Biotechnological Applications of Proteases in Food Technology

Statistical optimisation of protease production using a freshwater bacterium Chryseobacterium cucumeris SARJS-2 for multiple industrial applications

Feathers, rich in keratin, are usually the unused by-products of poultry industries. In addition, the cast-off X-ray films serve as secondary sources of silver, and the traditional method of silver extraction from this source is costly and not eco-friendly. Therefore, the current study focuses on protease production using a freshwater bacterium Chryseobacterium cucumeris SARJS-2, aiming to convert these wastes into useful products. The protease production was optimized by one-factor-at-a-time (OFAT), followed by Plackett Burman design (PBD) and response surface methodology (RSM). The protease production got enhanced by more than two folds after the statistical optimisation. Upon partial purification, the enzyme activity increased by approximately three folds. The protease was active in the range of temperatures from 25 to 75 °C, but the optimum temperature was recorded as 35 °C. The protease exhibited detergent compatibility and organic solvent stability. The detergent compatibility suggests the protease could be a detergent additive. It was also found that the presence of Fe⁺² enhanced protease activity. The protease was tested for stain removal, feather degradation and silver recovery applications. It was found that the protease could efficiently remove stains of blood and tomato sauce. In addition, the protease was found to be a successful candidate for feather degradation, thereby feather-hydrolysate production which has prominent roles as nature-friendly fertilizer and animal feed ingredient. The protease also degraded gelatin from the X-ray films to release the silver-halides for silver recovery. The results recommend that the SARJS-2 protease is a potential candidate for use in eco-friendly applications in various industrial sectors.

Extraction and crosslinking of bromelain aggregates for improved stability and reusability from pineapple processing waste

The present study is first of its kind that focuses upon the extraction of bromelain from pineapple core waste and stabilising it as insoluble cross-linked aggregates. The influence of process variables such as the choice of precipitant, type of cross-linker, concentration of cross-linker and the reaction time for cross-linking step was investigated upon the activity recovery of bromelain cross-linked aggregates. The optimization of this biocatalyst preparation specifically recovered 87% of the enzymatic activity available in pineapple core waste by ammonium sulphate (60%, w/v) precipitation followed by cross-linking for 4 h with 80 mM glutaraldehyde. Cross-linked bromelain aggregates were thermally more stable and exhibited higher pH stability in comparison to free bromelain. The cross-linked bromelain aggregates exhibited higher operational stability in different organic solvents at 4 °C. The highest operational stability (% stability given in parenthesis) was observed in acetone (100%) followed by hexane (53.6%), ethyl acetate (39.6%), ethanol (32.5%) and chloroform (14.9%). The kinetic studies revealed higher Km value (5.45 mM) after the formation of cross-linked bromelain aggregates as compared to free bromelain (5.04 mM) with almost similar Vmax values. Cross-linked bromelain aggregates also showed significant reusability characteristics with an activity retention of >85% after 5-time cycles. Such recyclability of bromelain cross-linked aggregates could lead to potential industrial applications in both food and non-food sector. In addition, the present extraction method avoids costs related to purification and expensive immobilization carriers.

Glyoxyl-Activated Agarose as Support for Covalently Link Novo-Pro D: Biocatalysts Performance in the Hydrolysis of Casein

This study aimed to evaluate the performance of a commercial protease (Novo-Pro D (NPD)), both in soluble and immobilized forms, in the hydrolysis of proteins (using casein as model protein). Immobilization of the protease NPD on 6% agarose activated with glyoxyl groups for 24 h at 20 °C and pH 10.0 allowed preparing immobilized biocatalyst with around 90% immobilization yield, 92% recovered activity versus small substrate, and a thermal stability 5.3-fold higher than the dialyzed soluble enzyme at 50 °C and pH 8.0. Immobilization times longer than 24 h lead to a decrease in the recovered activity and did not improve the biocatalyst stability. At 50 °C and pH 6.5, the immobilized NPD was around 20-fold more stable than the dialyzed soluble protease. Versus casein, the immobilized NDP presented a 10% level of activity, but it allowed hydrolyzing casein (26 g/L) at 50 °C and pH 6.5 up to a 40% degree of hydrolysis (DH) after 2 h reaction, while under the same conditions, only a 34% DH was achieved with soluble NPD. In addition, the immobilized NPD showed good reusability, maintaining the DH of casein for at least ten 2h-reaction batches.

