473 U/mg. The purified protease had a molecular mass of 29 kDa, and just one band was seen, which matched the band obtained using SDS-PAGE. High thermostability was demonstrated by the enzymes, which had half-lives of 31.79 and 6.0 min (a 5.3-fold improvement), enthalpies of denaturation (ΔH°) of 119.53 and 119.35 KJ mol^-1, entropies of denaturation (ΔS°) of 32.96 and 41.11 J/mol·K, and free energies of denaturation (ΔG°) of 108.87 and 105.58 KJ mol^-1 for the protease enzyme. Studies on the folding and stability of alkaline proteases are important since their use in biotechnology requires that they operate in settings of extreme pH and temperature. According to the kinetic and thermodynamic properties, the protease produced by P. minor is superior to that produced by other sources and previously described plants, and it might find utility in a variety of industrial fields.

Marine enzymes: Classification and application in various industries

Oceans are regarded as a plentiful and sustainable source of biological compounds. Enzymes are a group of marine biomaterials that have recently drawn more attention because they are produced in harsh environmental conditions such as high salinity, extensive pH, a wide temperature range, and high pressure. Hence, marine-derived enzymes are capable of exhibiting remarkable properties due to their unique composition. In this review, we overviewed and discussed characteristics of marine enzymes as well as the sources of marine enzymes, ranging from primitive organisms to vertebrates, and presented the importance, advantages, and challenges of using marine enzymes with a summary of their applications in a variety of industries. Current biotechnological advancements need the study of novel marine enzymes that could be applied in a variety of ways. Resources of marine enzyme can benefit greatly for biotechnological applications duo to their biocompatible, ecofriendly and high effectiveness. It is beneficial to use the unique characteristics offered by marine enzymes to either develop new processes and products or improve existing ones. As a result, marine-derived enzymes have promising potential and are an excellent candidate for a variety of biotechnology applications and a future rise in the use of marine enzymes is to be anticipated.

Purification of Extracellular Protease from Staphylococcus simulans QB7and Its Ability in Generating Antioxidant and Anti-inflammatory Peptides from Meat Proteins

Proteases, especially microbial proteases, are widely used in food processing. The purpose of this study was aimed to purify an extracellular protease produced by the strain Staphylococcus simulans QB7 and to evaluate its ability in hydrolyzing meat proteins and generating antioxidant and anti-inflammatory peptides. The optimal conditions for producing the enzyme were as follows: inoculum ratio, 10%; initial pH, 6.5; temperature, 32 °C; incubation time, 36 h; and rotation speed, 160 rpm. The protease had a molecular weight of approximately 47 kDa, possessing the optimal activity at 50 °C, pH 7.0, The protease was stable at pH 4.0-8.0 and 30-60 °C, and the activity was improved by Na⁺, Mg²⁺, Ca²⁺, and Zn²⁺ ions, whereas it was inhibited by Cu²⁺, Co²⁺, Fe³⁺, Ba²⁺, Fe²⁺, β-M, and ethylene diamine tetraacetic acid disodium salt (EDTA). The protease could effectively hydrolyze meat proteins, and the generated hydrolysate could significantly inhibit tumor necrosis factor-alpha (TNFα)-induced oxidative stress, including superoxide and malondialdehyde levels and inflammation (vascular adhesion molecule-1 [VCAM-1] and cyclooxygenase 2 [COX2)) in human vascular EA.hy926 cells. The present findings support the ability of S. simulans QB7 protease in generating antioxidant and anti-inflammatory peptides during the fermentation of meat products.

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).

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.

Optimization of thermostable proteases production under agro-wastes solid-state fermentation by a new thermophilic Mycothermus thermophilus isolated from a hydrothermal spring Hammam Debagh, Algeria

The present work investigates for the first time the presence and isolation of the thermophilic fungi from hydrothermal spring situated at the locality of Guelma, in the Northeast of Algeria. The production of the thermostable proteases and the optimization of culture conditions under agro-wastes solid-state fermentation to achieve optimal production capacity were explored. A statistical experimental approach consisting of two designs was used to determine the optimum culture conditions and to attain the greatest enzyme production. Besides, different agricultural wastes were initially evaluated as a substrate, whereby wheat bran was selected for enzyme production by the isolate under solid-state conditions. The isolate thermophilic fungi were identified as Mycothermus thermophilus by sequencing the ITS region of the rDNA (NCBI Accession No: MK770356.1). Among the various screened variables: the temperature, the inoculum size, and the moisture were proved to have the most significant effects on protease activity. Employing two-level fractional Plackett-Burman and a Box-Behnken designs statistical approach helped in identifying optimum values of screened factors and their interactions. The analysis showed up 6.17-fold improvement in the production of proteases (~1187.03 U/mL) was achieved under the optimal conditions of moisture content 47%, inoculum 5 × 10⁵ spores/g, and temperature at 42 °C. These significant findings highlight the importance of the statistical design in isolation of Mycothermus thermophilus species from a specific location as well as identifying the optimal culture conditions for maximum yield.

