Trypsin from zebra blenny (Salaria basilisca) viscera: Purification, characterisation and potential application as a detergent additive

Recovery of alkaline proteinases from fisheries wastes: biochemical characterization and applications

Fish visceral waste, which is normally discarded, is considered one of the richest sources of proteinases with potential biotechnological applications. For this reason, alkaline proteinases from viscera of Argentine hake Merluccius hubbsi, Brazilian flathead Percophis brasiliensis, Brazilian codling Urophycis brasiliensis, and stripped weakfish Cynoscion guatucupa were characterized. Individuals were caught by a commercial fleet off the coast of the Argentinean Sea. The intestine and pyloric caeca were dissected out and then minced and triturated with distilled water. The proteinase activity of P. brasiliensis extracts was enhanced by all the ions tested (Mn2+, K+, Na+, Ca+2) while the enzymes of the other species were stable in the presence of those ions, retaining more than 60% of their enzymatic activity. Alkaline proteinases of all species showed extreme stability to 5% v/v surfactants at 60 min (Sodium dodecyl sulfate, Triton X-100, Tween 20, Tween 80), and relative stability toward an 6% v/v oxidizing agent (H2O2) and organic solvents 80% (acetone, isopropanol, methanol, ethanol). The enzyme extracts were incubated for 60 min with these compounds. Interestingly, alkaline proteinases from all species were compatible with the commercial detergents (Ala, Skip, and Ace). These results demonstrate that proteinases recovered from a no-cost sample such as fishery residues can be used for industrial applications, such as detergent formulations.

Development of an effective method for purifying trypsin using a recombinant inhibitor

A trypsin affinity material was prepared by covalently immobilizing buckwheat trypsin inhibitor (BTI) on epichlorohydrin-activated cross-linked agarose gel (Selfinose CL 6 B). The optimal conditions for activating Selfinose CL 6 B were 15 % epichlorohydrin and 0.8 M NaOH at 40 °C for 2 h. The optimal pH for immobilizing BTI was 9.5. BTI-Sefinose CL 6 B showed a maximum adsorption capacity of 2.25 mg trypsin/(g support). The material also displayed good reusability, retaining over 90 % of its initial adsorption capacity after 30 cycles. High-purity trypsin was obtained from locust homogenate using BTI-Selfinose CL 6 B through one-step affinity chromatography. The molecular mass and Km value of locust trypsin were determined as 27 kDa and 0.241 mM using N-benzoyl-DL-arginine-nitroanilide as substrate. The optimal temperature and pH of trypsin activity were 55 °C and 9.0, respectively. The enzyme exhibited good stability in the temperature range of 30-50 °C and pH range of 4.0-10.0. BTI-Selfinose CL 6 B demonstrates potential application in the preparation of high-purity trypsin and the discovery of more novel trypsin from various species.

Preparation of micron-sized benzamidine-modified magnetic agarose beads for trypsin purification from fish viscera

The effective method for trypsin purification should be established because trypsin has important economic value. In this work, a novel and simple strategy was proposed for fabricating micron-sized magnetic Fe3O4@agarose-benzamidine beads (MABB) with benzamidine as a ligand, which can efficiently and selectively capture trypsin. The micro-sized MABB, with clear spherical core-shell structure and average particle size of 6.6 μm, showed excellent suspension ability and magnetic responsiveness in aqueous solution. The adsorption capacity and selectivity of MABB towards target trypsin were significantly better than those of non-target lysozyme. According to the Langmuir equation, the maximum adsorption capacity of MABB for trypsin was 1946 mg g-1 at 25 °C, and the adsorption should be a physical sorption process. Furthermore, the initial adsorption rate and half equilibrium time of MABB toward trypsin were 787.4 mg g-1 min-1 and 0.71 min, respectively. To prove the practicability, MABB-based magnetic solid-phase extraction (MSPE) was proposed, and the related parameters were optimized in detail to improve the purification efficiency. With Tris-HCl buffer (50 mM, 10 mM CaCl2, pH 8.0) as extraction buffer, Tris-HCl buffer (50 mM, 100 mM CaCl2, pH 8.0) as rinsing buffer, acidic eluent (0.01 M HCl, 0.5 M NaCl, pH 2.0) as eluent buffer and alkaline buffer (1 M Tris-HCl buffer, pH 10.0) as neutralization solution, the MABB-based MSPE was successfully used for trypsin purification from the viscera of grass carp (Ctenopharyngodon idella). The molecular weight of purified trypsin was determined as approximate 23 kDa through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The purified trypsin was highly active from 30 °C to 60 °C, with an optimum temperature of 50 °C, and was tolerant to pH variation, exhibiting 85 % of maximum enzyme activity from pH 7.0 to 10.0. The results demonstrated that the proposed MABB-based MSPE could effectively purify trypsin and ensure the biological activity of purified trypsin. Therefore, we believe that the novel MABB could be applicable for efficient purification of trypsin from complex biological systems.