Biocatalysis in the winemaking industry: Challenges and opportunities for immobilized enzymes

Enzymes are powerful catalysts already being used in a large number of industrial processes. Impressive advantages in enzyme catalysts improvement have occurred in recent years aiming to improve their performance under harsh operation conditions far away from those of their cellular habitat. Production levels of the winemaking industry have experienced a remarkable increase, and technological innovations have been introduced for increasing the efficiency at different process steps or for improving wine quality, which is a key issue in this industry. Enzymes, such as pectinases and proteases, have been traditionally used, and others, such as glycosidases, have been more recently introduced in the modern wine industry, and many dedicated studies refer to the improvement of enzyme performance under winemaking conditions. Within this framework, a thorough review on the role of enzymes in winemaking is presented, with special emphasis on the use of immobilized enzymes as a significant strategy for catalyst improvement within an industry in which enzymes play important roles that are to be reinforced paralleling innovation.

H., Li YM, Wang YF, Liu YH, Lu FP. Evaluation of the site-unspecified peptide identification method for proteolytic peptide mapping

The site-unspecific method could successfully identify most of the peptides from tryptic hydrolysates revealed by site-specific identification.

Enhanced production of recombinant serratiopeptidase in Escherichia coli and its characterization as a potential biosimilar to native biotherapeutic counterpart

BACKGROUND

Serratia marcescens, a Gram-negative nosocomial pathogen secretes a 50 kDa multi-domain zinc metalloprotease called serratiopeptidase. Broad substrate specificity of serratiopeptidase makes it suitable for detergent and food processing industries The protein shows potent anti-inflammatory, anti-edemic, analgesic, antibiofilm activity and sold as an individual or fixed-dose enteric-coated tablets combined with other drugs. Although controversial, serratiopeptidase as drug is used in the treatment of chronic sinusitis, carpal tunnel syndrome, sprains, torn ligaments, and postoperative inflammation. Since the native producer of serratiopeptidase is a pathogenic microorganism, the current production methods need to be replaced by alternative approaches. Heterologous expression of serratiopeptidase in E. coli was tried before but not found suitable due to the limited yield, and other expression related issues due to its inherent proteolytic activity such as cytotoxicity, cell death, no expression, minimal expression, or inactive protein accumulation.

RESULTS

Recombinant expression of mature form serratiopeptidase in E. coli seems toxic and resulted in the failure of transformation and other expression related issues. Although E. coli C43(DE3) cells, express protein correctly, the yield was compromised severely. Optimization of protein expression process parameters such as nutrient composition, induction point, inducer concentration, post-induction duration, etc., caused significant enhancement in serratiopeptidase production (57.9 ± 0.73% of total cellular protein). Expressed protein formed insoluble, enzymatically inactive inclusion bodies, and gave 40-45 mg/l homogenous (> 98% purity) biologically active and conformationally similar serratiopeptidase to the commercial counterpart upon refolding and purification.

CONCLUSION

Expression of mature serratiopeptidase in E. coli C43(DE3) cells eliminated the protein expression associated with toxicity issues. Further optimization of process parameters significantly enhanced the overexpression of protein resulting in the higher yield of pure and functionally active recombinant serratiopeptidase. The biological activity and conformational features of recombinant serratiopeptidase were very similar to the commercially available counterpart suggesting it-a potential biosimilar of therapeutic and industrial relevance.

