• Journal of Microbiology and Biotechnology
• /
• v.14 no.6
• /
• pp.1142-1149
• /
• 2004

Streptococcus mutans has the capacity of inducing dental caries. Thus, to develop a novel way of preventing dental caries, a cell wall hydrolase-producing strain was isolated and its characteristics were investigated. Among 200 alkalophilic strains isolated from soil, 8 strains exhibited lytic activities against Streptococcus mutans. However, strain YU5215 with the highest cell wall hydrolase activity was selected for further study. Strain YU5215 was identified as a novel strain of Bacillus based on analyzing its 16S rDNA sequence and Bergey's Manual of Systematic Bacteriology, and thus designated as Bacillus mutanolyticus YU5215. The optimal conditions for the production of the cell wall hydrolase from Bacillus mutanolyticus YU5215 consisted of glucose ($0.8\%$), yeast extract ($1.2\%$), polypeptone ($0.5\%$), $K_{2}HPO_{4}\;(0.1\%$), $MgSO_{4}{\cdot}7H_{2}O$ ($0.02\%$), and $Na_{2}CO_{3}\;(1.0\%$) at pH 10.0. Bacillus mutanolyticus YU5215 was cultured at 30^{circ}C for 72 h to produce the cell wall hydrolase, which was then purified by acetone precipitation and CM-agarose column chromatography. The molecular weight of the lytic enzyme was determined as 22,700 Da by SDS-PAGE. When the cell wall peptidoglycan of Streptococcus mutans was digested with the lytic enzyme, no increase in the reducing sugars was observed, while the free amino acids increased, indicating that the lytic enzyme had an endopeptidase-like property. The amino terminus of the cell wall peptidoglycan digested by the lytic enzyme was determined as a glutamic acid, while the lytic site of the lytic enzyme in the Streptococcus mutans peptidoglycan was identified as the peptide linkage of L-Ala and D-Glu.

• 한국생물공학회:학술대회논문집
• /
• 2000.11a
• /
• pp.191-193
• /
• 2000

A whole-cell biocatalyst was constructed by immobilizing an enzyme on the surface of the yeast Saccharomyces cerevisiae. The gene encoding Bacillus macerans cyclodextrin glucanotransferase(CGTase) was fused with the AGA2 gene encoding a small peptide disulfide-linked to the aga1, a cell wall protein of a-agglutinin. The plasmid was introduced S. cerevisiae and expressed in the medium consisting of 10g/L yeast extract, 20g/L peptone, and 20g/L galactose. The activity was detected with the formation of cyclodextrin(CD) from 10g/L soluble starch. Surface display of CGTase was also verified with the halo-test, flow cytometry, and immunofluorescence microscopy. The recombinant S. cerevisiae produced ${\alpha}-cyclodextrin$ more efficiently than the free CGTase by simultaneous fermentation and cyclization as yeast consumes glucose and maltose which are inhibitors for CD synthesis.

• Korean Journal of Microbiology
• /
• v.24 no.3
• /
• pp.295-301
• /
• 1986

The bacteria, which were capable of producing ${\beta}-1$, 3-glucanase inducibly by utilizing cell wall of Aspergillus fumigatus as a sole carbon source, were isolated from soil in the campus of Kyungpook National University. Among them, the strain which produced the enzyme excellently was selected and identified to be Pseudomonas stutzeri KF 13 by morphological, cultural and physiological examination. The optimal conditions for the enzyme production from Pseudomonas stutzeri KF 13 were investigated. the enzyme production was reached maximum state shen the broth cultured for 72hr at $30^{\circ}C$. And the enzyme showed the highest activity in the medium containing 3.5% cell wall as an inducer, 15% yeast autolysate as a nitrogen source and 0.05% $MnSO_4$ at pH 7.5.

• Korean Journal of Microbiology
• /
• v.29 no.6
• /
• pp.397-401
• /
• 1991

Yeast-form cells of cadmium ion-tolerant Hansenula anomala B-7 were changed to mycelial cells in medium containing more than $400\mu$g/ml of cadmium. Moreover, the mycelial cells were exchanged into clumped cells in a medium containing more than $1,000\mu$g/ml of cadmium. Optimal conditions of mycelial cell formation were achieved in the presence of .$1,000\mu$g/ml of cadmium with shaking cultivation for 7 days. Glucan and mannan contents of the yeast cell wall frown with $1,000\mu$g/ml of cadmium decreased by 10% compared with those grown without cadmium. However, protein and lipid contents increased about 20% respectively. By cadmium, no significant findings in specific amino acid contents were discovered.

• Korean Journal of Food Science and Technology
• /
• v.9 no.2
• /
• pp.97-105
• /
• 1977

1) In order to obtain a microbial strain having a strong yeast cell wall lytic activity, about 156 isolates capable of forming clear zones on baker's yeast-peptone-bouillon agar plate were obtained from soil, mud and water samples and a strain K-42 with the highest lytic activity was identified as Bacillus circulans. 2) Effect of carbon sources on the lytic enzyme production by the K-42 strain was in the decreasing order of maltose>glucan>xylose>control in 2-day culture and of lactose>galactose>glucan>control in 3-day culture. Effect of inorganic nitrogen sources was in the decreasing order of ammonium acetate>sodium nitrate>control in 2-day culture and of ammonium chloride>ammonium oxalate>control in 3-day culture, whereas organic nitrogen sources except milk casein showed an increase in 2-day culture and a decrease in 3-day culture. Synergistic effect of carbon sources and nitrogen sources was not observed. 3) The enzyme production by the K-42 strain was greatly affected by pH change of the culture medium, thus a high lytic activity could be maintained by keeping the pH range of $7{\sim}8$ and adding carbon or nitrogen sources. 4) Optimum conditions for the lytic activity of the K-42 strain were obtained at $pH\;7{\sim}8$ and $60^{\circ}C$ and the extent of hydrolysis toward heated yeast cell wall was 65%.