Adaptability to the environment of protease by secondary structure changes and application to enzyme-selective hydrolysis

The reactions involving enzymes are significantly influenced by various environmental factors. Clarity of how the activity and structure of proteases impact their function is crucial for more efficient application of enzymes as a tool. The impact of temperature, pH, and ionic strength on changes in protease activity, secondary structure, and protein conformation during enzymatic hydrolysis were investigated in this study. The enzymatic activity and secondary structure of acid-base protease were found to undergo significant modifications under different physical conditions, as demonstrated by UV spectrophotometry and FTIR spectroscopy analysis. Specifically, variations in α-helix and β-fold content were observed to correlate with changes in enzyme activity. Molecular simulation analysis revealed that physical conditions have varying effects on the protease, particularly influencing enzyme activity and secondary structure. Evaluation of the proteases indicated alterations in both enzyme activity and structure. This treatment selectively hydrolyzed β-lactoglobulin and reduced sensitization. These findings offer novel perspectives on the functionalities and regulatory mechanisms of proteases, as well as potential industrial applications.

Enzymes from Fishery and Aquaculture Waste: Research Trends in the Era of Artificial Intelligence and Circular Bio-Economy

In the era of the blue bio-economy, which promotes the sustainable utilization and exploitation of marine resources for economic growth and development, the fisheries and aquaculture industries still face huge sustainability issues. One of the major challenges of these industries is associated with the generation and management of wastes, which pose a serious threat to human health and the environment if not properly treated. In the best-case scenario, fishery and aquaculture waste is processed into low-value commodities such as fishmeal and fish oil. However, this renewable organic biomass contains a number of highly valuable bioproducts, including enzymes, bioactive peptides, as well as functional proteins and polysaccharides. Marine-derived enzymes are known to have unique physical, chemical and catalytic characteristics and are reported to be superior to those from plant and animal origins. Moreover, it has been established that enzymes from marine species possess cold-adapted properties, which makes them interesting from technological, economic and sustainability points of view. Therefore, this review centers around enzymes from fishery and aquaculture waste, with a special focus on proteases, lipases, carbohydrases, chitinases and transglutaminases. Additionally, the use of fishery and aquaculture waste as a substrate for the production of industrially relevant microbial enzymes is discussed. The application of emerging technologies (i.e., artificial intelligence and machine learning) in microbial enzyme production is also presented.

Characterization and Hydrolysis Mechanism Analysis of a Cold-Adapted Trypsin-Like Protease from Antarctic Krill

Cold-adapted proteases are capable of efficient protein hydrolysis at reduced temperatures, which offer significant potential applications in the area of low temperature food processing. In this paper, we attempted to characterize cold-adapted proteases from Antarctic krill. Antarctic krill possesses an extremely active autolytic enzyme system in their bodies, and the production of peptides and free amino acids accompanies the rapid breakdown of muscle proteins following the death. The crucial role of trypsin in this process is recognized. A cold-adapted trypsin named OUC-Pp-20 from Antarctic krill genome was cloned and expressed in Pichia pastoris. Recombinant trypsin is a monomeric protein of 26.8 ± 1.0 kDa with optimum reaction temperature at 25 °C. In addition, the catalytic specificity of OUC-Pp-20 was assessed by identifying its hydrolysis sites through LC-MS/MS. OUC-Pp-20 appeared to prefer Gln and Asn at the P1 position, which is an amino acid with an amide group in its side chain. Hydrolysis reactions on milk and shrimp meat revealed that it can effectively degrade allergenic components in milk and arginine kinase in shrimp meat. These findings update the current knowledge of cold-adapted trypsin and demonstrate the potential application of OUC-Pp-20 in low temperature food processing.