Biochemical Characterization and Functional Analysis of Heat Stable High Potential Protease of Bacillus amyloliquefaciens Strain HM48 from Soils of Dachigam National Park in Kashmir Himalaya

A novel temperature stable alkaline protease yielding bacteria was isolated from the soils of Dachigam National Park, which is known to be inhabited by a wide variety of endemic plant and animal species of Western Himalaya. This high-potential protease producing isolate was characterized and identified as Bacillus amyloliquefaciens strain HM48 by morphological, Gram’s staining and biochemical techniques followed by molecular characterization using 16S rRNA approach. The extracellular protease of B. amyloliquefaciens HM48 was purified by precipitating with ammonium sulfate (80%), followed by dialysis and Gel filtration chromatography increasing its purity by 5.8-fold. The SDS–PAGE analysis of the purified enzyme confirmed a molecular weight of about ≈25 kDa. The enzyme displayed exceptional activity in a broad temperature range (10–90 °C) at pH 8.0, retaining its maximum at 70 °C, being the highest reported for this proteolytic Bacillus sp., with K_M and V_max of 11.71 mg/mL and 357.14 µmol/mL/min, respectively. The enzyme exhibited remarkable activity and stability against various metal ions, surfactants, oxidizing agent (H₂O₂), organic solvents and displayed outstanding compatibility with widely used detergents. This protease showed effective wash performance by exemplifying complete blood and egg-yolk stains removal at 70 °C and efficiently disintegrated chicken feathers making it of vital importance for laundry purpose and waste management. For functional analysis, protease gene amplification of strain HM48 yielded a nucleotide sequence of about 700 bp, which, when checked against the available sequences in NCBI, displayed similarity with subtilisin-like serine protease of B. amyloliquefaciens. The structure of this protease and its highest-priority substrate β-casein was generated through protein modeling. These protein models were validated through futuristic algorithms following which protein–protein (protease from HM48 and β-casein) docking was performed. The interaction profile of these proteins in the docked state with each other was also generated, shedding light on their finer details. Such attributes make this thermally stable protease novel and suitable for high-temperature industrial and environmental applications.

Identification of a Novel Thermostable Alkaline Protease from Bacillus megaterium-TK1 for the Detergent and Leather Industry

Simple Summary

In the current investigation, we describe the characteristic features of a novel Bacillus megaterium bacterium-derived protease with excellent thermostable enzyme activity under stringent alkaline conditions. The protease is highly compatible with various detergents and thus appears to be an eco-friendly additive for a variety of industrial applications.

Abstract

An increased need by the green industry for enzymes that can be exploited for eco-friendly industrial applications led us to isolate and identify a unique protease obtained from a proteolytic Bacillus megaterium-TK1 strain from a seawater source. The extracellular thermostable serine protease was processed by multiple chromatography steps. The isolated protease displayed a relative molecular weight (MW) of 33 kDa (confirmed by zymography), optimal enzyme performance at pH 8.0, and maximum enzyme performance at 70 °C with 100% substrate specificity towards casein. The proteolytic action was blocked by phenylmethylsulfonyl fluoride (PMSF), a serine hydrolase inactivator. Protease performance was augmented by several bivalent metal cations. The protease tolerance was studied under stringent conditions with different industrial dispersants and found to be stable with Surf Excel, Tide, or Rin detergents. Moreover, this protease could clean blood-stained fabrics and showed dehairing activity for cow skin with significantly reduced pollution loads. Our results suggest that this serine protease is a promising additive for various eco-friendly usages in both the detergent and leather industries.

