Novel milk-clotting enzyme from Bacillus stearothermophilus as a coagulant in UF-white soft cheese

Milk clotting enzymes from marine resources and their role in cheese-making: A mini review

With the continual increase in global cheese consumption, rennet, the traditional milk coagulant, is unable to meet the growing demand in cheese production. Although several proteases from other sources have been used for cheese-making, they suffer various shortcomings. The ocean is home to a huge and diverse range of life forms, which represent a vast potential source of proteases. Marine proteases have been isolated from a number of marine species, including sponge, jellyfish, seaweed and marine animals, and some have been shown to be suitable as milk-clotting enzymes for cheese making. This review summarizes the latest studies on rennet substitutes from marine resources and their role in cheese-making. The emphasis of the review is on the isolation and purification of the marine proteases, the biochemical characteristics of these enzymes, especially their caseinolytic and milk-clotting properties, as well as their cleavage sites on casein. Some of the marine proteases have been applied as milk-clotting agent in cheese-making, with the resultant production of cheese with comparable characteristics, including sensory characteristics, to calf rennet cheese. The review concludes by highlighting the challenges and opportunities for future research in the field.

The catalytic and kinetic characterization of Bacillus subtilis MK775302 milk clotting enzyme: comparison with calf rennet as a coagulant in white soft cheese manufacture

BACKGROUND

Calf rennet is considered the traditional source of milk clotting enzyme (MCE). However, increasing cheese consumption with decreasing the calf rennet supply had encouraged the quest for new rennet alternatives. The purpose of this study is to acquire more information about the catalytic and kinetic properties of partially purified Bacillus subtilis MK775302 MCE and to assess the role of enzyme in cheese manufacture.

RESULTS

B. subtilis MK775302 MCE was partially purified by 50% acetone precipitation with 5.6-fold purification. The optimum temperature and pH of the partially purified MCE were 70 °C and 5.0, respectively. The activation energy was calculated as 47.7 kJ/mol. The calculated Km and Vmax values were 36 mg/ml and 833 U/ml, respectively. The enzyme retained full activity at NaCl concentration of 2%. Compared to the commercial calf rennet, the ultra-filtrated white soft cheese produced from the partially purified B. subtilis MK775302 MCE exhibited higher total acidity, higher volatile fatty acids, and improved sensorial properties.

CONCLUSIONS

The partially purified MCE obtained in this study is a promising milk coagulant that can replace calf rennet at a commercial scale to produce better-quality cheese with improved texture and flavor.

Thermostable trypsin-like protease by Penicillium roqueforti secreted in cocoa shell fermentation: Production optimization, characterization, and application in milk clotting

The increased demand for cheese and the limited availability of calf rennet justifies the search for milk-clotting enzymes from alternative sources. Trypsin-like protease by Penicillium roqueforti was produced by solid-state fermentation using cocoa shell waste as substrate. The production of a crude enzyme extract that is rich in this enzyme was optimized using a Doehlert-type multivariate experimental design. The biochemical characterization showed that the enzyme has excellent activity and stability at alkaline pH (10-12) and an optimum temperature of 80°C, being stable at temperatures above 60°C. Enzymatic activity was maximized in the presence of Na⁺ (192%), Co²⁺ (187%), methanol (153%), ethanol (141%), and hexane (128%). Considering the biochemical characteristics obtained and the milk coagulation activity, trypsin-like protease can be applied in the food industry, such as in milk clotting and in the fabrication of cheeses.

Utility of Moringa oleifera waste as a coagulant in goat soft cheese production

Milk clotting enzyme (MCE) of Moringa oleifera from prepared seed cake (PSC) dissolved in acetate buffer pH 5.0 recorded the highest activity compared to other samples, as well as 20–40% saturation of ammonium sulfate precipitated MCE with 28.20% yield and 1.01 purification fold. The proteolytic activity (PA) of crude MCE from Moringa oleifera PSC was higher than those of partial purified MCE with 180.81 and 155.47 as MCA/PA ratio, respectively. PSC moringa MCE exhibited their optimal activity at pH 5.0 and 60 °C; it could be capable to coagulate different milk types. Also, goat soft cheeses coagulated with moringa MCE exhibited significantly (p ≤ 0.05) higher levels of water soluble nitrogen content and total sensorial scores than control cheese. It could be concluded that partial purified MCE from Moringa oleifera PSC may prove to be a good candidate in goat cheese production without any appeared defects during their storage period.

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Milk clotting enzyme was purified from moringa waste resulted during oil extraction.

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Purified milk clotting enzyme from moringa waste could be used as calf substitute.

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Moringa milk clotting enzyme could be used as a coagulant for different milk types.