Enhanced expression of a novel trypsin from Streptomyces fradiae in Komagataella phaffii GS115 through combinational strategies of propeptide engineering and self-degredation sites modification

This study aimed to enhance the expression level of a novel trypsin gene from Streptomyces fradiae ATCC14544 in Komagataella phaffii GS115 through the combinational use of propeptide engineering and self-degradation residues modification strategies. An artificial propeptide consisted of thioredoxin TrxA, the bovine propeptide DDDDK and the hydrophobic peptide FVEF was introduced to replace the original propeptide while the self-degradation residue sites were predicted and analyzed through alanine screening. The results showed that the quantity and enzymatic activity of asft with engineered propeptide reached 47.02 mg/mL and 33.9 U/mL, which were 9.6 % and 59.29 % higher than those of wild-type (42.9 mg/mL and 13.8 U/mL). Moreover, the introduction of R295A/R315A mutation further enhanced the enzymatic activity (58.86 U/mL) and obviously alleviated the phenomena of self-degradation. The tolerance of trypsin towards alkaline environment was also improved since the optimal pH was shifted from pH 9.0 to pH 9.5 and the half-life value at pH 10 was significantly extended. Finally, the fermentation media composition and condition were optimized and trypsin activity in optimal condition reached 160.58 U/mL, which was 2.73-fold and 11.64-fold of that before optimization or before engineering. The results obtained in this study indicated that the combinational use of propeptide engineering and self-degradation sites modification might have great potential application in production of active trypsins.

Trypsin from Pyloric Caeca of Asian Seabass: Purification, Characterization, and Its Use in the Hydrolysis of Acid-Soluble Collagen

The study aimed to purify trypsin from the pyloric caeca of Asian seabass (Lates calcarifer), and investigate its proteolytic capability toward acid-soluble collagen (ASC) in comparison with commercial porcine trypsin (CPT). Trypsin was purified from pyloric caeca, a leftover from the evisceration process, via ammonium sulphate (40-60% saturation) precipitation, and a soybean trypsin inhibitor (SBTI)-Sepharose 4B column. A 18.5-fold purification and a yield of 15.2% were obtained. SDS-PAGE analysis confirmed a single band of trypsin with a molecular weight of 23.5 kDa. Purified trypsin also showed the single band in native-PAGE. The optimal pH and temperature of trypsin for BAPNA (the specific substrate for amidase) hydrolysis were 8.5 and 60 °C, respectively. The trypsin was stable within the pH range of 7.0-9.5 and temperature range of 25-55 °C. Protease inhibition study confirmed that the purified enzyme was trypsin. The purified trypsin had a Michaelis-Menten constant (Km) and catalytic constant (kcat) of 0.078 mM and 5.4 s-1, respectively, when BAPNA was used. For the hydrolysis of TAME (the specific substrate for esterase), the Km and Kcat were 0.09 mM and 4.8 s-1, respectively. Partially purified seabass trypsin (PPST) had a slightly lower hydrolysis capacity toward ASC than CPT, as evidenced by the lower degree of hydrolysis and protein degradation when the former was used. Both the α-chain and β-chain became more degraded as the hydrolysis time increased. Based on MALDI-TOP, peptides with MW of 2992-2970 Da were dominant in the hydrolysates. Therefore, seabass trypsin could be used in the production of hydrolyzed collagen. It could have economic importance to the market, by replacing some commercial proteases, which have religious constraints.

Physicochemical and Biochemical Properties of Trypsin-like Enzyme from Two Sturgeon Species

This work aimed to determine the physicochemical and biochemical properties of trypsin from beluga Huso huso and sevruga Acipenser stellatus, two highly valuable sturgeon species. According to the results obtained from the methods of casein-zymogram and inhibitory activity staining, the molecular weight of trypsin for sevruga and beluga was 27.5 and 29.5 kDa, respectively. Optimum pH and temperature values for both trypsins were recorded at 8.5 and 55 °C by BAPNA (a specific substrate), respectively. The stability of both trypsins was well-preserved at pH values from 6.0 to 11.0 and temperatures up to 50 °C. TLCK and SBTI, two specific trypsin inhibitors, showed a significant inhibitory effect on the enzymatic activity of both trypsins (p < 0.05). The enzyme activity was significantly increased in the presence of Ca⁺² and surfactants and decreased by oxidizing agents, Cu⁺², Zn⁺², and Co⁺² (p < 0.05). However, univalent ions Na⁺ and K⁺ did not show any significant effect on the activity of both trypsins (p > 0.05). The results of our study show that the properties of trypsin from beluga and sevruga are in agreement with data reported in bony fish and can contribute to the clear understanding of trypsin activity in these primitive species.

