• Journal of Life Science
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• v.25 no.6
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• pp.631-637
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• 2015

Streptavidin, a protein produced by Streptomyces avidinii, strongly binds up to four molecules of vitamin H, d-biotin exhibiting the dissociation constant of about 10⁻¹⁵ M. This strong binding affinity has been applied for detection and characterization of numerous biological molecules suggesting expression and purification of functional streptavidin should be very useful for the application of this streptavidin-biotin interaction. To express a soluble streptavidin in Escherichia coli, We synthesized streptavidin genes and cloned into pET-22b plasmid, which uses T7 RNA polymerase/T7 promoter expression systems containing pelB leader for secretion into periplasmic space and six polyhistidine tags at C-terminus for purification of expressed proteins. Although streptavidin is toxic to Escherichia coli due to strong biotin binding property, streptavidin was expressed very sufficiently in a range of 10-20 mg/ml. In SDS-PAGE, the size of purified protein was shown as 17 kDa in denatured condition (boiling) and 68 kDa in native condition (without boiling) suggesting tetramerization of monomeric subunit by non-covalent association. Further analysis by size-exclusion chromatography supported streptavidin’s tetrameric structure as well. In addition, soluble streptavidin detected biotinylated proteins in westernblot indicating its functional activity to biotin. Taken these results together, it concluded that our simple expression system was able to show high yield, homotetrameric formation and biotin binding activity analogous to natural streptavidin.

• Microbiology and Biotechnology Letters
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• v.26 no.3
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• pp.244-249
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• 1998

An extracellular polysaccharide, methylan, was produced under the specific conditions by Methylobacterium organophilum from methanol. The specific growth rate of cells was approximately constant regardless of C/N ratio and the specific product yield was maximum at a C/N ratio of 30. Methylan production was suppressed by the deficiency of mineral ions such as Mn$^{++}$ or Fe$^{++}$ ion. The optimal pH for cell growth and methylan production was 7. Whereas the optimal temperature for cell growth was found to be 37$^{\circ}C$, that for methylan production was 3$0^{\circ}C$. The methanol concentration above 4% completely inhibited the cell growth. The initial methanol concentration for the maximal production of methylan was 0.5% (v/v) and above this concentration, methylan production was markedly inhibited. To overcome the substrate toxicity and inhibition for both cell growth and methylan production, a fed-bach culture of intermittent feeding within 5 g/l methanol was conducted under the optimal culture condition. Methylan production of was stimulated by nitrogen limitation and methylan was accumulated up to 8.7 g/1 and cell mass also increased up to 12.4 g/l.

• Microbiology and Biotechnology Letters
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• v.42 no.3
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• pp.258-266
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• 2014

Sweet potato soju (SPS), a form of traditional distilled alcoholic liquor in Korea, is manufactured by the distillation of fermented broth under normal pressure, thus providing it for a uniquely smooth taste infused with the flavor of sweet potato. After distillation, the lees of SPS is produced as by-product and discarded. In this study, the ethanol and hot water extracts of lees of SPS, and their subsequent organic solvent fractions using hexane, ethylacetate (EA), butanol, and water residue were prepared in an effort at the efficient re-use of the lees of SPS. The ethanol extraction yield was 1.36-fold higher than that of the hot water extraction, and the EA fraction revealed the highest total polyphenol content among the solvent fractions. The various extracts and solvent fractions did not demonstrate hemolytic activity at up to 0.5 mg/ml concentrations against human red blood cells. In the bioactivity assay, only the EA fraction displayed a broad spectrum of anti-microbial activity against different pathogenic and food spoilage bacteria, and demonstrated significant anti-coagulation activity by inhibitions of thrombin, prothrombin and blood coagulation factors. Furthermore, only the EA fraction from the hot water extract of the lees of SPS showed anti-platelet aggregation activity, which is comparable to aspirin (a commercially available drug). Our results suggest that the EA fraction of the hot water extract prepared from the lees of SPS has a high potential as a novel resource for anti-microbial and anti-thrombosis agents.

