• Korean Journal of Microbiology
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• v.6 no.2
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• pp.41-53
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• 1968

Studies on the carbohydrate metabolism of yeast as influenced by gamma-irradiation from cobalt-60 have been carried, then the mechanisms of radiation effect on respiration and fermentation were discussed under considerations of permeable changes of irradiated cell membrane. The cells of baker's yeast (Saccharomyces cerevisiae) which had been gamma-irradiated of 240 k.r. doses for an hour, then were put into aerobic oxidation and anaerobic fermentation without substrate. Total and fractionated carbohydrates of irradiated yeast cells were determined by calorimetric method with anthrone and orcinol reagents, the amounts of total carbohydrate, trehalose, RNA-ribose, PCA-soluble glycogen, alkali-soluble glycogen, acetic acid-soluble glycogen, mannan and glucan were determined according to the course of aerobic oxidation and anaerobic fermentation. It is found that the carbohydrates of irradiated cells leak out and amount of the losses teaches eleven times more than that of control, the volume of losses are seems to be replaced by water, it can be suggested the damage of gamma-irradiation occurs in the site of passive transport of cell membrane. The endogeneous aerobic respiration of irradiated cells are increased much more than control, the synthesis of reserve glycogen, glucan and RNA-ribose promoted much more than control. The anaerobic fermentation of irradiated cells are also increased than that of control, but the breakdown of carbohydrate is less than endogeneous respiration of irradiated cells. The synthetic rate is also less than that of aerobic oxidation. In irradiated yeast cells, trehalose is revealed to be primary substrate for endogeneous carbohydrate metabolism, so it is proved that the enzymic patterns are not changed but the activities of enzymes relating endogeneous respiration and autofermentation is activated. It is to be considerable to distiguish endogeneous respiration and autofermentation from exogeneous respiration and fermentation on irradiation, for membrane permeability changes and loses out carbohydrate by ionizing radiation.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.4
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• pp.277-282
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• 2002

This paper proposes a nonlinear adaptive controller based on back-stepping method for tracking reference substrate concentration by manipulating dilution rate in a continuous baker's yeast cultivating process in stirred tank bioreactor. Control law is obtained from Lyapunov control function to ensure asymptotical stability of the system. The Haldane model for the specific growth rate depending on only substrate concentration is used in this paper. Due to the uncertainty of specific growth rate, it has been modified as a function including the unknown parameter with known bounded values. The substrate concentration in the bioreactor and feed line are measured. The deviation from the reference is observed when the external disturbance such as the change of the feed is introduced to the system. The effectiveness of the proposed controller is shown through simulation results in continuous system.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.3
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• pp.284-288
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• 2005

Baker's yeast was disrupted in a 1.4-L stainless steel horizontal bead mill under a continuous recycle mode using 0.3 mm diameter zirconia beads as abrasive. A single pass in continuous mode bead mill operation liberates half of the maximally released protein. The maximum total protein release can only be achieved after passaging the cells 5 times through the disruption chamber. The degree of cell disruption was increased with the increase in feeding rate, but the total protein release was highest at the middle range of feeding rate (45 L/h). The total protein release was increased with an increase in biomass concentration from 10 to $50\%$(w/v). However, higher heat dissipation as a result of high viscosity of concentrated biomass led to the denaturation of labile protein such as glucose 6-phosphate dehydrogenase (G6PDH). As a result the highest specific activity of G6PDH was achieved at biomass concentration of $20\%$(ww/v). Generally, the degree of cell disruption and total protein released were increased with an increase in impeller tip speed, but the specific activity of G6PDH was decreased substantially at higher impeller tip speed (14 m/s). Both the degree of cell disruption and total protein release increased, as the bead loading increased from 75 to $85\% (v/v)$. Hence, in order to obtain a higher yield of labile protein such as G6PDH, the yeast cell should not be disrupted at biomass concentration and impeller tip speed higher than $20\%(w/v)$ and 10 m/s, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.5
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• pp.542-544
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• 2002

This study was carried out to evaluate the ciliates Euplotes sp. as a live food for marine fish larvae. The ciliates and the rotifers Brachionus plicatilis, which were cultured with the baker's yeast Saccharomyces cerevisiae and the $\omega$-yeast emulsified with cuttle fish liver oil, were supplied to the larvae of flounder Paralichthys olivaceus and grouper Epinephelus akaara. Considering the size difference between the ciliates 68 $\cdot$ 7 $\mu$n and the rotifers 160 $\cdot$ 20 $\mu$n, the rotifers and ciliates were supplied to the larvae tank with the density of 2 inds./mL and 20 inds./mL, respectively. The survival rate and growth in length of the flounder larvae fed on rotifer were significantly higher than those on Euplotes sp.. In grouper larvae which have a small mouth diameter, even the survival rate of the larvae fed on the ciliates was better than that on the rotifers, it was very low less than $20\%$. Therefore, Euplotes sp. seem to be incongruent as a live food for marine fish larvae.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.74.3-74
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• 2001

This paper proposes a nonlinear adaptive controller based on back-stepping method for tracking reference substrate concentration by manipulating dilution rate in a continuous baker´s yeast cultivating process in stirred tank bioreactor. Control law is obtained from Lyapunov control function to ensure asymptotical stability of the system. The Haldane model for the specific growth rate depending on only substrate concentration is used in this paper. Due to the uncertainty of specific growth rate, it has been modified as a function including the unknown parameter with known bounded values. The substrate concentration in the bioreactor and feed line are measured. The deviation from the reference is observed when the external disturbance such as the change of the feed is introduced to the system ...