Fish By-Products: A Source of Enzymes to Generate Circular Bioactive Hydrolysates

Fish viscera are usually discarded as waste, causing environmental problems, or as low-value by-products. This study describes a self-sufficient and zero waste approach to obtain enzymes and protein hydrolysates from fish by-products. Firstly, recovery steps of viscera enzymatic extract were applied, and the resulting raw extract was stable at a pH range of 8-9 and at temperatures between 40 and 50 °C. The application of the extracted enzymes and alcalase on fish by-products hydrolysis was also determined. The selected conditions for the enzymatic hydrolysis were 10% (E/S) for 6 h using viscera enzymatic extract and 3% (E/S) for 2 h using alcalase. Fish protein hydrolysates (FPH) proved to have a notable antioxidant capacity with similar activity, ~11 mg ascorbic acid/g dry extract (ABTS assay) and ~150 mg Trolox/g dry extract (ORAC assay). FPH were also able to inhibit the angiotensin-converting enzyme, however, alcalase hydrolysates revealed a higher antihypertensive potential, IC₅₀ of 101 µg of protein/mL. In general, FPH obtained by both enzymes systems maintained these bioactivities after the passage throughout a simulated gastrointestinal tract. The hydrolysates also displayed important technological properties, namely oil absorption capacity (~1 g oil/g sample) and emulsifying property (~40%). Therefore, it will be conceivable to use fish by-products based on a circular economy approach to generate added value compounds for animal and human nutrition.

Identification of New Amylolytic Enzymes from Marine Symbiotic Bacteria of Bacillus Species

α-amylases are one of the most common and important industrial enzymes widely used in various industries. The present study was conducted with the aim of isolating and identifying symbiotic α-amylase enzyme-producing bacteria in the intestine of Silago Sihama and Rasterliger Canagorta fish living in Qeshm Island, Hormozgan. The intestinal symbiotic bacteria of these species were isolated using nutrient agar culture medium; then, α-amylase producing bacteria were screened using a special culture medium containing starch and the Lugol’s solution test. The α-amylase enzyme activity of enzyme-producing bacteria was measured using the starch substrate. Finally, bacteria with the highest enzyme activity were selected and identified by the 16S rRNA gene sequence analysis. The results showed that out of 22 isolated bacteria, 10 were able to grow in a special culture medium, and 5 strains of these 10 bacteria had the ability to produce relatively stronger halos. The four bacterial strains belonging to the genus Bacillus that had the highest α-amylase enzyme activity were identified and registered in the NCBI gene database as B. subtilis strains HR13, HR14, HR15, and HR16. Among these four strains, two strains of B. subtilis, HR13 and HR16, displayed high enzyme activity and maximum activity at 60 °C at pH values of 5 and 7, respectively. α-Amylase enzymes isolated from marine symbiotic bacteria of Bacillus species can be considered potential candidates for application in various industries.

Sustainable Upcycling of Fisheries and Aquaculture Wastes Using Fish-Derived Cold-Adapted Proteases

The fisheries and aquaculture industries are some of the major economic sectors in the world. However, these industries generate significant amounts of wastes that need to be properly managed to avoid serious health and environmental issues. Recent advances in marine waste valorization indicate that fish waste biomass represents an abundant source of high-value biomolecules including enzymes, functional proteins, bioactive peptides, and omega-3 rich oils. Enzyme-assisted processes, for the recovery of these value-added biomolecules, have gained interest over chemical-based processes due to their cost-effectiveness as well as their green and eco-friendly aspects. Currently, the majority of commercially available proteases that are used to recover value-added compounds from fisheries and aquaculture wastes are mesophilic and/or thermophilic that require significant energy input and can lead to unfavorable reactions (i.e., oxidation). Cold-adapted proteases extracted from cold-water fish species, on the other hand, are active at low temperatures but unstable at higher temperatures which makes them interesting from both environmental and economic points of view by upcycling fish waste as well as by offering substantial energy savings. This review provides a general overview of cold-adapted proteolytic enzymes from cold-water fish species and highlights the opportunities they offer in the valorization of fisheries and aquaculture wastes.

Digestive proteinases from the marine fish processing wastes of the South-West Atlantic Ocean: Their partial characterization and comparison