Kinetic and thermodynamic properties of purified alkaline protease from Bacillus pumilus Y7 and non-covalent immobilization to poly(vinylimidazole)/clay hydrogel

The characterization of the hydrogel was performed using Fourier‐transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy. Purified Bacillus pumilus Y7‐derived alkaline protease was immobilized in Poly (vinylimidazole)/clay (PVI/SEP) hydrogel with 95% yield of immobilization. Immobilization decreased the pH optimum from 9 to 6 for free and immobilized enzyme, respectively. Temperature optimum 3°C decreased for immobilized enzyme. The K_m, V_m, and k_cat of immobilized enzyme were 4.4, 1.7, and 7.5‐fold increased over its free counterpart. Immobilized protease retained about 65% residual activity for 16^th reuse. The immobilized protease endured its 35% residual activity in the material after six cycle's batch applications. The results of thermodynamic analysis for casein hydrolysis showed that the ΔG^≠ (activation free energy) and ΔG^≠_E‐T (activation free energy of transition state formation) obtained for the immobilized enzyme decreased in comparison to those obtained for the free enzyme. On the other hand, the value of ΔG^≠_ES (free energy of substrate binding) was observed to have increased. These results indicate an increase in the spontaneity of the biochemical reaction post immobilization. Enthalpy value of immobilized enzyme that was 2.2‐fold increased over the free enzyme indicated lower energy for the formation of the transition state, and increased ΔS^≠ value implied that the immobilized form of the enzyme was more ordered than its free form.

Noni (Morinda citrifolia L.) fruit as a new source of milk-clotting cysteine proteases

This work reports the characterisation of caseinolytic and milk-clotting activities of proteases extracted from ripe fruits of Morinda citrifolia L., as a potential of their use in cheese production. Noni puree extract (NPE) was obtained by homogenising the fresh puree in 150 mM NaCl/50 mM sodium phosphate buffer (pH 7.0). The resulting protein concentration was of 0.367 ± 0.006 mg/mL, and an electrophoretic profile of the extract revealed protein bands ranging from 14 to 55 kDa. The proteolytic activity of NPE was higher when the extract had been previously incubated at pH 6.0 (8.859 ± 0.216 U/mg), whereas the optimum caseinolytic activity was observed at 50 °C. Noni puree proteases were strongly (98%) inhibited by iodoacetamide and E-64, suggesting the presence of only cysteine proteases in the crude extract. NPE proteases showed a milk-clotting activity (MCA) of 238.80 ± 5.29 U/mL, a specific milk-clotting activity (SMCA) of 9950.17 ± 220.74 U/mg, and an SMCA/PA ratio of 1124.31 ± 24.94, this last being comparable to those of commercial calf rennet. The cheese manufactured using NPE presented brittle and soft texture, high humidity, and showed sanitary conditions compatible with current Brazilian regulations. The product showed a slightly bitter taste, but still good acceptability, rating between 6 and 7 in the hedonic scale for flavour, texture, and overall acceptance. Lastly, there was 60% of positive purchase intent, demonstrating that noni fruit is a promising source of milk-clotting enzymes for the dairy industry.

Microbial Proteases Applications

The use of chemicals around the globe in different industries has increased tremendously, affecting the health of people. The modern world intends to replace these noxious chemicals with environmental friendly products for the betterment of life on the planet. Establishing enzymatic processes in spite of chemical processes has been a prime objective of scientists. Various enzymes, specifically microbial proteases, are the most essentially used in different corporate sectors, such as textile, detergent, leather, feed, waste, and others. Proteases with respect to physiological and commercial roles hold a pivotal position. As they are performing synthetic and degradative functions, proteases are found ubiquitously, such as in plants, animals, and microbes. Among different producers of proteases, Bacillus sp. are mostly commercially exploited microbes for proteases. Proteases are successfully considered as an alternative to chemicals and an eco-friendly indicator for nature or the surroundings. The evolutionary relationship among acidic, neutral, and alkaline proteases has been analyzed based on their protein sequences, but there remains a lack of information that regulates the diversity in their specificity. Researchers are looking for microbial proteases as they can tolerate harsh conditions, ways to prevent autoproteolytic activity, stability in optimum pH, and substrate specificity. The current review focuses on the comparison among different proteases and the current problems faced during production and application at the industrial level. Deciphering these issues would enable us to promote microbial proteases economically and commercially around the world.

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.

