Characterization of the purified actinidin as a plant coagulant of bovine milk

Efficient three phase partitioning of actinidin from kiwifruit (Actinidia deliciosa) and its characterization

Three phase partitioning (TPP) method was effectively utilized for the extraction and purification of milk clotting protease (actinidin) from the kiwifruit pulp. The different purification parameters of TPP such as ammonium sulfate saturation, ratio of the crude kiwifruit extract to tert-butanol, and the pH value of extract were optimized. The 40% (w/v) salt saturation having 1.0:0.75 (v/v) ratio of crude kiwifruit extract to tert-butanol at 6.0 pH value exhibited 3.14 purification fold along with 142.27% recovery, and the protease was concentrated exclusively at intermediate phase (IP). This fraction showed milk-clotting activity (MCA), but there was no such activity in lower aqueous phase (AP). The enzyme molecular weight was found to be 24 kDa from Tricine SDS-PAGE analysis. Recovered protease demonstrated greater stability at pH 7.0 and temperature 50 °C. The Vmax and Km values were 121.9 U/ml and 3.2 mg/ml respectively. Its cysteine nature was demonstrated by inhibition studies. This study highlighted that the TPP is an economic and effective method for extraction and purification of actinidin from kiwifruit, and it could be used as a vegetable coagulant for cheesemaking.

Plant-derived rennet: research progress, novel strategies for their isolation, identification, mechanism, bioactive peptide generation, and application in cheese manufacturing

Rennet, an aspartate protease found in the stomach of unweaned calves, effectively cuts the peptide bond between Phe105-Met106 in κ-casein, hydrolyzing the casein micelles to coagulate the milk and is a crucial additive in cheese production. Rennet is one of the most used enzymes of animal origin in cheese making. However, using rennet al.one is insufficient to meet the increasing demand for cheese production worldwide. Numerous studies have shown that plant rennet can be an alternative to bovine rennet and exhibit a good renneting effect. Therefore, it is crucial and urgent to find a reliable plant rennet. Based on our team's research on rennet enzymes of plant origin, such as from Dregea sinensis Hemsl. and Moringa oleifer Lam., for more than ten years, this paper reviews the relevant literature on rennet sources, isolation, identification, rennet mechanism, functional active peptide screening, and application in cheese production. In addition, it proposes the various techniques for targeted isolation and identification of rennet and efficient screening of functionally active peptides, which show excellent prospects for development.

Purification and characteristics of a novel milk-clotting metalloprotease from Bacillus velezensis DB219

Milk-clotting enzyme (MCE) is the essential active agents in dairy processing. The traditional MCE is mainly obtained from animal sources, in which calf rennet is the most widely used in cheese industry. Traditional MCE substitute is becoming necessary due to its limited production and increased cheese consumption. A novel traditional MCE substitute was produced from Bacillus velezensis DB219 in this study. The DB219 MCE exhibited a notable specific activity of 6,110 Soxhlet units/mg and 3.16-fold purification yield with 28.87% recovery through ammonium sulfate fractionation and DEAE-Sepharose Fast Flow. The purified DB219 MCE was a metalloprotease with a molecular weight of 36 kDa. The DB219 MCE was weak acid resistance and stable at pH 6.0 to 10.0 and temperature <45°C. The highest milk-clotting activity was observed in substrate at pH 5.5 added with 20 to 30 mM CaCl2. The Michaelis constant and maximal velocity for casein were 0.31 g/L and 14.22 μmol/min. The DB219 MCE preferred to hydrolyze β-casein instead of α-casein. The DB219 MCE hydrolyzed α-casein, β-casein, and κ-casein to generate significantly different peptides in comparison with calf rennet and ES6023 MCE (fungal MCE) through SDS-PAGE and reversed-phase HPLC analysis. The DB219 MCE mainly cleaved Thr124-Ile125 and Ser104-Phe105 bonds in κ-casein and had unique casein cleavage sites and peptide composition through LC-MS/MS analysis. The DB219 MCE was potential to be a new milk coagulant and enriched kinds of traditional MCE substitute.