Fish processing generates plenty of waste that is directly discarded in open-air dumps and water sources, or treated in the same way as urban solid waste, causing serious pollution problems. The waste represents a significant source of high-value bioproducts with potential applications in different industrial processes such as the production of feed, fertilizers, biodiesel and biogas, detergent additives and cosmetics. The objective of this study was to characterize and compare specific activities under different pH values and temperature conditions of acid and alkaline proteinases and viscera yield from the following fish species: Argentine hake Merluccius hubbsi, Brazilian flathead Percophis brasiliensis, Brazilian codling Urophycis brasiliensis and Stripped weakfish Cynoscion guatucupa. Individuals were fished off the coast of Mar del Plata (Argentina) by a commercial fleet and the viscera were immediately extracted and kept on ice until use. Stomach proteinases from four species had the highest activity at pH 2, with stability in the range of pH 2-4. The optimum pH was 11.5 from intestinal enzymes of C. guatucupa, M. hubbsi and P. brasiliensis and 9.5 from intestinal enzymes of U. brasiliensis. Alkaline proteinases from all species were highly stable in the range of 7-11.5. The optimum temperature of stomach proteinases from the four species studied were 30 and 50°C, with stability at 10 and 30°C during 150 min. The optimum temperature of intestinal enzymes from the tested species were 50°C with high stability at 10 and 30°C during 150 min. Alkaline proteinase from all species and acid proteinases from C. guatucupa were inactive at 70°C after 150 min, while there was a residual activity lower than 5% at 80°C on pre-incubated stomach enzymes of M.hubbsi, P. brasiliensis and U. brasiliensis after 5, 10 and 20 min, respectively. Digestive proteinases recovered in this study could be appropriate for technological usage, reducing manufacturing costs, obtaining revenue from fishery wastes, and contributing to the reduction of environmental pollution.

Production of Protein Hydrolysates Using Marine Catfish Bagre panamensis Muscle or Casein as Substrates: Effect of Enzymatic Source and Degree of Hydrolysis on Antioxidant and Biochemical Properties

Protein hydrolysates from fishery byproducts have resulted to be nutraceutical ingredients with potential to be applied in human nutrition; however, critical quality attributes are dependent on some process parameters such as enzyme source and degree of hydrolysis. This study analyzed the biochemical properties and in vitro antioxidant activity (using DPPH, ABTS, and FRAP assays), of protein hydrolysates at 10, 20, and 30% degree of hydrolysis (DH), measured by pH-STAT and prepared from sea catfish (Bagre panamensis) muscle and casein as protein sources by treatment with alcalase (ALC) and a semi-purified protease extract (SPE) from B. panamensis intestinal tissues as enzyme sources. With SPE, the DH was reached faster than ALC regardless of the protein substrate used. Sea catfish muscle (MUSC) hydrolysate made with SPE at 30% DH showed the highest antioxidant activity (DPPH: 118.8 μmoles TE/mg; ABTS: EC50 of 1.5 mg/mL). In FRAP assay, the MUSC hydrolysates produced with SPE or ALC at 20% DH showed the higher activity (0.38 and 0.40 μmoles TE/mg, respectively). MUSC hydrolysates made with SPE contained the highest proportion of peptides with MW < 1.35 kDa and had a high protein content (72 to 78%), and almost 50% of the amino acids were essential. These results suggest that intestinal proteases and muscle of marine catfish represent a potential source to elaborate antioxidant protein hydrolysates. Our results promote the full utilization of this fish species and offer a biotechnological strategy for the management and valorization of its byproducts.

Identification of a novel alkaline serine protease from gazami crab (Portunus trituberculatus) hepatopancreas and its hydrolysis of myofibrillar protein

Serine proteases are thought to play a key role in the muscle softening of gazami crab (Portunus trituberculatus) during storage. A serine protease, Pt-sp2, was purified from the hepatopancreas of gazami crab using ammonium sulfate precipitation, anion-exchange and gel filtration chromatography, and was analyzed by mass spectrometry, transcriptome and bioinformatics. It revealed that Pt-sp2 was trypsin-like, with no 100% identical proteins in the NCBI database. The molecular weight of Pt-sp2 was approximately 37.2 kDa. Its optimum pH and temperature were 9.0 and 50 °C, respectively, using t-Butyloxy‑carbonyl-Phe-Ser-Arg-4-methyl-coumaryl-7-amide as a substrate. Pt-sp2 was activated in the presence of Ca²⁺. Both soybean trypsin inhibitor and Nα-Tosyl-l-lysine chloromethyl ketone hydrochloride completely suppressed Pt-sp2 activity, while it was only partially inhibited by phenylmethylsulfonyl fluoride and EDTA. However, PMSF, Pepstatin A and cystatin inhibitor E-64 showed no inhibition on Pt-sp2 protease activity. The Km value of Pt-sp2 was 0.82 μM, and Pt-sp2 effectively hydrolyzed myofibrillar protein at 37 °C.

