• Applied Biological Chemistry
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• v.35 no.5
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• pp.339-345
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• 1992

In order to enhance the processing quality and utility of alaska-pollack meat, the optimum conditions for the preparation of pronase hydrolysate and the synthesis of plastein were investigated. The optimum temperature and pH for the hydrolysis of alaska-pollack by pronase were $40^{\circ}C$ and pH 7.0. The reaction time and enzyme concentration were 4 hr and 1,000 units per g of substrate. Under the above optimum conditions alaska-pollack was hydrolyzed by pronase yielding a hydrolytic degree of about 89%. Pronase hydrolysate was employed as substrate for plastein synthesis. The 30% pronase hydrolysates were adjusted to pH 7 for fruit-bromelain and pH 5 for stem-bromelain, and then plastein were synthesized by 1% bromelain at $40^{\circ}C$ for 24 hr. The plasteins synthesized by fruit- and stem-bromelain were consisted of peptides having average peptide length of 22.6 and 20.8 under the optimum synthetic conditions. The plastein synthesis reaction reduced considerably the bitterness of pronase hydrolysate.

• Food Science of Animal Resources
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• v.30 no.3
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• pp.443-448
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• 2010

Casein phosphopeptide (CPP) enhances calcium absorption in humans. Lactic acid bacteria (LAB) are capable of synthesis of cell-surface proteinase, which can hydrolyze milk protein and release several types of peptides in the medium. This study was conducted to characterize proteinase of LAB and to evaluate the CPP production from bovine milk. The content of CPP of milk produced by cell-free extract of LAB was determined based on the quantity of decomposed peptide from casein using the O-phthaldialdehyde (OPA) method. The proteolytic activity of LAB was assayed using fluorescein isothiocyanate (FITC)-labeled casein. Casein appeared to be a better substrate than whey proteins for extracellular proteinases of LAB. During fermentation, milk proteins were hydrolyzed by extracellular proteinase of LAB, resulting in an increase in the amount of free $NH_3$ groups. Overall, the results presented here indicate that CPP produced by LAB may be a promising material for novel applications in the dairy industry.

• Molecules and Cells
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• v.44 no.7
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• pp.517-528
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• 2021

A recent genetic study with Brucella abortus revealed the secretion activator gene A (SagA) as an autolysin component creating pores in the peptidoglycan (PGN) layer for the type IV secretion system (T4SS) and peptidoglycan hydrolase inhibitor A (PhiA) as an inhibitor of SagA. In this study, we determined the crystal structures of both SagA and PhiA. Notably, the SagA structure contained a PGN fragment in a space between the N- and C-terminal domains, showing the substrate-dependent hinge motion of the domains. The purified SagA fully hydrolyzed the meso-diaminopimelic acid (DAP)-type PGN, showing a higher activity than hen egg-white lysozyme. The PhiA protein exhibiting tetrameric assembly failed to inhibit SagA activity in our experiments. Our findings provide implications for the molecular basis of the SagA-PhiA system of B. abortus. The development of inhibitors of SagA would further contribute to controlling brucellosis by attenuating the function of T4SS, the major virulence factor of Brucella.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.3
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• pp.197-204
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• 2021

In MBR, extracellular polymeric substance (EPS) is known as an important factor of fouling; soluble EPS (sEPS) affects internal contamination of membrane, and bound EPS (bEPS) affects the formation of the cake layer. The production of EPS changes according to the composition of influent, which affects fouling characteristics. Therefore, in this study, the effects of the F/M ratio on the sEPS concentration, bEPS content, and fouling were evaluated. The effects of F/M ratio on the amount and composition of EPS were confirmed by setting conditions that were very low or higher than the general F/M ratio of MBR, and the fouling occurrence characteristics were evaluated by filtration resistance distribution. As a result, it was found that the sEPS increased significantly with the increase of the F/M ratio. When the substrate was depleted, bEPS content decreased because bEPS was hydrolyzed into BAP and seemed to be used as a substrate. In contrast, when the substrate is sufficient, UAP (utilization-associated products) was rapidly generated in proportion with the consumption of the substrate. UAP has a relatively higher Protein/Carbohydrate ratio (P/C ratio) than BAP, and this means, it has a higher adhesive force to the membrane surface. As a result, UAP seems like causing fouling rather than BAP (biomass-associated products). Therefore, R_f (Resistance of internal contamination) increased rapidly with the increase of UAP, and R_c (Resistance of cake layer) increased with the accumulation of bEPS in proportion, and as a result, the fouling interval was shortened. According to this study, a high F/M ratio leads to an increment in UAP generation and accumulation of bEPS, and by these UAP and bEPS, membrane fouling is promoted.

