Molecular cloning and expression in yeast of caprine prochymosin

Biochemical Properties of a Promising Milk-Clotting Enzyme, Moose (Alces alces) Recombinant Chymosin

Moose (Alces alces) recombinant chymosin with a milk-clotting activity of 86 AU/mL was synthesized in the Kluyveromyces lactis expression system. After precipitation with ammonium sulfate and chromatographic purification, a sample of genetically engineered moose chymosin with a specific milk-clotting activity of 15,768 AU/mg was obtained, which was used for extensive biochemical characterization of the enzyme. The threshold of the thermal stability of moose chymosin was 55 °C; its complete inactivation occurred after heating at 60 °C. The total proteolytic activity of moose chymosin was 0.332 A280 units. The ratio of milk-clotting and total proteolytic activities of the enzyme was 0.8. The Km, kcat and kcat/Km values of moose chymosin were 4.7 μM, 98.7 s-1, and 21.1 μM-1 s-1, respectively. The pattern of change in the coagulation activity as a function of pH and Ca2+ concentration was consistent with the requirements for milk coagulants for cheese making. The optimum temperature of the enzyme was 50-55 °C. The introduction of Mg2+, Zn2+, Co2+, Ba2+, Fe2+, Mn2+, Ca2+, and Cu2+ into milk activated the coagulation ability of moose chymosin, while Ni ions on the contrary inhibited its activity. Using previously published data, we compared the biochemical properties of recombinant moose chymosin produced in bacterial (Escherichia coli) and yeast (K. lactis) producers.

Biochemical and technological properties of moose (<i>Alces alces</i>) recombinant chymosin

Recombinant chymosins (rСhns) of the cow and the camel are currently considered as standard milk coagulants for cheese-making. The search for a new type of milk-clotting enzymes that may exist in nature and can surpass the existing “cheese-making” standards is an urgent biotechnological task. Within this study, we for the first time constructed an expression vector allowing production of a recombinant analog of moose chymosin in the expression system of Escherichia coli (strain SHuffle express). We built a model of the spatial structure of moose chymosin and compared the topography of positive and negative surface charges with the correspondent structures of cow and camel chymosins. We found that the distribution of charges on the surface of moose chymosin has common features with that of cow and camel chymosins. However, the moose enzyme carries a unique positively charged patch, which is likely to affect its interaction with the substrate. Biochemical and technological properties of the moose rChn were studied. Commercial rСhns of cow and camel were used as comparison enzymes. In some technological parameters, the moose rChn proved to be superior to the reference enzymes. Сompared with the cow and camel rСhns, the moose chymosin specific activity is less dependent on the changes in CaCl2 concentration in the range of 1–5 mM and pH in the range of 6–7, which is an attractive technological property. The total proteolytic activity of the moose rСhn occupies an intermediate position between the rСhns of cow and camel. The combination of biochemical and technological properties of the moose rСhn argues for further study of this enzyme.

Challenging Sustainable and Innovative Technologies in Cheese Production: A Review

It is well known that cheese yield and quality are affected by animal genetics, milk quality (chemical, physical, and microbiological), production technology, and the type of rennet and dairy cultures used in production. Major differences in the same type of cheese (i.e., hard cheese) are caused by the rennet and dairy cultures, which affect the ripening process. This review aims to explore current technological advancements in animal genetics, methods for the isolation and production of rennet and dairy cultures, along with possible applications of microencapsulation in rennet and dairy culture production, as well as the challenge posed to current dairy technologies by the preservation of biodiversity. Based on the reviewed scientific literature, it can be concluded that innovative approaches and the described techniques can significantly improve cheese production.

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.

Characterization of the Altai Maral Chymosin Gene, Production of a Chymosin Recombinant Analog in the Prokaryotic Expression System, and Analysis of Its Several Biochemical Properties

For the first time, the chymosin gene (CYM) of a maral was characterized. Its exon/intron organization was established using comparative analysis of the nucleotide sequence. The CYM mRNA sequence encoding a maral preprochymosin was reconstructed. Nucleotide sequence of the CYM maral mRNA allowed developing an expression vector to ensure production of a recombinant enzyme. Recombinant maral prochymosin was obtained in the expression system of Escherichia coli [strain BL21 (DE3)]. Total milk-coagulation activity (MCA) of the recombinant maral chymosin was 2330 AU/ml. The recombinant maral prochymosin relative activity was 52955 AU/mg. The recombinant maral chymosin showed 100-81% MCA in the temperature range 30-50°C, thermal stability (TS) threshold was 50°C, and the enzyme was completely inactivated at 70°C. Preparations of the recombinant chymosin of a single-humped camel and recombinant bovine chymosin were used as reference samples. Michaelis-Menten constant (K_m), turnover number (k_cat), and catalytic efficiency (k_cat/K_m) of the recombinant maral chymosin, were 1.18 ± 0.1 µM, 2.68 ± 0.08 s^-1 and 2.27± 0.10 µm M^-1·s^-1, respectively.