Fish trypsins: potential applications in biomedicine and prospects for production

In fishes, trypsins are adapted to different environmental conditions, and the biochemical and kinetic properties of a broad variety of native isoforms have been studied. Proteolytic enzymes remain in high demand in the detergent, food, and feed industries; however, our analysis of the literature showed that, in the last decade, some fish trypsins have been studied for the synthesis of industrial peptides and for specific biomedical uses as antipathogenic agents against viruses and bacteria, which have been recently patented. In addition, innovative strategies of trypsin administration have been studied to ensure that trypsins retain their properties until they exert their action. Biomedical uses require the production of high-quality enzymes. In this context, the production of recombinant trypsins is an alternative. For this purpose, E. coli-based systems have been tested for the production of fish trypsins; however, P. pastoris-based systems also seem to show great potential in the production of fish trypsins with higher production quality. On the other hand, there is a lack of information regarding the specific structures, biochemical and kinetic properties, and characteristics of trypsins produced using heterologous systems. This review describes the potential uses of fish trypsins in biomedicine and the enzymatic and structural properties of native and recombinant fish trypsins obtained to date, outlining some prospects for their study.

Two trypsin isoforms from albacore tuna (Thunnus alalunga) liver: Purification and physicochemical and biochemical characterization

Two trypsins (A and B) from the liver of albacore tuna (Thunnus alalunga) were purified to homogeneity using a series of column chromatographies including Sephacryl S-200, Sephadex G-50 and Diethylaminoethyl-cellulose. Purity was increased to 80.35- and 101.23-fold with approximately 3.1 and 19.2% yield for trypsins A and B, respectively. The molecular weights of trypsins A and B were estimated to be 21 and 24kDa, respectively, by SDS-PAGE and size exclusion chromatography. Both trypsins showed only one band on native-PAGE. Trypsins A and B exhibited the maximal activity at 60°C and 55°C, respectively, and had the same optimal pH at 8.5 using N^α-p-Tosyl-l-arginine methyl ester hydrochloride (TAME) as a substrate. Stabilities of both trypsins were well maintained at a temperature up to 50°C and in the pH range of 7.0-11.0 and were highly dependent on the presence of calcium ion. The inhibition test demonstrated strong inhibition by soybean trypsin inhibitor and TLCK. Activity of both trypsins continuously decreased with increasing NaCl concentration (0-30%). The N-terminal amino acid sequence of 20 residues of the two trypsin isoforms had homology when compared to those of other fish trypsins.

Characterization of protease and effects of temperature and salinity on the biochemical changes during fermentation of Antarctic krill

BACKGROUND

Despite their abundance, Antarctic krill are underutilized because of numerous difficulties in their commercial processing. Ideally, fermentation technology can be applied to transform them into a popular condiment. In addition to the exploration of protease properties, the present study aimed to evaluate proteinase activity, pH, amino nitrogen, and histamine formation during fermentation at different temperatures and salt treatments.

RESULTS

Even though the activity of Antarctic krill protease reached a maximum at 40 °C and pH 7, it was stable at 30 °C and pH 7-9. Among the metal ions tested, Ca²⁺ , Mg²⁺ and K⁺ increased protease activity, in contrast to Zn²⁺ and Cu²⁺ . Within each treatment, the highest protease activity and amino nitrogen content, as well as the lowest histamine level, were observed on day 12 of fermentation. Treatment at 35 °C with 180 g kg^-1 salt led to the production of maximum amino nitrogen (0.0352 g kg^-1 ) and low histamine (≤0.0497 g kg^-1 ).

CONCLUSION

Krill paste fermented for 12 days at 35 °C with 180 g kg^-1 salt exhibited the optimal quality and properties, suggesting an efficient method for fermentation of Antarctic krill and other aquatic resources. © 2017 Society of Chemical Industry.

Trypsin purification using magnetic particles of azocasein-iron composite

This work presents an inexpensive, simple and fast procedure to purify trypsin based on affinity binding with ferromagnetic particles of azocasein composite (mAzo). Crude extract was obtained from intestines of fish Nile tilapia (Oreochromis niloticus) homogenized in buffer (01g tissue/ml). This extract was exposed to 100mg of mAzo and washed to remove unbound proteins by magnetic field. Trypsin was leached off under high ionic strength (3M NaCl). Preparation was achieved containing specific activity about 60 times higher than that of the crude extract. SDS-PAGE showed that the purified protein had molecular weight (24kDa) in concordance with the literature for the Nile tilapia trypsin. The mAzo composite can be reused and applied to purify trypsin from other sources.