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No bitterness appeared in goat cheese coagulated with moringa milk clotting enzyme.

Structural Analysis of a Novel Aspartic-Type Endopeptidase from Moringa oleifera Seeds and Its Milk-Clotting Properties

A novel aspartic-type endopeptidase was previously obtained from Moringa oleifera seeds; however, its specific milk-clotting properties have remained unclear. Here, we used various biophysical and molecular simulation approaches for characterizing the structure and function of the aspartic-type endopeptidase. The endopeptidase was preferentially active toward κ-casein (CN) and hydrolyzed it more than calf rennet; however, its ability to hydrolyze α-CN and β-CN was weaker than that of calf rennet. The endopeptidase cleaved κ-CN at Gln135-Asp136 and generated a 15 588.18 Da peptide with 135 amino acids. We further simulated the docking complex of the endopeptidase and κ-CN and found out that they possibly combined with each other via hydrogen bonds. The flocculation reaction between the endopeptidase and κ-CN indicated that milk coagulation occurred within 60 min. Overall, our observations suggest that the aspartic-type endopeptidase can be a potential rennet alternative for cheese making.

Constitutive expression of Camelus bactrianus prochymosin B in Pichia pastoris

Camel chymosin can be efficiently employed to produce cheese. Traditionally the rennet enzyme produced by the glands of the fourth stomach of ruminant animals (abomassum) is used in cheese making. Full-length Camelus bactrianus (Bactrian camel) prochymosin gene was synthesized and constitutively expressed in Pichia pastoris cells under glyceraldehydes-3-phosphate dehydrogenase (GAP) promoter. It was purified by sequential anion and cation exchange chromatography. SDS-PAGE analysis resulted in two bands, approximately 42 and 35 kDa. The 42 kDa band vanished when the sample was treated with endoglycosidase H, indicating that the recombinant protein is partially glycosylated. Optimal pH for the activity of the highest-purity recombinant chymosin was pH 4.5 for cow's milk and pH 4.0 for mare's milk. The range 45-50 °C and 70 °C for cow's and mare's milk types, respectively, was found to be the most appropriate for maximal relative milk-clotting activity. Concentration of CaCl2 that ensured the stability of the chymosin milk-clotting activity was between 20 and 50 mM with an optimum at 30 mM. Milk-clotting activity of camel recombinant chymosin and ability to make curd was successfully tested on fresh mare's milk. Pichia pastoris strain with integrated camel chymosin gene showed high productivity of submerged fermentation in bioreactor with milk-clotting activity 1412 U/mL and 80 mg/L enzyme yield. These results suggest that the constitutive expression of the camel chymosin Camelus bactrianus in the yeast Pichia pastoris has good prospects for practical applications.

Application of artificial neural networks to predict multiple quality of dry-cured ham based on protein degradation

This study investigated protein degradation and quality changes during the processing of dry-cured ham, and then established the multiple quality prediction model based on protein degradation. From the raw material to the curing period, proteolysis index of external samples were higher than that of internal samples, however, the difference gradually decreased from the drying period to the maturing period. Protein degradation can be used as indicators for controlling quality of the hams. With protein degradation index as input variables, the back propagation-artificial neural networks (BP-ANN) models were optimized, with training function of trainlm, transfer function of logsig in input-hidden layer and tansig in hidden-output layer, and 20 hidden layer neurons. Furthermore, the relative errors of predictive data and experimental data of 12 samples were approximately 0 with the BP-ANN model. Results indicated that the BP-ANN has great potential in predicting multiple quality of dry-cured ham based on protein degradation.

Application of Milk-Clotting Protease from Aspergillus oryzae DRDFS13 MN726447 and Bacillus subtilis SMDFS 2B MN715837 for Danbo Cheese Production