A dual-functional aminopeptidase from Streptomyces canus T20 and its application in the preparation of small rice peptides

An aminopeptidase that derived from Streptomyces canus T20 (ScAP) was successfully expressed and characterized in Escherichia coli BL21 (DE3) for first time. The specific activity was 6000 U/mg, which is highest in Streptomyces aminopeptidases. Its optimal conditions were 60 °C and pH 8.0, respectively. ScAP exhibited excellent thermal and alkaline pH stability, retained 80.0% maximal activity at 50 °C for 200 h or at pH 9.0 for 24 h. Its activity observed to be complete inhibited by 0.1 mM EDTA and enhanced by Ca²⁺ and Co²⁺ to 115.4% and 104.0% respectively. ScAP also has exhibited high specificity towards rice protein on preparation of small peptides. The yield of small rice peptides achieved 66.5%, which is highest by far. Besides, ScAP have significant debittering effect on rice peptides. Results showed that bitter intensity score decreased by 49.0% with optimum condition (0.048% ScAP at 50 °C for 6 h). Therefore, ScAP as dual functional aminopeptidase of hydrolytic and debittering might have a potential application in the production of high yield and low bitterness of small rice peptides.

Biochemical and thermodynamic characteristics of a new serine protease from Mucor subtilissimus URM 4133

A protease from the fungus Mucor subtilissimus URM 4133, capable of producing bioactive peptides from goat casein, was purified. SDS-PAGE and zymography showed a molecular mass of 30 kDa. The enzyme was active and stable in a wide pH range (6.0–10.5) and (5.0–10.5), respectively. Optimum temperature was at 45–50 °C and stability was above 80 % (40 °C/2 h). Activity was not influenced by ions or organic substances (Triton, Tween, SDS and DMSO), but was completely inhibited by PMSF, suggesting that it belongs to the serine protease family. The Km and Vmax were 2.35 mg azocasein.mL-1 and 333.33 U.mg protein-1, respectively. Thermodynamic parameters of irreversible denaturation (40–60 °C) were enthalpy 123.63 – 123.46 kJ.mol-1, entropy 120.24–122.28 kJ.mol-1 and Gibbs free energy 85.97 – 82.45 kJ.mol-1. Any peptide sequences compatible with this protease were found after analysis by MALDI-TOF, which suggests that it is a new serine protease.

Homology modeling and heterologous expression of highly alkaline subtilisin-like serine protease from Bacillus halodurans C-125

Here we report heterologous expression, enzymatic characterization and structure homology modeling of a subtilisin-like alkaline serine protease (ASP) from Bacillus halodurans C-125. Encoding gene was successfully obtained by PCR and cloned into pMA0911 shuttle vector under the control of strong HpaII promoter and expressed extracellularly. ASP enzyme was successfully expressed in B. subtilis WB800 cell line lacking eight extracellular proteases and produced extracellularly in the culture medium. Km, Vmax and specific activity parameters of the recombinantly produced ASP were identified as 0.2899 mg/ml, 76.12 U/ml and 9500 U/mg, respectively. The purified enzyme revealed remarkable proteolytic activity at highly alkaline conditions with a pH optimum 12.0 and notable thermostability with temperature optimum at 60 °C. Furthermore, substrate-free enzyme revealed remarkable pH stability at pH 12.0 and maintained 93% of its initial activity when incubated at 37 °C for 24 h and 60% of its initial activity upon incubation at 60 °C for 1 h. Theoretically calculated molecular mass of ASP protein was confirmed through SDS-PAGE and western blot analysis (Mw: 28.3 kDa). The secondary and tertiary structures of ASP protein were also identified through homology modeling and further examined in detail. ASP harbors a typical S8/S53 peptidase domain comprising 17 β-sheets and 9 α-helixes within its secondary structure. The structure dynamics analysis of modeled 3D structure further revealed that transient inactivating propeptide chain is the most dynamic region of ASP enzyme with 8.52 Ų β-Factor value. Additional residue-dependent fluctuation plot analysis also confirmed the elevated structure dynamics patterning of ASP N-terminus which could be the potential prerequisite for the autonomous propeptide removal of alkaline serine peptidases. Yet the functional domain of ASP becomes quite stable after autonomous exclusion of its propeptide. Although the sequence homology between ASP and commercial detergent additive B. lentus protease (PDB ID:1GCI) was moderate (65.4% sequence similarity), their overlaid 3D structures revealed much higher similarity (98.14%) within 0.80 Å RMSD. In conclusions, with remarkable pH stability, notable thermostability and particularly high specific activity at extreme alkaline conditions, the unveiled ASP protein stands out as a novel protease candidate for various industrial sectors such as textile, detergent, leather, feed, waste, pharmaceutical and others.

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.