Purification and characterization of trypsin from Luphiosilurus alexandri pyloric cecum

Trypsin from L. alexandri was purified using only two purification processes: ammonium sulfate precipitation and anion exchange liquid chromatography in DEAE-Sepharose. Trypsin mass was estimated as 24 kDa through SDS-PAGE, which showed only one band in silver staining. The purified enzyme showed an optimum temperature and pH of 50 °C and 9.0, respectively. Stability was well maintained, with high levels of activity at a pH of up to 11.0, including high stability at a temperature of up to 50 °C after 60 min of incubation. The inhibition test demonstrated strong inhibition by PMSF, a serine protease inhibitor, and Kinetic constants km and kcat for BAPNA were 0.517 mM and 5.0 S-1, respectively. The purified enzyme was also as active as casein, as analyzed by zymography. Therefore, we consider trypsin a promising enzyme for industrial processes, owing to its stability in a wide range of pH and temperature and activity even under immobilization.

Immobilization of Trypsin in Lignocellulosic Waste Material to Produce Peptides with Bioactive Potential from Whey Protein

In this study, trypsin (Enzyme Comission 3.4.21.4) was immobilized in a low cost, lignocellulosic support (corn cob powder—CCP) with the goal of obtaining peptides with bioactive potential from cheese whey. The pretreated support was activated with glyoxyl groups, glutaraldehyde and IDA-glyoxyl. The immobilization yields of the derivatives were higher than 83%, and the retention of catalytic activity was higher than 74%. The trypsin-glyoxyl-CCP derivative was thermally stable at 65 °C, a value that was 1090-fold higher than that obtained with the free enzyme. The trypsin-IDA-glyoxyl-CCP and trypsin-glutaraldehyde-CCP derivatives had thermal stabilities that were 883- and five-fold higher, respectively, then those obtained with the free enzyme. In the batch experiments, trypsin-IDA-glyoxyl-CCP retained 91% of its activity and had a degree of hydrolysis of 12.49%, while the values for trypsin-glyoxyl-CCP were 87% and 15.46%, respectively. The stabilized derivative trypsin-glyoxyl-CCP was also tested in an upflow packed-bed reactor. The hydrodynamic characterization of this reactor was a plug flow pattern, and the kinetics of this system provided a relative activity of 3.04 ± 0.01 U·g⁻¹ and an average degree of hydrolysis of 23%, which were suitable for the production of potentially bioactive peptides.

Trypsin from unicorn leatherjacket (Aluterus monoceros) pyloric caeca: purification and its use for preparation of fish protein hydrolysate with antioxidative activity

BACKGROUND

Fish proteases, especially trypsin, could be used to prepare fish protein hydrolysates with antioxidative activities. In this study, trypsin from the pyloric caeca of unicorn leatherjacket was purified by ammonium sulfate precipitation and soybean trypsin inhibitor (SBTI)-Sepharose 4B affinity chromatography. Hydrolysate from Indian mackerel protein isolate with different degrees of hydrolysis (20, 30 and 40% DH) was prepared using the purified trypsin, and antioxidative activities (1,1-diphenyl-2-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical-scavenging activities, ferric-reducing antioxidant power and ferrous-chelating activity) of the hydrolysate were determined.

RESULTS

Trypsin was purified 26.43-fold with a yield of 13.43%. The purified trypsin had a molecular weight (MW) of 23.5 kDa and optimal activity at pH 8.0 and 55 °C. It displayed high stability in the pH range of 6.0-11.0 and was thermally stable up to 50 °C. Both SBTI (0.05 mmol L(-1)) and N-p-tosyl-L-lysine-chloromethylketone (5 mmol L(-1)) completely inhibited trypsin activity. Antioxidative activities of the hydrolysate from Indian mackerel protein isolate increased with increasing DH up to 40% (P < 0.05). Based on sodium dodecyl sulfate polyacrylamide gel electrophoresis, the hydrolysate with 40% DH had a MW lower than 6.5 kDa.

CONCLUSION

The purified protease from unicorn leatherjacket pyloric caeca was identified as trypsin based on its ability to hydrolyze a specific synthetic substrate and the response to specific trypsin inhibitors. The purified trypsin could hydrolyze Indian mackerel protein isolate, and the resulting hydrolysate exhibited antioxidative activity depending on its DH.