• Food Science of Animal Resources
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• v.41 no.4
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• pp.608-622
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• 2021

Bioactive peptides have great potentials as nutraceutical and pharmaceutical agents that can improve human health. The objectives of this research were to produce functional peptides from ovotransferrin, a major egg white protein, using single enzyme treatments, and to analyze the properties of the hydrolysates produced. Lyophilized ovotransferrin was dissolved in distilled water at 20 mg/mL, treated with protease, elastase, papain, trypsin, or α-chymotrypsin at 1% (w/v) level of substrate, and incubated for 0-24 h at the optimal temperature of each enzyme (protease 55℃, papain 37℃, elastase 25℃, trypsin 37℃, α-chymotrypsin 37℃). The hydrolysates were tested for antioxidant, metal-chelating, and antimicrobial activities. Protease, papain, trypsin, and α-chymotrypsin hydrolyzed ovotransferrin relatively well after 3 h of incubation, but it took 24 h with elastase to reach a similar degree of hydrolysis. The hydrolysates obtained after 3 h of incubation with protease, papain, trypsin, α-chymotrypsin, and after 24 h with elastase were selected as the best products to analyze their functional properties. None of the hydrolysates exhibited antioxidant properties in the oil emulsion nor antimicrobial property at 20 mg/mL concentration. However, ovotransferrin with α-chymotrypsin and with elastase had higher Fe³⁺-chelating activities (1.06±0.88%, 1.25±0.24%) than the native ovotransferrin (0.46±0.60%). Overall, the results indicated that the single-enzyme treatments of ovotransferrin were not effective to produce peptides with antioxidant, antimicrobial, or Fe³⁺-chelating activity. Further research on the effects of enzyme combinations may be needed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.4
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• pp.370-377
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• 2001

Flounder brain cytosol contains protein inhibitors that markedly inhibit the activity of partially purified brain membrane phospholipase D (PLD) which is dependent on phosphatidylinositol 4,5-bisphosphate ($PIP_2$) but insensitive to ADP-ribosylation factor (ARF), The PLD inhibitors have been enriched through several chromatographic steps and characterized with respect to size and mechanism of inhibition. Sequential chromatography of the brain cytosol yielded six inhibitor fractions, Two (IIA and IIB) of six inhibitor fractions showed the $PIP_2$-phosphatase activities. IIA was identified as synaptojanin, a nerve terminal protein that has known to be a member of the inositolpolyphosphate 5-phosphatase family, by immunoblot analysis. IIB showed an apparent molecular mass of 158 kDa by Superose 12 gel filtration chromatography and was immunologically distinct from synaptojanin. IIB hydrolyzed $PIP_2$, yielding only phosphatidylinositol phosphate (PIP) as product, suggesting that IIB hydrolyzes only one phosphate from either the 4- or 5-position of PI (4,5)$P_2$. These studies demonstrate that the existence of multiple $PIP_2$-phosphatases have been implicated in the negative regulation of $PIP_2$-dependent PLD activity within flounder brain.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.6
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• pp.875-881
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• 1998

To develop functional food material with angiotensin converting enzyme (ACE) inhibitory peptides, muscle protein of anchovy, Engraulis japonica was hydrolyzed during 48 hrs by digestive pretenses such as pepsin, trypsin, $\alpha$-chymotrypsin, and commercial proteases such as papain, bromelain, complex enzyme, Elavourzyme, Novozym, Neutrase, Protamex and Alcalase. The only $50\%$ ethanol soluble hydrolysates were tested for inhibitory activity against ACE and yield of $50\%$ ethanol soluble peptide-nitrogen ($ESPN_{50}$). ACE inhibition effects and yield of $ESPN_{50}$ occurred as hydrolysis time increased to 8 hrs, Among those pretenses tested, hydrolysates by Alcalase and $\alpha$-chymohypsin had greater ACE inhibitory activity (80 and $74\%$, reipectively) with eletated levels of $ESPN_{50}$ (48 and 58 mg/ml, respectively), while Protamex hydrolysates had greater ACE inhibitory activities ($73\%$) with reduced levels of $ESPN_{50}$ (7.2mg/ml) than others. Amino acid compositions of $50\%$ ethanol solubles obtained from those hydrolysates were rich in glutamic acid, aspartic acid, cysteine and leucine.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.19 no.1
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• pp.20-26
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• 1986