Alkaline serine protease from the new halotolerant alkaliphilic Salipaludibacillus agaradhaerens strain AK-R: purification and properties

Herein, we report the purification and characterization of an alkaline protease from the alkaliphilic Salipaludibacillus agaradhaerens (formerly Bacillus agaradhaerens) strain AK-R, which was previously isolated from Egyptian soda lakes. The purification procedures resulted in enzyme purification up to 13.3-fold, with a recovery yield of 16.3% and a specific activity of 3488 U/mg protein. AK-R protease was a monomeric protein with an estimated molecular weight of 33.0 kDa. The optimum pH and temperature for AK-R protease were pH 10 and 60 °C, respectively. The enzyme thermostability was significantly enhanced in the presence of CaCl₂ by approximately 1.3-fold. Moreover, under optimal conditions, the K _m and V _max values of the enzyme were 2.63 mg/ml and 4166.7 U/mg, respectively. PMSF caused complete inhibition of the enzyme activity, suggesting that AK-R belongs to the serine protease family. In addition, the enzyme was completely inhibited by EDTA, revealing the requirement of metal ions for AK-R protease activity; hence, it can be classified as a metalloprotease. AK-R protease is a mostly thiol-independent enzyme, since thiol reductants such as β-mercaptoethanol and dithiothreitol had no effect on the enzyme activity. AK-R protease exhibited high stability in several organic solvents, including butanol, amyl alcohol, dimethyl ether, toluene, diethyl ether and methanol. Moreover, AK-R protease showed significant stability to a variety of surfactants and commercial detergents. The features and properties of AK-R alkaline protease are favourable and suggest its potential applications in various industries, particularly in the laundry detergent industry.

Purification and biochemical characteristics of the extracellular protease from Pediococcus pentosaceus isolated from Harbin dry sausages

This study investigated the purification and biochemical characteristics of the protease produced by Pediococcus pentosaceus isolated from Harbin dry sausages. The optimized fermented conditions were as follows: fermentation time 36 h, initial pH 5 and fermentation temperature 30 °C. A 29.6 kDa extracellular protease was purified using ammonium sulphate deposition, ion exchange layer system and gel filtration. The protease produced by P. pentosaceus had a certain pH and thermal stability at pH 6 and 30 °C. The microbial protease activity could be inhibited by ethylene diamine tetraacetic acid disodium salt (EDTA). V_max and K_m of the protease were 43.9 mg/min and 8.3 mg/mL, respectively. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) reflected the ability of the protease to hydrolyse sarcoplasmic and myofibrillar proteins, particularly those of myosin heavy chain, paramyosin, actin, phosphorylase and creatine kinase-M types. 3D structure modelling of the P. pentosaceus protease found two domains in the protease protein and the correlation of the active sites with protease properties and substrate specificity. In conclusion, P. pentosaceus can be used as a starter culture or enzyme producing strain for inoculation in Harbin dry sausages.

Purification and biochemical characteristics of the microbial extracellular protease from Lactobacillus curvatus isolated from Harbin dry sausages

This study investigates the purification and biochemical characteristics of the protease secreted by Lactobacillus curvatus R5, which was isolated from Harbin dry sausages. The optimized fermentation conditions were fermentation time 36 h, initial pH 6 and fermentation temperature 37 °C. An extracellular protease was purified using ammonium sulfate precipitation, ion-exchange layer and gel filtration. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that molecular weight of the purified protease was 45.3 kDa. Protease produced by L. curvatus R5 reached a higher relative protease activity at pH 6, 40 °C, and the purified protease exhibited pH and thermal stability at pH 6 and 40 °C. The microbial protease activity can be inhibited by ethylene diamine tetraacetic acid disodium salt (EDTA). The V_max and K_m of the protease were 53 mg/min and 15.9 mg/mL, respectively. SDS-PAGE reflects the ability of the protease to hydrolyse myofibrillar protein and sarcoplasmic protein, especially on myosin heavy chain, actin, myosin light chain and phosphorylase. The 3D structure and the Ramachandran plot of L. curvatus R5 protease was obtained by homology modelling. The Ramachandran plot analysis revealed that the purified protease was composed of 366 amino acids, and its residues in favoured, allowed, generously allowed and disallowed regions were 84.6%, 11.3%, 3.2% and 0.9% residues, respectively. Molecular docking showed that the substrate actin bound to the protease active site by hydrogen bonding and hydrophobic interaction. This research provides a basis for understanding the enzymatic properties of L. curvatus R5 protease. In conclusion, L. curvatus R5 can be used as a starter culture or protease-producing strain to inoculate Harbin dry sausages.