Cooperativity of covalent attachment and ion exchange on alcalase immobilization using glutaraldehyde chemistry: Enzyme stabilization and improved proteolytic activity

Alcalase was scarcely immobilized on monoaminoethyl-N-aminoethyl (MANAE)-agarose beads at different pH values (<20% at pH 7). The enzyme did not immobilize on MANAE-agarose activated with glutaraldehyde at high ionic strength, suggesting a low reactivity of the enzyme with the support functionalized in this manner. However, the immobilization is relatively rapid when using low ionic strength and glutaraldehyde activated support. Using these conditions, the enzyme was immobilized at pH 5, 7, and 9, and in all cases, the activity vs. Boc-Ala-ONp decreased to around 50%. However, the activity vs. casein greatly depends on the immobilization pH, while at pH 5 it is also 50%, at pH 7 it is around 200%, and at pH 9 it is around 140%. All immobilized enzymes were significantly stabilized compared to the free enzyme when inactivated at pH 5, 7, or 9. The highest stability was always observed when the enzyme was immobilized at pH 9, and the worst stability occurred when the enzyme was immobilized at pH 5, in agreement with the reactivity of the amino groups of the enzyme. Stabilization was lower for the three preparations when the inactivation was performed at pH 5. Thus, this is a practical example on how the cooperative effect of ion exchange and covalent immobilization may be used to immobilize an enzyme when only one independent cause of immobilization is unable to immobilize the enzyme, while adjusting the immobilization pH leads to very different properties of the final immobilized enzyme preparation. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2768, 2019.

Protease-based cross-linked enzyme aggregates with improved catalytic stability, silver removal, and dehairing potentials

Proteases have gained special research place due to their broader activity spectrum and applied perspectives for different industrial sectors. The present research focused on three aims, i.e., (1) to identify the best protease producer strain among three different Aspergillus strains, (2) the development of protease-based cross-linked enzyme aggregates (CLEAs) and (3) silver removal and dehairing potentialities of developed CLEAs. A. flavus gave optimum activity (98.50 U/mL) with the culture conditions (pH -7.5, 35 °C, inoculum 2.5 mL and fermentation time 48 h) by applying RSM under CCD. The protease-CLEAs were developed with recovery activity (37.45%) by optimizing conditions through RSM under CCD (80% ammonium sulfate, 65 mM glutaraldehyde, and 0.15 mM BSA). The adequacy of the model was checked by ANOVA, and the interactions among different variables were plotted using 3-D graphs. The characterization profile revealed high pH and thermal stability at pH -9 and 60 °C, respectively. The kinetic study revealed lower K_M and higher V_max values (31.02 μM and 91.16 U/mL, respectively) after CLEAs formation, as compared to the free protease (61.42 μM and 84.45 U/mL, respectively). By applying on X-ray film and animal hides, protease-CLEAs showed the best activity with minimum time as compared to free protease.

Production and Characterization of an Extracellular Acid Protease from Thermophilic Brevibacillus sp. OA30 Isolated from an Algerian Hot Spring

Proteases have numerous biotechnological applications and the bioprospection for newly-thermostable proteases from the great biodiversity of thermophilic microorganisms inhabiting hot environments, such as geothermal sources, aims to discover more effective enzymes for processes at higher temperatures. We report in this paper the production and the characterization of a purified acid protease from strain OA30, a moderate thermophilic bacterium isolated from an Algerian hot spring. Phenotypic and genotypic study of strain OA30 was followed by the production of the extracellular protease in a physiologically-optimized medium. Strain OA30 showed multiple extracellular proteolytic enzymes and protease 32-F38 was purified by chromatographic methods and its biochemical characteristics were studied. Strain OA30 was affiliated with Brevibacillus thermoruber species. Protease 32-F38 had an estimated molecular weight of 64.6 kDa and was optimally active at 50 °C. It showed a great thermostability after 240 min and its optimum pH was 6.0. Protease 32-F38 was highly stable in the presence of different detergents and solvents and was inhibited by metalloprotease inhibitors. The results of this work suggest that protease 32-F38 might have interesting biotechnological applications.