• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.3
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• pp.363-369
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• 2015

We investigated the effect of harvesting time on the proximate compositions and biological activities of Lactuca indica L. Seonhyang and wild species. The highest moisture content (91%) was obtained from Seonhyang harvested in June. The wild species harvested in August showed the highest crude protein (4.8%) and crude fiber contents (2.7%). Potassium contents were 626~684 mg/100 g, and no significant difference in harvesting time was observed between Seonhyang and wild species. Calcium and phosphate contents of Seonhyang leaves harvested in August were highest (350 mg/100 g and 123 mg/100 g, respectively). The highest total polyphenol and total flavonoid contents were observed for wild species harvested in June (60 mg/g and 126 mg/g, respectively). Ethanol extracts of Seonhyang and wild species leaves harvested in June showed the highest DPPH radical scavenging activity (95%). ${\alpha}$-Amylase inhibitory activity was highest (94.8%) in water extract of Seonhyang leaves harvested in July. Nitric oxide production inhibitory activity was $14.3{\mu}M$ in ethanol extracts of Seonhyang and $16.8{\mu}M$ in ethanol extracts of wild species harvested in June. Calcium content and ${\alpha}$-amylase inhibitory activity of Seonhyang leaves were greater than those of wild species leaves. These results suggest that Seonhyang leaf can be used to develop processed foods.

• Korean Journal of Food Science and Technology
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• v.25 no.6
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• pp.703-709
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• 1993

The changes in molecular size distribution of rice starch during extrusion cooking and simple heating of rice flour were compared and the effect of subsequent enzyme treatment on the molecular size was examined. A single-screw extruder was used with varing feed moisture contents ($17{\sim}29%$) and barrel temperatures ($100{\sim}150^{\circ}C$). An aluminium capsule immersed in oil bath ($100{\sim}200^{\circ}C$) was used for the simple heat treatment of rice flour. In case of extrusion cooking the mechanical energy input varied sharply at around 23% moisture content of the feed. At the feed moisture content of $17{\sim}23%$, a significant molecular size reduction of rice starch was observed by the gel permeation chromatography using Sephacryl S-1000 gel. The intact starch molecules of above $4{\times}10^{7}$ dalton were largely disintergrated by extrusion cooking of rice flour containing the moisture content less than 23%. It was mostly degraded further into the molecules having below $5{\times}10^{6}$ dalton by ${\alpha}-amylase$ treatment. But at the feed moisture content above 26% the starch did not show molecular size reduction either by extrusion cooking or by subsequent enzyme treatment. On the contrary little changes in molecular size of starch was occured by simple heating of rice flour containing the moisture less than 20%. but slight size reduction was observed at the moisture content above 23%, where the effect of ${\alpha}-amylase$ was also observed.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.2
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• pp.82-87
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• 2016

As contemporary society has become more complicated, specialized, and segmented, people are experiencing more diverse types of stress. In particular, while several factors associated with job stress have been examined among nurses, who belong to a professional group, the existing research has made no quantitative assessments of stress that reflect temporal differences in individuals. Therefore, the aim of this study is to understand the effects of job stress on alpha-amylase with regard to the working hours of nurses, to assess the variations in jobs stress over time, and provide basic data to improve the quality of nursing services. Ninety nurses working in three shifts in general, emergency, and intensive care wards of a university hospital in D City participated in this study. Salivary alpha-amylase (SAA) was extracted and analyzed at two-hour intervals from 07:00 to 15:00 from nurses on the day shift and from 23:00 to 07:00 from those working the night shift. The SAA level was highest between 23:00 and 01:00 for nurses in general wards ($mean{\pm}S.D.\;39.00{\pm}14.88$) and between 11:00 and 13:00 for those in both intensive care units and emergency wards ($mean{\pm}S.D.\;67.50{\pm}62.93$ and $mean{\pm}S.D.\;39.67{\pm}35.96$, respectively). The characteristic variation in SAA was significant between 23:00 and 01:00 (p < 0.01) and for those in their fifties or older (p < 0.01). The activation ratio of alpha-amylase, a stress reactant, showed an increase when the sympathetic nervous system was activated by mental stress; in addition, job stress was manifested with the effect of awakening at different time segments and at different ages among the nurses. With the aim of raising the level of service based on the nurses maintaining their mental health, it is necessary to focus sharply on the time segment for critical control and to conduct repetitive studies to determine the divisions of eustress critical values as well as to expand the population.