Purification and characterization of alkaline protease with novel properties from Bacillus cereus strain S8

Proteases are the hydrolytic enzymes which hydrolyzes peptide bond between proteins with paramount applications in pharmaceutical and industrial sector. Therefore production of proteases with efficient characteristics of biotechnological interest from novel strain is significant. Hence, in this study, an alkaline serine protease produced by Bacillus cereus strain S8 (MTCC NO 11901) was purified and characterized. The alkaline protease was purified by ammonium sulfate precipitation (50%), ion exchange (DEAE-Cellulose) and gel filtration (Sephadex G-100) chromatographic techniques. As a result of this purification, a protein with specific activity of 300U/mg protein was obtained with purification fold 17.04 and recovery percentage of 34.6%. The molecular weight of the purified protease was determined using SDS-PAGE under non-reducing (71 kDa) and reducing conditions (35 kDa and 22 kDa). Zymogram analysis revealed that proteolytic activity was only associated with 22 kDa. These results indicate that existence of the enzyme as dimer in its native state. The molecular weight of the protease (22 kDa) was also determined by gel filtration (Sephadex G-200) chromatography and it was calculated as 21.8 kDa. The optimum activity of the protease was observed at pH 10.0 and temperature 70 °C with great stability towards pH and temperature with casein as a specific substrate. The enzyme was completely inhibited by PMSF and TLCK indicating that it is a serine protease of trypsin type. The enzyme exhibits a great stability towards organic solvents, oxidizing and bleaching agents and it is negatively influenced by Li²⁺ and Co²⁺ metal ions. The purified protein was further characterized by Matrix Assisted Laser Desorption Ionization/Mass Spectroscopy (MALDI/MS) analysis which reveals that total number of amino acids is 208 with isoelectric point 9.52.

A thermostable alkaliphilic protein-disulfide isomerase from Bacillus subtilis DR8806: cloning, expression, biochemical characterization and molecular dynamics simulation

Disulfide bonds are among the most important factors related to correct folding of the proteins. Protein disulfide isomerase (PDI) is the enzyme responsible for the correct formation and isomerization of these bonds. It is rarely studied so far and none of them showed industrial properties. In this study, the gene encoding for a putative PDI from Bacillus subtilis DR8806 was identified, cloned and expressed in Escherichia coli. It was encoded a 23.26kDa protein. The enzyme was purified by GST affinity chromatography with a specific activity of 1227u/mg. It was active and stable over a wide range of temperature (20-85°C) and pH (4.5-10) with an optimum at 65°C and pH 5.5. Its activity was enhanced by Mn²⁺ and Co²⁺ while Ag⁺ and Zn²⁺ decreased it. Some of the known PDI inhibitors such as Tocinoic acid and Bactiracin did not affect its activity. In-silico analysis shows the five amino acids changes in the protein sequence regarding to the consensus sequence of PDIs, have a positive impact toward the protein thermal stability. This was further confirmed by molecular dynamics simulations. By considering the overall results, the enzyme might be a potential candidate for applications in the respective industries.

Production, purification and characterization of a thermotolerant alkaline serine protease from a novel species Bacillus caseinilyticus

Alkaline proteases are important enzymes in many industrial applications, especially as additives in laundry detergent industry. Though there are a number of Bacillus species which are reported to be producing proteases, the efficiency of a protease produced by a novel strain has to be studied in comparison to the others. Hence, in this study, an alkaline serine protease produced by a novel species Bacilluscaseinilyticus was purified and characterized for its possible usage in detergent industry. Ammonium sulphate, dialysis and DEAE column chromatographic methods were used for purification of the isolated alkaline protease. The molecular weight of the protease was determined by SDS-PAGE and it was found to be 66 kDa. Peptide mass fingerprinting (PMF) was carried out using MALDI-TOF-TOF mass spectrometry and the peptides were found to be similar to that of subtilisin protease. Specific activity of purified protein was found to be 89.2 U/mg. Optimum pH and temperature for enzyme activity were at pH 8 and 60 °C, respectively, showing stability with 10 mM CaCl₂. Phenyl methyl sulphonyl fluoride (PMSF) at both 5 and 10 mM concentrations completely inhibited the enzyme activity suggesting its serine nature. EDTA, metal ions Mg²⁺ and Ca²⁺ increased the enzyme activity. The one factor at a time optimisation of the protease production was carried to identify the important factors that affect its production. After optimisation, the protease was produced at lab scale, purified and characterised. This alkali, thermotolerant serine protease was found to be significantly stable in the presence of various surfactants and H₂O_2. Also, it was successfully able to remove blood stain when used as an additive along with commercial detergent suggesting its potential application in the laundry detergent industry.