An Easy and Cheap Kiwi-Based Preparation as Vegetable Milk Coagulant: Preliminary Study at the Laboratory Scale

In the present study, a kiwifruit aqueous extract was developed and used as a coagulant enzyme in cheesemaking. In detail, polyacrylamide gel electrophoresis (SDS-PAGE) was used to investigate the presence of actinidin, the kiwifruit enzyme involved in κ-casein hydrolysis, in different tissues (pulp, peel, and whole fruit) of ripe and unripe kiwifruits. Data revealed the presence of the enzyme both in the peel and in the pulp of the fruit. Although the aqueous extract obtained from the kiwifruit peel was able to hydrolyze semi-skimmed milk, it did not break down κ-casein. The aqueous extract obtained from the pulp showed a hydrolytic activity toward both κ-casein and semi-skimmed milk. The values for milk-clotting and proteolytic activity of the kiwifruit pulp extract were evaluated at different temperatures and pH parameters in order to obtain a high value of the MCA/PA ratio; we found that a temperature of 40 °C in combination with a pH value of 5.5 allowed us to obtain the best performance. In addition, the data revealed a higher hydrolytic activity of the enzymatic preparation from ripe kiwifruits than that from unripe ones, suggesting the use of the extract from pulp of ripe kiwifruits in the laboratory-scale cheesemaking. The data showed that 3% (v/v) of the ripe kiwifruit pulp extract determined a curd yield of 20.27%, comparable to chymosin yield. In conclusion, the extraction procedure for kiwifruit aqueous extract proposed in the present study was shown to be a fast, cheap, chemical-free, and ecofriendly technology as a plant coagulant for cheese manufacturing.

Plant Milk-Clotting Enzymes for Cheesemaking

The reduced availability and the increasing prices of calf rennet, coupled to the growing global demand of cheese has led, worldwide, to explore alternative clotting enzymes, capable to replace traditional rennet, during the cheesemaking. In addition, religious factors and others related to the vegetarianism of some consumers, have led to alternative rennet substitutes. Nowadays, several plant-derived milk-clotting enzymes are available for cheesemaking technology. Many efforts have also been made to compare their effects on rheological and sensory properties of cheese to those arising from animal rennet. However, vegetable clotting enzymes are still partially suitable for cheesemaking, due to excessive proteolytic activity, which contribute to bitter flavor development. This review provides a literature overview of the most used vegetable clotting enzymes in cheese technology, classified according to their protease class. Finally, clotting and proteolytic activities are discussed in relation to their application on the different cheesemaking products.

The in-vitro digestion behaviors of micellar casein acting as wall materials in spray-dried microparticles: The relationships between colloidal calcium phosphate and the release of loaded blueberry anthocyanins

Micellar casein (MC) is a natural carrier for delivering various bioactive substances, and its gastrointestinal digestion behavior has an important impact on the loaded materials. Studies have shown that the digestion behavior of MC is dominated by colloidal calcium phosphate (CCP) in micelle structure. In this paper, The MCs with different CCP levels were used as the carriers to prepare spray-dried microparticles loaded with blueberry anthocyanins (ACNs), then the release of ACNs during digestion was investigated. The results found that the microparticles with less CCP showed the faster dissolution and quicker protein hydrolysis, which caused weaker curd ability. The coagulation was believed as the critical issue to influence the digestion and release behaviors. Therefore, lowering CCP resulted in significantly more ACNs released. This study demonstrated the possibility of using CCP levels to control MC digestion behaviors, which can further determine the release of loaded bioactive substances in casein-based delivery systems.

Comparison the effect of fruits extract with fungal protease on waffle quality

The purpose of this study was investigated the effect of kiwifruit and fig extracts contain of protease enzyme as a natural additives in comparison with fungal protease enzyme on the sensory and quality properties of waffle. It was done by use of the one- way ANOVA design for three independent variables including: kiwifruit extract and fig extract (0.03 and 0.05%) and fungal protease enzyme (0.003 and 0.005%). These results suggest that pH, moisture, firmness, dough consistency, density, color and texture of waffles were improved by the addition of fungal protease enzyme and kiwifruit extract in comparison with fig extract. The dough Consistency (cm) was reduced by using protease enzyme from 8.95 ± 0.92 to 19.75 ± 1.03. The moisture content and dough density was reduced by using protease enzyme and the minim moisture and dough density was at waffle with 0.05% kiwifruit. The color index, SEM, hardness and extensibility were improved by using 0.005% protease enzyme and 0.05% kiwi fruit extract. The highest sensory properties were at sample with 0.05% kiwi fruit extract. The result demonstrated that the addition of 0.05% kiwifruit extract improved the quality of the waffle, and could replace by fungal protease enzyme for reduce cost in production.