Very little information is available in the literature on storage of fish sauce. Therefore, microbiological and chemical chracteristics during storage and quality of fish sauce were investigated and discussed to present data about the optimum storage condition. The chopped sardine meat was mixed with equal amount of water and $9\%$(w/w) of $75\%$ vital wheat gluten and then hydrolyzed by addition of commercial proteolytic enzymes such as bromelain, papaya protease, ficin and a enzyme mixture (Pacific Chem. Co.) for 4 hours at $52.5^{\circ}C$. The reaction mixture was heated for 30 min at $100^{\circ}C$ for enzyme inactivation, pasteurization and color development and then centrifuged for 20 min at 4,000 rpm. Table salt and benzoic acid were added for bacteriostatic effect and stored for 80 days at $15{\pm}1^{\circ}C$ and $30{\pm}1^{\circ}C$. The results were summarized as follows: 1. The amount of amino-nitrogen and pH of fish sauce were almost unchanged during storage. 2. Mininum concentration of salt for bacteriostatic activity was $9\%$(w/w) regardless of addition of benzoic acid. 3. the yields of amino-nitrogen were $63.1\%$ for the hydrolysate prepared without enzyme, $79.7\%$ for that with bromelain, $69.9\%$ with ficin, $74.3\%$ with papaya pretense, and $78.1\%$ with enzyme mixture, respectively. 4. The contents of amino-nitrogen were $4510.0mg\%$ on the dry basis for the product prepared by autolysis, $5483.2mg\%$ for that prepared with bromelain, $5305.7mg\%$ with ficin, $4994.1mg\%$ with papaya protease and $5582.3mg\%$ with the enzyme mixture, respectively. 5. The contents of crude protein were $51.35\%$ on the dry basis for the product prepared by autolysis and 55 to $59\%$ for prepared with commercial enzymes. 6. The hydrolysate prepared with the enzyme mixture revealed a little stronger meaty taste than any other products. 7. The level of crude protein in residues was still high ($69.5{\sim}77.2\%$ on the dry basis) and might be originated from the added vital wheat gluten.

• Korean Journal of Food Science and Technology
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• v.46 no.2
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• pp.165-172
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• 2014

Mixed fermentation of cow milk was performed by sequential co-cultures with Bacillus subtilis and Lactococcus lactis. After a first fermentation step with B. subtilis for 6 h, the number of viable cells increased to $2.5{\times}10^8$ CFU/mL. The second fermentation step with L. lactis resulted in increased viable cells $1.09{\times}10^{10}$ CFU/mL for 3 days and increased acidity. However, the number of viable B. subtilis cells was decreased greatly to $5{\times}10^1$ CFU/mL following fermentation with L. lactis. Milk proteins were markedly hydrolyzed by the first fermentation after 2 h, and the second fermentation induced curd formation in milk. However, after 4 h, the first fermentation resulted in higher whey separation and 80 mg% tyrosine content. Gamma-aminobutyric acid (GABA) production was dependent upon the degree of protein hydrolysis by first fermentation. Second fermentation resulted in 0.14% GABA. The milk fermented by B. subtilis indicated the rough surface of yogurt depended upon the degree of protein hydrolysis. In conclusion, set-type yogurt was efficiently produced by co-culturing of milk, and fortifying with peptides, GABA, and probiotics.

• Journal of Life Science
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• v.17 no.1 s.81
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• pp.132-136
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• 2007

When alginate lyase gene (aly) from Pseudoalteromonas elyakovii was expressed in E. coli, most of the gene product was produced as aggregated insoluble particles known as inclusion bodies. In order to produce a soluble and active form of alginate lyase, E. coli cells fore cotransformed with the plasmids designed to permit coexpression of aly together with molecular chaperones such as DnaK/DnaJ/GrpE or GroEL/ES chaperones. The results revealed that the coexpression of aly together with DnaK/DnaJ/GrpE chaperone had a marked effect on the production of this protein as a soluble and active form, presumably through facilitating correct folding of alginate lyase protein. The optimal concentration of L-arabinose for the induction of DnaK/DnaJ/GrpE chaperone was found to be 0.05 mg/ml. When DnaK/DnaJ/GrpE chaperone was coexpressed, about 34% in the total alginate lyase was produced in the soluble fraction. By addition of 10% cetylpyridinium chloride, a clear zone around the colony coexpressing aly and DnaK/DnaJ/GrpE chaperone was formed, indicating that the alginate in the medium was hydrolyzed by active alginate lyase enzyme.