• Korean Journal of Food Science and Technology
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• v.16 no.4
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• pp.463-471
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• 1984

For the eventual alcohol production from uncooked starch, an efficient saccharification process was examined by using the combined action of steeping, pectin depolymerase, ${\alpha}-amylase$ and glucoamylase. The total sugar content of rice, sweet potato and tapioka used were 4.53, 4.26, and 3.92 mmole/g sample. $70\;{\pm}\;10%$ of the total sugar was hydrolyzed when cooked starch was saccharified under the condition which is currently used in industry. The smaller starch particle was used, the more saccharification was obtained. Efficient saccharification was obtained by treatment with 5% $H_2SO_4$ (sample: working volume = 1:2) at $60^{\circ}C$ for 12 hr. Optimization was carried out for the saccharification of uncooked starch by the combined action of pectin depolymerase, ${\alpha}-amylase$, and glucoamylase. The conditions are: pectin depolymerase; pH 4.5, $45^{\circ}C$, 2 hr, ${\alpha}-amylase$; pH 6.0, $60^{\circ}C$, 1 hr, and glucoamylase; pH 3.5, $60^{\circ}C$, 1 hr. Simultaneous treatment of the combined action of macerating, liquifying and saccharifying enzymes yielded better result than stepwise treatment of 3 enzymes. Degrees of saccharification of uncooked tapioka, rice and sweet potato were 82, 90.5, and 84.5%, respectively on the basis of total sugar, under the optimized conditions.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.7
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• pp.632-638
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• 2006

Characteristics of sweet (sugary, su) and super sweet (shrunken-2, sh2) corn seeds shelled by different threshing methods at different moisture content status were studied. Hybrid seeds of a su (Early Sunglow ${\times}$ Golden Cross Bantam 70, GCB 70) and a sh2 (Xtrasweet 82 ${\times}$Fortune) were dried to moisture content of 12, 15, 18, and 21%. Hand shelling did not give any mechanical damages to seeds, while an electrical corn thresher gave some visible mechanical damages. The emergence rate of hand shelled seeds was higher than that of machine shelled seeds by $6{\sim}14%$ for a su and by $9{\sim}18%$ for a sh2 hybrid depending on seed moisture contents in cold test. The optimum seed moisture content to reduce mechanical threshing damages and to improve seed quality was 15% for su and 12% for sh2 hybrid seeds. At the optimum seed moisture contents, germination rate at $25^{\circ}C$, emergence rate in the cold test and ${\alpha}-amylase$ activity were highest, while the percentage of damaged seeds and leakage of total sugars and electrolytes in soaking water were minimized.

• Korean Journal of Food Science and Technology
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• v.40 no.3
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• pp.251-256
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• 2008

Eoyukjang is a traditional sauce-type of Korean food that is similar to a soybean sauce made from fermented soybeans, and it is produced from a fermented mixture of sea foods, meats, and meju (soybean paste). This study examined periodical changes in the enzymatic activities of ${\alpha}$-amylase, esterase, ${\beta}$-glucosidase, protease, lipase, and lipoxygenase within the culture broth and solids of eoyukjang during 1 year of fermentation. The eoyukjang solids had 234-532% higher protein content than the culture broth. The specific activities of ${\alpha}$-amylase, esterase, ${\beta}$-glucosidase, and protease increased in both the culture broth and solids. Particularly, in the culture broth, ${\alpha}$-amylase, esterase, ${\beta}$-glucosidase, and protease activities rapidly increased (3- to 8-fold) until 10 months of fermentation, and then drastically decreased. However, the activities of lipase and lipoxygenase in both the culture broth and solids were less than 0.05 unit/mg of protein, respectively, throughout fermentation; thus, their activity levels were low and changed little over the 12 months. Overall, while the solids had higher protein content than the culture broth, the broth had greater enzyme activity levels during eoyukjang preparation.