Effect of Oryctolagus cuniculus (rabbit) rennet on the texture, rheology, and sensory properties of white cheese

Calf rennet has long been used in cheese-making. Because of calf rennet shortage and high cost, novel proteases were needed to meet industry's increasing enzyme demand. Recombinant chymosins and camel chymosin were started to be used in the industry. There is no study in the literature subjecting use of rabbit rennet in cheese production. Chemical, rheological, and sensorial characteristics of white cheese made with rabbit rennet were investigated in this study. Quality characteristics of rabbit rennet cheese (RC) were compared to cheeses produced with commercial calf (CC) and camel chymosins (CLC). RC and CLC exhibited higher hardness and dynamic moduli values throughout the storage as compared to CC. Although moisture levels of cheese samples were similar at day 60, CC had much lower hardness and dynamic moduli values than CLC and RC. While the appearance and structure were better for CLC, the highest odor and taste scores were obtained by RC during 60 days of storage. The results of this investigation proposed that rabbit rennet could be a suitable milk coagulant for white cheese production. Our results showed that rabbit rennet has comparable cheese-making performance with camel chymosin and could be a good alternative for calf chymosin.

Cloning and Expression of Yak Active Chymosin in Pichia pastoris

Rennet, a complex of enzymes found in the stomachs of ruminants, is an important component for cheese production. In our study, we described that yak chymosin gene recombinant Pichia pastoris strain could serve as a novel source for rennet production. Yaks total RNA was extracted from the abomasum of an unweaned yak. The yak preprochymosin, prochymosin, and chymosin genes from total RNA were isolated using gene specific primers based on cattle chymosin gene sequence respectively and analyzed their expression pattern byreal time-polymerase chain reaction. The result showed that the chymosin gene expression level of the sucking yaks was 11.45 times higher than one of adult yaks and yak chymosin belongs to Bovidae family in phylogenetic analysis. To express each, the preprochymosin, prochymosin, and chymosin genes were ligated into the expression vector pPICZαA, respectively, and were expressed in Pichia pastoris X33. The results showed that all the recombinant clones of P. pastoris containing the preprochymosin, prochymosin or chymosin genes could produce the active form of recombinant chymosin into the culture supernatant. Heterologous expressed prochymosin (14.55 Soxhlet unit/mL) had the highest enzyme activity of the three expressed chymosin enzymes. Therefore, we suggest that the yak chymosin gene recombinant Pichia pastoris strain could provide an alternative source of rennet production.

Cloning and expression of buffalo active chymosin in Pichia pastoris

To date, only recombinant chymosin has been obtained in its active form from supernatants of filamentous fungi, which are not as good candidates as yeasts for large-scale fermentations. Since Bos taurus chymosin was cloned and expressed, the world demand for this protease has increased to such an extent that the cheesemaking industry has been looking for novel sources of chymosin. In this sense because buffalo chymosin has properties that are more stable than those of B. taurus chymosin, it may occupy a space of its own in the chymosin market. The main objective of the present work was the production of active recombinant buffalo chymosin in the culture supernatant of Pichia pastoris . This yeast has demonstrated its usefulness as an excellent large-scale fermentation tool for the secretion of recombinant foreign proteins. RNA was extracted from the abomasum of a suckling calf water buffalo ( Bubalus arnee bubalis ). Preprochymosin, prochymosin, and chymosin DNA sequences were isolated and expressed into P. pastoris. Only the recombinant clones of P. pastoris containing the prochymosin sequence gene were able to secrete the active form of the chymosin to the culture supernatant. This paper describes for the first time the production of active recombinant chymosin in P. pastoris without the need of a previous in vitro activation. The new recombinant yeast strain could represent a novel and excellent source of rennet for the cheesemaking industry.

Purification and characterization of milk clotting enzyme from goat (Capra hircus)

Chymosin, the major component of rennet (milk clotting enzyme), is an acid protease produced in the fourth stomach of milk-fed ruminants including goat and sheep in the form of an inactive precursor prochymosin. It is responsible for hydrolysis of kappa-casein chain in casein micelles of milk and therefore, used as milk coagulant in cheese preparation. The present investigation was undertaken to purify and characterize goat (Capra hircus) chymosin for its suitability as milk coagulant. The enzyme was extracted from abomasal tissue of kid and purified nearly 30-fold using anion exchanger and gel filtration chromatography. Goat chymosin resolved into three major active peaks, indicating possible heterogeneity when passed through DEAE-cellulose ion exchange column. The purified enzyme had a molecular mass of 36 kDa on SDS-PAGE, which was further confirmed by Western blot analysis. The purified enzyme preparation was stable up to 55 degrees C with maximum activity at 30 degrees C. The milk clotting activity was decreased steadily as pH is increased and indicated maximum activity at pH 5.5. Proteolytic activity of goat chymosin increased with incubation time at 37 degrees C. Goat chymosin was found to be more thermostable than cattle chymosin and equally stable to buffalo chymosin.

Heterologous protein production in the yeastKluyveromyces lactis

Kluyveromyces lactis is both scientifically and biotechnologically one of the most important non-Saccharomyces yeasts. Its biotechnological significance builds on its history of safe use in the food industry and its well-known ability to produce enzymes like lactase and bovine chymosin on an industrial scale. In this article, we review the various strains, genetic techniques and molecular tools currently available for the use of K. lactis as a host for protein expression. Additionally, we present data illustrating the recent use of proteomics studies to identify cellular bottlenecks that impede heterologous protein expression.