• Korean Journal of Food Science and Technology
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• v.28 no.2
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• pp.267-272
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• 1996

Effect of freezing of soybeans on instrumental and sensory textures of soybean curd was investigated. The hardness, gumminess and chewiness of soybean curd prepared with frozen soybeans were about three times as high as those prepared with unfrozen soybeans, while cohesiveness and elasticity were affected little by freezing. Sensory evaluation showed that freezing improved the quality of soybean curd. Instrumental and sensory textures of soybean curd prepared with frozen soybeans were excellent and almost same regardless of the boiling time when the soy slurry was boiled for 2.5 min or 5 min. However, the textures of soybean curd prepared with unfrozen soybeans were deteriorated by reducing the boiling time to 2.5 min. It was postulated that freezing facilitate the heat-denaturation of soyprotein to enhance aggregation of soy proteins and formation of cross-linkage between aggregate and $Ca^{++}$. Frozen soybeans resulted in soybean curd which lower fat content, while protein content of soybean curd was almost he same. Frozen soybeans gave a lower yield of soybean curd, which is supposed to be caused by the more fat loss during whey-off.

• Korean Journal of Food Science and Technology
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• v.29 no.3
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• pp.516-521
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• 1997

Effect of amylose content on the physical properties of resistant starches (RS) from autoclaved maize starches (with starch:water=1:3.5, at $121^{\circ}C$) which were repeated up to 4 times heating-cooling cycles, were investigated by water uptake, scanning electron microscope (SEM) and differential scanning calorimetry (DSC). Amylose content of waxy maize starch (Amioca), common maize starch (PFP), high amylose starch(Amaizo, Amylomaize VII) were 0%, 29%, 50%, and 72%, respectively. Yield of RS increased as amylose content increased. Water uptake of all kinds of native starch was higher than that of RS, but lower than that of autoclaved starch. By SEM, RS showed some small particles on surface but the size of particles was different with amylose content. Single endothermic transition peak exhibited at $40{\sim}70^{\circ}C$ in autoclaved Amioca and PFP (crystalline melting of amylopectin) and at $132{\sim}169^{\circ}C$ in autoclaved Amaizo and Amylomaize VII(crystalline melting of amylose) by DSC. RS from all kinds of autoclaved starches except Amioca showed single endothermic peak over $155^{\circ}C$ but the enthalpy was not related to amylose content.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.2
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• pp.209-215
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• 2007

The functional sauce from shrimp byproducts (heads, shells and tails) was prepared and examined for its characterization. The results of volatile basic nitrogen (VBN) suggested that shrimp byproducts were suitable materials for preparing functional sauce. The shrimp hydrolysate, which was incubated with Alcalase for 30 min, showed excellent yield and ACE inhibitory activity. The concentrated sauce from shrimp byproduct was high in crude protein, while low in VBN content and salinity when compared to commercial shrimp sauce. The total amino acid content (23,095.2 mg/100 mL) of concentrated sauce from shrimp byproduct was higher than that (4,582.5 mg/100 smL) of commercial shrimp sauce; also, the major amino acids were glutamic acid, aspartic acid, arginine and lysine. The free amino acid content and taste value of concentrated sauce from shrimp byproduct were 2,705.5 mg/100 mL and 81.0, respectively. The results on the taste value of concentrated sauce from shrimp byproducts suggested that the major taste active compounds among free amino acids were glutamic acid and aspartic acid.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.1
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• pp.72-75
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• 2008