• Korean Journal of Poultry Science
• /
• v.32 no.1
• /
• pp.49-54
• /
• 2005

An experiment was conducted to investigate whether dietary yeast (Saccharomyces cerevisiae, SC) and its' structural components, i.e., yeast cell-extract (YE) and yeast cell-wall (CW) could influence growth performance, ileal morphology and serum lipids of male broiler chickens. There were four dietary treatments, each consisting of 6 replicates (10 birds per replicate). Chickens were fed a corn-soybean meal base control diet and diets containing SC ($0.5\%$), YE ($0.25\%$) and CW ($0.25\%$), respectively for 5-wk-experimental period. Dietary SC, YE and CW versus the control diet did not affect growth performance of male broiler chickens. Ileal morphology as to villus height, crypt depth and villus:crypt ratio of birds fed on the control diet was not significant from those fed on diets rich in SC, YE and CW, respectively. Dietary SC significantly lowered (P<0.05) serum total cholesterol by on average $19.7\%$ as compared to the control group. In addition, chickens fed on diets with either YE or CW lowered serum cholesterol by on average 15.3 and $12.5\%$, respectively as compared to the control albeit that the former only reached statistical significance. In conclusion, our study observed the hypocholesterolemic effect of SC in male broiler chickens. Moreover, YE, i.e., an extract of intracellular components of SC contains active molecules that are responsible far lowering serum cholesterol concentrations, but their identification at the molecular level needs to be assessed.

• 한국생물공학회:학술대회논문집
• /
• 2003.10a
• /
• pp.301-301
• /
• 2003

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.27 no.6
• /
• pp.1077-1085
• /
• 1998

The effects of yeast on the fermentation of kimchi were investigated. The treatments were divided into two groups; yeast treatment during salting of Chinese cabbage(YS) and yeast treatment added in kimchi preparation(YF kimchi). The edible periods of the kimchi after yeast treatment during salting (YS kimchi) was extended 4~5 days by the results of pH, acidity, sensory quality. The activities of amylase, polygalacturonase and galactosidase of YS kimchi were retained at low levels compared to non treated condition throughout all fermentation periods, whereas protease activity was not significant different from the non treated condition. In addition, the contents of total hexose and uronic acid did not show remarkable change throughout fermentation, but total pentose was decreased by more than 7% at the early middle stage of fermentation(7~14 day after soaking). The change of free amino acid content was decreased by 16~44% than the non treated condition. In contrast, in the YF kimchi, the sensory quality was not good. The activities of amylase, protease, polygalacturonase and gal actosidase were appreciably higher than that of the non treated condition. Meanwhile, the contents of total hexose, total pentose and uronic acid, as products of degradation of cell wall constituents by the above enzymes, were decreased by 18~68% throughout fermentation than the non treated con dition, and total free amino acids were higher than the YS kimchi. Thus, yeast treatment during salting was found to be more effective to extend the edible periods of the kimchi.

• Journal of Aquaculture
• /
• v.22 no.1
• /
• pp.68-73
• /
• 2009

Yeast has been widely used as a food organism for mass culture of rotifer and also considered as a partial substitute food for microalga in shellfish culture. But the dietary value of yeast is poorer than that of microalga due to its low nutrition and thick cell wall. This study was carried out to find a nutritious yeast species as a food organism and to investigate the nutritional value of manipulated yeast for shellfish. First of all, three species of yeast (Saccharomyces cerevisiae, Candida utilis, Kluyveromyces fragilis) and their manipulated yeast were tested on the survival (%) and growth of Artemia nauplii and Mytilus edulis larvae, which were representative filter feeding animal and easy to control. The survival (%) and growth of Artemia nauplii fed C. utilis were higher than those fed S. cerevisiae or K. fragilis. The growth of Artemia nauplii and M. edulis larvae, which were fed manipulated yeast was higher than that fed non-manipulated one. The manipulated yeast with higher removal rate of cell wall showed better dietary value for Artemia nauplii and M. edulis larvae. M. edulis larvae fed mixed-diet with Isochrysis galbana (50%) and manipulated C. utilis (50%) showed significantly higher growth than those fed single-diet with I. galbana. It means that manipulated C. utilis can substitute I. galbana at least 50% for M. edulis larvae.

• Journal of Microbiology and Biotechnology
• /
• v.1 no.3
• /
• pp.212-219
• /
• 1991

Four species of yeast, Saccharomyces cerevisiae, Candida utilis, Saccharomycopsis flbuligera, and Schwanniomyces castellii were evaluated for their ability to bioconvert potato processing waste water into microbial protein and the resulting single-cell proteins were evaluated as protein sources for rainbow trout, using in vitro analyses. The studies indicated that Schwanniomyces castellii, which utilizes starch dircetly and converts it into cell mass efficiently, was suitable for the bioconversion. In the single-stage continuous bioconversion, the yield S. castellii cell mass, which contained approximately 37% protein, was 77%, at dilution rate 0.25 $h^{-1}$. Reduction of total carbohydrate was 81%. During batch fermentations, cell mass yield was about 72% and total carbohydrate reduction was 81%. Among the yeasts tested, S. castellii possessed the most fragile cell wall and had a favorable amino acid profile for salmonid fish; protein score of 86% (Met). In an in vitro pepsin digestibility test 80% digestibility (23~38% above control) was observed when cells were pre-heated in a steam bath for 30 min. Results presented should be regarded as being preliminary in nature because they were derived from single experiments.