Trypsin from the digestive system of carp Cirrhinus mrigala: purification, characterization and its potential application

Trypsin was purified 35.64-fold with 4.97% recovery from the viscera of carp Cirrhinus mrigala (mrigal) by ammonium sulfate precipitation, ion exchange and affinity chromatography. The purified enzyme was active at a wide range of pH (7.0-9.2) and temperature (10-50°C). The purified enzyme exhibited high thermal stability up to 50°C for 1h. The enzyme activity was stabilized by Ca(+2) (2mM) up to 7h at 40°C. The Km and kcat values of purified enzyme were 0.0672 mM and 92.09/s/mM, respectively. Soybean trypsin inhibitor and phenylmethylsulphonylflouride completely inhibited the enzyme activity. The specific inhibitor of trypsin, N-α-p-tosyl-L-lysine chloromethyl ketone inhibited 99.67% activity. Na(+), K(+) and Li(+) inhibited 20.99 ± 5.25%, 16.53 ± 4.80% and 18.99 ± 1.42% of enzyme activity, respectively. Divalent ions Mg(+2), Zn(+2), Co(+2), Hg(+2) and Cd(+2) inhibited 21.61 ± 2.22%, 31.62 ± 1.78%, 31.62 ± 1.96%, 85.68 ± 1.51% and 47.95 ± 2.13% enzyme activity, respectively. SDS-PAGE showed that the molecular mass of purified enzyme was 21.7 kDa. MALDI-TOF study showed a peptide sequence of AFCGGSLVNENKMHSAGHCYKSRIQV at the N-Terminal. This sequence recorded 76-84% identity with trypsin from Thunnus thynnus and other fish species. This confirmed that the purified protein was trypsin. The purified enzyme has potential applications in detergent and food industry because of its thermal stability and alkaline nature.

Metal-sensitive and thermostable trypsin from the crevalle jack (Caranx hippos) pyloric caeca: purification and characterization

BACKGROUND

Over the past decades, the economic development and world population growth has led to increased for food demand. Increasing the fish production is considered one of the alternatives to meet the increased food demand, but the processing of fish leads to by-products such as skin, bones and viscera, a source of environmental contamination. Fish viscera have been reported as an important source of digestive proteases with interesting characteristics for biotechnological processes. Thus, the aim of this study was to purify and to characterize a trypsin from the processing by-products of crevalle jack (Caranx hippos) fish.

RESULTS

A 27.5 kDa trypsin with N-terminal amino acid sequence IVGGFECTPHVFAYQ was easily purified from the pyloric caeca of the crevalle jack. Its physicochemical and kinetic properties were evaluated using N-α-benzoyl-DL-arginine-p-nitroanilide (BApNA) as substrate. In addition, the effects of various metal ions and specific protease inhibitors on trypsin activity were determined. Optimum pH and temperature were 8.0 and 50°C, respectively. After incubation at 50°C for 30 min the enzyme lost only 20% of its activity. Km, kcat, and kcat/Km values using BApNA as substrate were 0.689 mM, 6.9 s-1, and 10 s-1 mM-1, respectively. High inhibition of trypsin activity was observed after incubation with Cd2+, Al3+, Zn2+, Cu2+, Pb2+, and Hg2+ at 1 mM, revealing high sensitivity of the enzyme to metal ions.

CONCLUSIONS

Extraction of a thermostable trypsin from by-products of the fishery industry confirms the potential of these materials as an alternative source of these biomolecules. Furthermore, the results suggest that this trypsin-like enzyme presents interesting biotechnological properties for industrial applications.

Quantitative fate of chlorogenic acid during enzymatic browning of potato juice

The quantitative fate of chlorogenic acid (ChA) during enzymatic browning of potato juice was investigated. Potato juice was prepared in water without the use of any antibrowning agent (OX treatment). As a control, a potato juice was prepared in the presence of NaHSO(3) (S control). To study the composition of phenolic compounds in potato in their native states, also a potato extract was made with 50% (v/v) methanol containing 0.5% (v/v) acetic acid (MeOH control). Water-soluble low molecular weight fractions (LMWFs) and high molecular weight fractions (HMWFs) from S and OX extracts were obtained by ultrafiltration and dialysis, respectively. Pellets obtained after the OX treatment and the S and MeOH controls were also analyzed for ChA content. Whereas in the S-LMWF all ChA was converted to sulfonic acid adducts, no free ChA was found in the OX-LMWF, indicating its high reactivity upon enzymatic browning. Analysis of protein in the HMWFs showed a higher content of "reacted" ChA in OX (49.8 ± 7.1 mg ChA/100 g potato DW) than in S (14.4 ± 1.5 mg ChA/100 g potato DW), as evidenced by quinic acid release upon alkaline hydrolysis. The presence of quinic acid in S-HMWF was unexpected, but a mass balance incorporating the ChA content of LMWF, HMWF, and pellet for the three extractions suggested that ChA might have been attached to polymeric material, soluble in the aqueous environment of S but not in that of MeOH. Size exclusion chromatography, combined with proteolysis, revealed that ChA reacted with patatin and protease inhibitors to produce brown soluble complexes.