This study aimed to investigate the efficiency, biochemical composition, and sensory quality of Danbo cheese produced using proteases derived from the fungus and bacterium compared to the commercial product. A fungal enzyme from Aspergillus oryzae DRDFS13MN726447 and a bacterial enzyme from Bacillus subtilis SMDFS 2B MN715837 were produced by solid-state and submerged fermentation, respectively. The crude enzyme from A. oryzae DRDFS13 and B. subtilis SMDFS 2B was partially purified by dialysis and used for Danbo cheese production using commercial rennet (CHY-MAX® Powder Extract NB, Christian Hansen, 2235 IMCU/g) as a control. The Danbo cheese produced using dialyzed fungal enzyme (E1) (267 U/mL), dialyzed bacterial enzyme (E2) (522 U/mL), and commercial rennet (C) were analyzed for body property, organoleptic characteristics, and proximate and mineral composition when fresh and after 2 months of ripening. There was no significant difference in the cheese yield (C = 9 kg, E1 = 8.6 kg, and E2 = 8.9 kg) among the three treatments. The body properties of Danbo cheese produced with the fungal enzyme (E1) were firm and acceptable as the control (C), whereas the Danbo cheese produced by bacterial enzymes has shown a watery body. The overall organoleptic characteristics of Danbo cheese produced by the fungal enzyme (5.3) were similar to control cheese produced by commercial rennet (5.5). Both cheese types were significantly different in organoleptic properties from Danbo cheese produced by the bacterial enzyme (4.9). There was no significant difference (p>0.05) in the proximate composition between the ripened Danbo cheese produced by fungal enzyme and the control cheese except for crude protein content. However, the ripened cheese products showed a significant difference in their mineral composition except for sodium. In conclusion, this study demonstrated that the fungal enzyme from Aspergillus oryzae DRDFS 13 is more appropriate for Danbo cheese production than the bacterial enzyme from Bacillus subtilis SMDFS 2B. However, it requires further application of the enzymes for the production of other cheese varieties.

Effects of blends of camel and calf chymosin on proteolysis, residual coagulant activity, microstructure, and sensory characteristics of Beyaz peynir

Beyaz peynir, a white brined cheese, was manufactured using different blends of camel chymosin (100, 75, 50, 25, and 0%) with calf chymosin and ripened for 90 d. The purpose of this study was to determine the best mixture of coagulant for Beyaz peynir, in terms of proteolysis, texture, and melting characteristics. The cheeses were evaluated in terms of chemical composition, levels of proteolysis, total free amino acids, texture, meltability, residual coagulant activity, microstructure, and sensory properties during 90 d of ripening. Differences in the gross chemical composition were statistically significant for all types of cheeses. Levels of proteolysis were highly dependent on the blends of the coagulants. Higher proteolysis was observed in cheeses that used a higher ratio of calf chymosin. Differences in urea-PAGE and peptide profiles of each cheese were observed as well. Meltability values proportionally increased with the higher increasing levels of calf chymosin in the blend formula. These coagulants had a slight effect on the microstructure of cheeses. The cheese made with camel chymosin had a harder texture than calf chymosin cheese, and hardness values of all cheese samples decreased during ripening. The cheeses with a high ratio of calf chymosin had higher residual enzyme activity than those made with camel chymosin. No significant difference in sensory properties was observed among the cheeses. In conclusion, cheeses made with a high level of calf chymosin had a higher level of proteolysis, residual coagulant activity, and meltability. The cheeses also had a softer texture than cheeses made with a high content of camel chymosin. Camel chymosin may be used as a coagulant alone if low or limited levels of proteolysis are desired in cheese.

Catalytic, kinetic and thermodynamic properties of free and immobilized caseinase on mica glass-ceramics

Bacillus megaterium 314 strain was able to utilize agricultural and industrial wastes for metallo-protease production. Orange peel and wheat bran were found as the most suitable carbon and nitrogen sources, respectively. Optimized production process enhanced the enzyme production by 5.1-folds. Glass and glass-ceramic with different particle sizes based on mica were used as inorganic carrier. Protease enzyme was immobilized by covalent bonding and physical adsorption methods on nanoparticle supports. Enzyme physically adsorbed on glass ceramic (particle size 0.71-1.0 mm) had the highest residual activity and the highest immobilization yield. Glass-ceramic was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Immobilized enzyme exhibited activation energy (E a ) and deactivation rate constant at 60 °C (k d ) about 1.29 and 1.46-times, respectively lower than free enzyme. Moreover, adsorbed enzyme had higher energy for denaturation (E d ), half-life (t 1/2 ), and decimal reduction time (D). The thermodynamic parameters of irreversible thermal denaturation for the protease enzyme indicate that immobilized enzyme had higher enthalpy (ΔH°), free energy (ΔG°), and entropy (ΔS°) than free one. There was a significant improvement in the maximum reaction velocity Vmax (2.5-fold), Michaelis constant Km (1.9-fold), and catalytic efficiency Vmax/Km (4.7-fold) values after immobilization indicating the efficiency and effectiveness of immobilization approach.

A systematic reconsideration on proteases

Proteases are a group of large complex enzyme molecules that perform highly focused proteolysis functions. A vast quantity of the protease enzymes is predominantly sourced from microbial fermentation process, although proteases tend to natively present in plant, animals and humans. Proteases possess a pervasive importance in medical and pharmaceutical sector, because of its enriched specificity towards biomolecules. They are also actively encompassed in regulating certain physiological pathways. A distinct territory of human disorders is treated by substrate specific proteases. Enormous numbers of catalytic activities in habitual metabolism process of a living organism are protease dependent. Pilot scale researches and product development in industrial biotechnology sectors are wholly based on any one of the protease enzymes. The applications of the protease enzymes and its economic benefits of being an eco-friendly material are far-reaching. This review presents a brief overview on the classification and sources of various types of proteases. We describe the essential evidences of role of protease in different sectors. The proteases could be a potential relieves to harmful synthetic chemicals in distinctive industrial processes and thus gains global perception.