• Microbiology and Biotechnology Letters
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• v.14 no.3
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• pp.213-218
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• 1986

Hybrid plasmid pEA24, shuttle vector YRp7 carrying amylase gene of Bacillus amyloliquefaciens, was transformed to yeast Saccharomyces cerevisiae, and the expression of B. amyloliquefaciens amylase gene in yeast was investigated. The frequency of transformation to S. cerevisiae DBY747 with YRp7 was increased by treatment of 40% polyethylene glycol (MW 4, 000), PH 7.0, at 3$0^{\circ}C$, and by regeneration used 2% top agar. The amount of cellular amylase activity produced by S. cerevisiae containing pEA24 was 2% of that secreted from B. amyloliquefaciens, but in case of S. cerevisiae transformant, the amylase secreted was not detected. A comparison of genetic stability of pEA24 and YRp7 plasmids in yeast was carried out by cultivation of transformants in tryptophan-supplement-medium. The pEA24 plasmid was more unstable than YRp7 in S. cerevisiae. The size of pEA24 extracted from S. cerevisiae transformants was found to be identical with that from E. coli transformants by agarose gel electrophoresis.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2001.06a
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• pp.73-76
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• 2001

$\alpha$-Glucosidase contributing $\alpha$-glucan metabolism in microorganisms is characterized by the variety in substrate recognition. Recent studies on microbial enzymes show that $\alpha$-glucosidases are divided into two groups, family I and family n, in which family I enzymes have four conserved catalytic-regions of $\alpha$-amylase family. The presentation focusing on the difference of the $\alpha$-glucosidase families reviews i) the catalytic amino-acid residues of nucleophile and acid/base catalyst, and ii) the molecular evolution of two families.

• Journal of Microbiology and Biotechnology
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• v.17 no.8
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• pp.1242-1248
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• 2007

Genomic analysis of a hyperthermophilic archaeon, Thermococcus onnurineus NA1 [1], revealed the presence of an open reading frame consisting of 1,377 bp similar to ${\alpha}$-amylases from Thermococcales, encoding a 458-residue polypeptide containing a putative 25-residue signal peptide. The mature form of the ${\alpha}$-amylase was cloned and the recombinant enzyme was characterized. The optimum activity of the enzyme occurred at $80^{\circ}C$ and pH 5.5. The enzyme showed a liquefying activity, hydrolyzing maltooligosaccharides, amylopectin, and starch to produce mainly maltose (G2) to maltoheptaose (G7), but not pullulan and cyclodextrin. Surprisingly, the enzyme was not highly thermostable, with half-life ($t_{1/2}$) values of 10 min at $90^{\circ}C$, despite the high similarity to ${\alpha}$-amylases from Pyrococcus. Factors affecting the thermostability were considered to enhance the thermo stability. The presence of $Ca^{2+}$ seemed to be critical, significantly changing $t_{1/2}$ at $90^{\circ}C$ to 153 min by the addition of 0.5 mM $Ca^{2+}$. On the other hand, the thermostability was not enhanced by the addition of $Zn^{2+}$ or other divalent metals, irrespective of the concentration. The mutagenetic study showed that the recovery of zinc-binding residues (His175 and Cys189) enhanced the thermo stability, indicating that the residues involved in metal binding is very critical for the thermostability.

• Journal of Microbiology and Biotechnology
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• v.18 no.9
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• pp.1555-1563
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• 2008

A novel $\alpha$-amylase ($\alpha$-1,4-$\alpha$-D-glucan glucanohydrolase, E.C. 3.2.1.1), ScAmy43, was found in the culture medium of the phytopathogenic fungus Sclerotinia sclerotiorum grown on oats flour. Purified to homogeneity, ScAmy43 appeared as a 43 kDa monomeric enzyme, as estimated by SDS-PAGE and Superdex 75 gel filtration. The MALDI peptide mass fingerprint of ScAmy43 tryptic digest as well as internal sequence analyses indicate that the enzyme has an original primary structure when compared with other fungal a-amylases. However, the sequence of the 12 N-terminal residues is homologous with those of Aspergillus awamori and Aspergillus kawachii amylases, suggesting that the new enzyme belongs to the same GH13 glycosyl hydrolase family. Assayed with soluble starch as substrate, this enzyme displayed optimal activity at pH 4 and $55^{\circ}C$ with an apparent $K_m$ value of 1.66 mg/ml and $V_{max}$ of 0.1${\mu}mol$glucose $min^{-1}$ $ml^{-1}$. ScAmy43 activity was strongly inhibited by $Cu^{2+}$, $Mn^{2+}$, and $Ba^{2+}$, moderately by $Fe^{2+}$, and was only weakly affected by $Ca^{2+}$ addition. However, since EDTA and EGTA did not inhibit ScAmy43 activity, this enzyme is probably not a metalloprotein. DTT and $\beta$-mercaptoethanol strongly increased the enzyme activity. Starting with soluble starch as substrate, the end products were mainly maltotriose, suggesting for this enzyme an endo action.