Clotting Properties of Onopordum tauricum (Willd.) Aqueous Extract in Milk of Different Species

Plant proteases used in cheesemaking are easily available and could increase the acceptability of cheeses, otherwise hindered by ethical issues (e.g., religions, dietary habits, aversion to genetically engineered food and food ingredients). The milk clotting potential of Onopordum tauricum (Willd.) aqueous extract as an alternative to animal rennet was assessed for the first time in milk of different species (ewe, goat, cow). Among the aerial anatomical parts, i.e., receptacle, leaves, stems, and flowers, only the latter ones showed clotting properties. A response surface methodology (RSM) was used to explore the effects of three independent variables (temperature, pH, volume of coagulant) on the milk clotting activity (MCA) of the flower extract. A second-order polynomial model adequately described the experimental data and predicted a temperature value of 55 °C, a pH value of 4.9–5.7, and a volume of coagulant of 300–500 μL (added to 5 mL of milk) as optimal conditions to maximize the MCA. At a 35 °C temperature and natural milk pH of 6.7–6.8, the estimated MCA of the O. tauricum extract was 72–87, 69–86, and 75–151, in goat’s, ewe’s, and cow’s milk, respectively. In comparison, the MCA of calf rennet was 5.4–4.9, 3.3–14.7, and 4.9–16.7 times higher than that of the plant extract in goat’s, ewe’s, and cow’s milk, respectively.

Nutraceutical and Technological Properties of Buffalo and Sheep Cheese Produced by the Addition of Kiwi Juice as a Coagulant

Kiwifruit is an interesting alternative to chymosin for milk coagulation. Although the clotting properties of actinidin (the proteolytic agent present in kiwi) have been widely investigated, little is known about the nutraceutical and organoleptic effects of kiwifruit on the characteristics of cheese. We investigated kiwifruit pulp, compared to calf rennet, in cheesemaking using sheep and buffalo milk. Although the kiwifruit extract showed a longer coagulation and syneresis time than calf rennet, it could nevertheless be exploited as a plant coagulant due to its positive effect on the nutraceutical properties. In fact, the sheep and buffalo cheese were higher in polyphenols and phytosterols than the cheese obtained using calf rennet. In addition, the nutraceutical properties were enhanced, with just a slight effect on the aroma of the cheese.

High-Level Expression and Substrate-Binding Region Modification of a Novel BL312 Milk-Clotting Enzyme To Enhance the Ratio of Milk-Clotting Activity to Proteolytic Activity

A novel BL312 milk-clotting enzyme (MCE) exhibited high-level expression and remarkable milk-clotting activity (MCA) (865 ± 20 SU/mL) that was 3.3-fold higher than the control by optimizing induction conditions in recombinant Escherichia. coli harboring pET24a-proMCE. Through substrate-binding region analyses and modification, MCE-G165A was identified from nine mutants and showed a proteolytic activity of 49.4 ± 2.4 U/mL and an MCA/PA ratio of 18.2, which were respectively 1.9-fold lower and 2.0-fold higher than those of the control. The purified MCE-G165A (28 kDa) exhibited weak α_s-casein, β-casein, and strong κ-casein (κ-CN) hydrolysis levels as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and reversed-phase high-performance liquid chromatography. The milk-clotting mechanism for MCE-G165A was the primary hydrolysis of Met106-Ala107 and Asn123-Thr124 bonds in κ-CN, as determined by mass spectrometry. MCE-G165A showed different hydrolysis sites in casein, leading to various functional peptides. Feasible methods for obtaining MCEs suitable as calf rennet substitutes are presented.

Purification and Biochemical Characterization of Cysteine Protease from Baby Kiwi (Actinidia arguta)

Background:

It has recently been reported that the fruit, stems and leaves ofActinidia argutahave various potential health effects including an antioxidant effect, anticancer effect, anti-allergic effect and α-glucosidase inhibitory effect. However, little is known about the biochemical properties of cysteine protease in the fruit juice ofA. arguta.

Methods:

Ion exchange chromatography to purify the cysteine protease from the fruit juice ofA. arguta, and some synthetic substrates to determinate the enzyme activity were used.

Results:

Cysteine protease was purified to homogeneity fromA. argutafruit juice by ion exchange chromatography. The molecular weight of the purified enzyme was calculated to be approximately 25,500 by SDS-PAGE in the presence of β-ME. The enzyme rapidly hydrolyzed the substrate Z-Leu-Arg-MCA and moderately hydrolyzed other substrates including Boc-Val-Leu-Lys-MCA, Z-Val-Val-Arg-MCA and Z-Phe-Arg-MCA. Kinetic parameters for these four substrates were determined. TheKm,Vmax,KcatandKcat/Kmvalues for Z-Leu-Arg-MCA, the most preferentially cleaved by the enzyme, were 100 μM, 63.8 μmoles/mg/min, 27.26 sec-1and 0.2726 sec-1μM-1, respectively. Furthermore, the activity of the enzyme was strongly inhibited by inhibitors including antipain, leupeptin, E-64, E-64c, kinin-free-LMW kininogen and cystatin C. Those biochemical data indicated that the enzyme was a cysteine protease. The amino acid sequence of the first 21 residues of cysteine protease purified fromActinidia argutawas Val1-Leu-Pro-Asp-Tyr5-Val-Asp-Trp-Arg-Ser10-Ala-Gly-Ala-Val-Val15-Asp-Ile-Lys-Ser-Qln20-Gly. This sequence showed high homology to the sequences of actinidin fromAcinidia deliciosa(95.0%) and actinidin fromActinidia eriantha(90%). These three cysteine proteases were thought to be common allied species.

Conclusion:

The biochemical properties of the enzyme purified fromA. argutafruit juice were determined. These basic data are expected to contribute to the maintenance and improvement of human health as well as to the promotion of protein digestion and absorption through its proteolytic functions.

Comparative analysis on the distribution of protease activities among fruits and vegetable resources

In this study, a comparative analysis on the distribution of protease activities among 90 plant resources, including fruits and vegetables, has been performed. Protease activities of plant extracts were assayed at different pH values (pH 3.0, pH 7.5 and pH 10.5) using casein as a substrate. Ten fruits and thirteen vegetables show protease activities above 10U/g. Pineapple, fig and papaya, which are used for commercial protease production, exhibited high protease activities. Additionally, high protease activities were detected in kiwifruit (28.8U/g), broccoli (16.9U/g), ginger (16.6U/g), leek (32.7U/g) and red pepper (15.8U/g) at different pH values. SDS-PAGE and zymograms confirmed that various types of proteases existed in the five plant extracts and might be explored. Furthermore, five plant extracts were treated by different protease inhibitors. These results show that there are still many plant resources unexplored, which may be promising candidates for plant-derived protease production.

Characterisation of general proteolytic, milk clotting and antifungal activity of Ficus carica latex during fruit ripening

BACKGROUND

The physiological role of fig latex is to protect the plant from pathogens. Latex is a rich source of proteases, predominantly ficin. Fig latex also contains collagenolytic protease and chitinolytic enzymes. Our aim was to investigate changes in protein composition, enzyme and antifungal activities of fig latex during fruit ripening.

RESULTS

Comparison of latex samples in different time periods showed a uniform increase of protein concentration in chronological order. The content of collagenolytic protease did not differ significantly in the latex samples, while the content of ficin decreased. Ficin-specific activity towards casein was the highest at the beginning of fruit development (about 80 U mg(-1)). Specific milk clotting activity increased as well as the abundance of casein band in the clots. Specific chitinolytic activity at the beginning of flowering was 6.5 times higher than the activity in the period when fruits are ripe. Antifungal activity is the most extensive in spring.

CONCLUSION

Ficin forms with different casein specificities are present in different proportions during fruit ripening, which is of importance for applications in the dairy industry. The protection mechanism against insects and fungi, which relies on chitinolytic activity, is the most important in the early phases of flowering and is replaced with other strategies over time.

High Milk-Clotting Activity Expressed by the Newly Isolated Paenibacillus spp. Strain BD3526

Paenibacillus spp. BD3526, a bacterium exhibiting a protein hydrolysis circle surrounded with an obvious precipitation zone on skim milk agar, was isolated from raw yak (Bos grunniens) milk collected in Tibet, China. Phylogenetic analysis based on 16S rRNA and whole genome sequence comparison indicated the isolate belong to the genus Paenibacillus. The strain BD3526 demonstrated strong ability to produce protease with milk clotting activity (MCA) in wheat bran broth. The protease with MCA was predominantly accumulated during the late-exponential phase of growth. The proteolytic activity (PA) of the BD3526 protease was 1.33-fold higher than that of the commercial R. miehei coagulant. A maximum MCA (6470 ± 281 SU mL⁻¹) of the strain BD3526 was reached under optimal cultivation conditions. The protease with MCA was precipitated from the cultivated supernatant of wheat bran broth with ammonium sulfate and purified by anion-exchange chromatography. The molecular weight of the protease with MCA was determined as 35 kDa by sodium dodecyl sulfate-polyacrylamide gels electrophoresis (SDS-PAGE) and gelatin zymography. The cleavage site of the BD3526 protease with MCA in κ-casein was located at the Met₁₀₆–Ala₁₀₇ bond, as determined by mass spectrometry analysis.