Newly Effective Milk-Clotting Enzyme from Bacillus subtilis and Its Application in Cheese Making

A new effective milk-clotting enzyme (BY-1) was produced from Bacillus subtilis PNG27. The analysis of MALDI-TOF-MS/MS showed that it belongs to the peptidase M4 family and had 521 amino acids. It had a higher proteolytic activity on α-casein, β-casein, κ-casein, and β-lactoglobulin than Rennet. Besides, BY-1 could decrease the curd time of poor-curd, UHT, refrigerated, and reconstituted milk. Moreover, two kinds of cheese were, respectively, made by BY-1 and Rennet. The results showed that the protein hydrolysates (WSN, CTA-N, and PTA-N) of cheese made by BY-1 were higher than that of Rennet. Flavor compounds (28) were detected from the cheese made by BY-1, whereas 15 compounds were detected from Rennet. The sensory evaluation indicated that the cheese produced by BY-1 exhibited better flavor and overall acceptability. Therefore, BY-1 could be widely used in cheese production.

The effect of ultrasound treatment on microbial and physicochemical properties of Iranian ultrafiltered feta-type cheese

Pasteurization failures in the dairy industry have been reported in many previous studies. Hence, ultrasound, as a nonthermal alternative to pasteurization, has been studied in recent years. In this research, retentate of ultrafiltered milk was pasteurized, inoculated with Escherichia coli O157:H7, Staphylococcus aureus, Penicillium chrysogenum, or Clostridium sporogenes, and then treated with ultrasound for 20 min at frequencies of 20, 40, and 60 kHz and intensity of 80%. Microbial and physicochemical properties of the subsequently produced ultrafiltered white cheeses were investigated throughout 60 d of ripening. Sonication at 20, 40, and 60 kHz reduced counts of E. coli O157:H7, S. aureus, P. chrysogenum, and Cl. sporogenes by 4.08, 4.17, and 4.28 log; 1.10, 1.03, and 1.95 log; 1.11, 1.07, and 1.11 log; and 2.11, 2.03, and 2.17 log, respectively. Sonication improved the acidity of ripened cheese, and sonicated samples had lower pH values than control samples at the end of storage. Sonication did not affect fat in dry matter or the protein content of cheese during ripening, but it did accelerate lipolysis and proteolysis; the highest rates of lipolysis index (free fatty acid content) and proteolysis index (water-soluble nitrogen) were observed on d 60 of ripening for samples sonicated at 60 kHz. Sonication did not affect cohesiveness or springiness of cheese samples, but hardness and gumminess increased in the first 30 d and then decreased until 60 d of storage. Furthermore, ultrasound treatment improved organoleptic properties of the cheese. In terms of overall acceptance, samples sonicated at 60 kHz received the highest sensorial scores. Results showed that sonication can improve microbial, physicochemical, and sensorial properties of ultrafiltered white cheese.

Improving the catalytic, kinetic and thermodynamic properties of Bacillus subtilis KU710517 milk clotting enzyme via conjugation with polyethylene glycol

Milk clotting enzyme (MCE) produced by Bacillus subtilis KU710517 was conjugated to several activated polysaccharides. Among all the conjugates, the enzyme conjugated with polyethylene glycol (PEG) exhibited the highest retained activity (551U/mg protein) with a recovered activity of 95.3%. The activation energy of PEG-conjugated enzyme was calculated as 24.56kJ·mol^-1which was lower than that of the native one (29.27kJ·mol^-1) however, the temperature quotient (Q₁₀) was about 1.08 for the two forms of the enzyme. The calculated half-life times of PEG-conjugated enzyme at 55 and 60°C were 317.78 and 128.6min respectively, whereas at the same temperatures the native enzyme had lower half-life times (53 and 19.6min respectively). The data of thermodynamic analysis for substrate catalysis including the specificity constant (V_max/K_m), turnover number (k_cat), catalytic efficiency (k_cat/K_m), enthalpy of activation (ΔH*), free energy of activation (ΔG*), free energy for transition state formation ΔG*_E-T and free energy of substrate binding ΔG*_E-S were determined for both native and PEG-conjugated enzyme. In addition, the thermodynamic parameters for irreversible inactivation (ΔH, ΔG, ΔS) were evaluated. The calculated results indicated that the catalytic properties after the PEG-conjugation were significantly improved.