Quality properties of red ginseng prepared with different cultivation years of fresh ginseng produced in Punggi region were investigated. Fresh ginseng cultivated for 4, 5, or 6 years was steamed for 3.5 hr and dried for 24 hr at $60{\sim}65^{\circ}C$ and subsequently for $3{\sim}4$ days at $40^{\circ}C$ under commercial conditions. Compared to 6 years-old roots, the five years-old roots showed similar or some lower quality properties in terms of color, appearance, diameter, and inside quality, but higher ones in length and yield of prepared red ginseng. In particular, the levels of ginsenoside $Rg_3$ and $Rh_2$, which are known as specific components in red ginseng, were the highest in 5 years-old roots. The result shows that fresh ginseng of 5 years-old roots produced in Punggi region can be utilized as a raw material for the manufacture of high-quality red ginseng.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.8
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• pp.1239-1244
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• 2003

Microcapsules were prepared by coacervation method using acetone/liquid paraffin system to control the ripening of kimchi. Eudragit E100, which was soluble at below pH 5.0 in aqueous solution, was used to make microcapsules to be sensitive to acidity of kimchi. The microcapsules with Eudragit E100 containing grapefruit seed extract (GFSE) showed the highest yield of 92.13%, the size of microcapsules was decreasing as increasing the amount of aluminium stearate, a dispersing agent. Morphology of the microcapsules determined by scanning electron microscopy showed spherical forms. GFSE, encapsulated antimicrobial agents, was quickly released at acidic buffer (pH 4,5,6) within 1 storage day. However, 70% of encapsulated GFSE in Eudragit E100 microcapsules was continuously released at pH 7 till 3 days, and it was sustained till 9 days. Characteristics of kimchi containing microcapsules of GFSE were analysed with ripening period. Decease of pH in kimchi was retarded with the added GFSE microcapsules till 2 days of fermentation, but GFSE did not affect pH in kimchi after 3 days. Total numbers of microorganisms and lactic acid microorganisms in kimchi were decreased with increasing the amount of the added GFSE microcapsules, however, the effect of controlled released GFSE from pH sensitive Eudragit E100 microcapsules was hard to detect. These results suggest the possibility of pH sensitive microcapsules for high qualify of kimchi.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.8
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• pp.1038-1044
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• 2006

The effects of the addition of soybeans cultured by mycelia of Pleurotus eryngii (SMP) on the characteristics of tofu were studied. Protein and ash contents of SMP were higher than those of untreated soybeans: 43.23 and 6.34% for treated soybeans, respectively, and 40.42 and 5.90% for untreated soybeans. But lipid and carbohydrate contents of SMP were lower. For minor elements, Mg and Ca contents of SMP were higher and P was lower than control. Tofu could be manufactured when SMP was added below 25% to the untreated soybean. In scanning electron microscopic observation, tofu tended to break down as the ratio of SMP was over 25% to the untreated soybean. The addition of SMP $(5{\sim}15%)$ increased the yield of tofu to $1.5{\sim}3.5%$. In textural characteristics, hardness of tofu increased as the ratio of SMP increased up to 20%. Cohesiveness, chewiness, springiness and gumminess were high in tofu which was made with $5{\sim}15%$ SMP. Savory taste and overall acceptability of the tofu prepared with $5{\sim}15%$ SMP were higher than those of control when evaluated by sensory test.

• Journal of the Korean Society of Food Science and Nutrition
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• v.13 no.2
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• pp.149-155
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• 1984

Raw and cooked pig's head, feet and tails were evaluated for yield, proximate composition, caloric value, and the contents of amino acids, minerals and vitamins. The yields of the raw pig's head, feet and tails were 67.4%, 46.1% and 67.6%, respectively. Corresponding values for the cooked were 54.1%, 34.3% and 47.6% respectively. No significant differences were observed for proximate composition between these samples and any other source3 of the meats. The high energy values, 253.8-310.5 Cal/100 g, of the samples were largely due to the fat content. Among the essential amino acids, these products showed a higher lysine, leucine and threonine content, and lower methionine and tryptophan content. The total amounts of non-essential amino acids were more than half of those of all amino acids. Neither the raw nor the cooked pig's head, feet and tails contained vitamin A. On these data, pig's head, feet and tails tissue have a relatively low in vitamin B content as compared to conventional pork cuts.