• Applied Biological Chemistry
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• v.37 no.5
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• pp.402-408
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• 1994

For the examination of the role of monocerin(1) on the biological activity, (8S, 9S, 11R)-(-)-monocerin(20) and (9S, 11R)-(+)-fusarentin 4, 5-dimethyl ether(19) were synthesized by a condensation of the benzylic anion of ethyl 2, 3, 4-trimethoxy-6-methylbenzoate(16) with modifyed (R)-ethyl 3-hydroxyhexanoate (9). In a key step, bioreduction with active dried baker's yeast in organic solvent system was employed to get a chiral aldehyde 12. Their phytotoxic activities were tested on rice seedlings and lettuce seeds.

• Journal of Aquaculture
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• v.6 no.3
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• pp.147-157
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• 1993

The harpacticoid copepod, Tigriopus japonicus is one of the most important zooplankton as a live food for the production of marine fish fry. Thus, the salinity tolerance and the optimum culture environment of this copepod in terms of salinity, temperature and light were examined. The food values of 6 kinds of phytoplankters and 2 kinds of yeast were also investigated for mass culture of this copepod. The results are as follows: After 5 day culture in the experiment of salinity tolerance, the survival rates of the gravid female at $0\%\;and\;90%o\;were\;40\%\;and\;70\%$, respectively. However, at salinity ranging from $2\%o\;to\;80\%o$, high survival rates above $85\%$ were observed. It means T. japonicus is very euryhalinous species. Temperature was more important factor than salinity for the fecundity of T. japonicus. The optimum culture conditions of this species were $24^{\circ}C,\;24\%o$, and 3,000 lux with 24 L: 0D. Under these culture conditions, the average fecundity from a gravid female per spawning was 38 nauplii, and the interval time between spawnings were 2.05 days. Phaeodactylum tircornutum seemed to be the most suitable phytoplankton as a live food for T. japonicus, and the large chlorophyta, Tetraselmis suecica showed the lowest food value among 6 phytoplankters and 2 yeasts. The food value of w-yeast was better than that of baker's yeast, and it is similar to that of phytoplankton such as Amphora sp., Chlorella ellipsoidea and Nannochloris oculata. So, the w-yeast seems to be appropriate food source for mass culture of T. japonicus.

• Journal of the East Asian Society of Dietary Life
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• v.23 no.5
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• pp.546-560
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• 2013

In this study, a natural fermentation starter formulation was developed for manufacturing Korean bread products by substituting baker's yeast with naturally fermented blueberry starters. As the incubation time of the blueberry extracts increased, the pH and total titratable acidity increased. The sweetness (brix%) of blueberry extracts containing various amounts of sugar were higher than the other sample. The result of alcoholicity for naturally fermented blueberry extracts, the fermented blueberry extract containing 20% sugar was highest. Lactic acid bacteria counts increased until the 4th day; however, it decreased from the 5th day, and viable yeast counts increased consistently until the 5th day. The volume for naturally fermented blueberry extracts increased as the incubation time increased. As the fermentation time of blueberry starters increased, the pH of bread dough decreased. The RVA analysis conveyed that wheat flour retrogradation was retarded by increasing the blueberry starter content. The weight of pan breads containing blueberry starters were higher than that of the control, while the volume, specific volume and baking loss rate were lower than those of the control. The moisture content of pan breads containing blueberry starter decreased as storage time increased. In analyzing the visible mold colony during 7 days of storage at $28^{\circ}C$, mold growth in pan breads containing the blueberry starter was retarded. The hardness of breads containing blueberry starters were significantly increased as storage time increased. The breads containing 50% naturally fermented blueberry starter have acceptable sensory properties. In conclusion, these results indicated that 50% of natural fermentation blueberry starter could be very useful as a substitute for yeast when making naturally fermented bread.

• Korean Journal of Food Science and Technology
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• v.37 no.2
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• pp.199-205
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• 2005

Physicochemical quality characteristics of seed mashes were investigated for development of new creative breadmaking in bakery. Aridity of seed mashes fermented with Koji, lactic acid bacteria, and baker's yeast was slightly lower than those fermented with Koji and yeast. ${\alpha}-Amylase$, saccharifying amylase, and acidic protease activities of seed mash composed of water (560 mL) and Koji (400 g) were 0.26 SKB, 36 SP, and 645 HUT/g, respectively. Reducing sugar content of seed mash made with Koji increased up to 13.04% after 36 hr fermentation, then decreased drastically thereafter, whereas that of seed mashes made with Koji, yeast, and lactic acid bacteria increased up to 6.5% at 6 hr, decreased to 1 to 2.5% at 12 hr, and remained less than 0.7% after 18 hr fermentation. Total organic acid contents were 10.4-12.25mg/mL. Flavor compounds including ethyl acetate, ethyl caprylate, isoamyl acetate, and p-vinyl guaiacol were detected in seed mash fermented with Koji, yeast, and L. brevis. These results show use of seed mash fermented with Koji, S. cerevisiae, and lactic acid bacteria enhances bread flavor.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.8
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• pp.1245-1252
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• 2003

A starter formulation was developed to substitute a baker's yeast with natural starter when manufacturing bread products. To develop an active starlet, starter was formulated varying with types of wheat flours, level of water contents and various nutrients. Activities of starter were investigated in terms of viable counts of microbes and change of pH and total titratible acidity Domestic wheat flours contain 100 times more number of lactic acid bacteria than yeast regardless of types of wheat flours. The more protein contents in wheat flours, the more stable microbes in starter. This was considered to be the result of buffering effect of wheat proteins. The optimum level of protein content to ensure the activity of starter was more than 12.0%. Optimum level of water content in active starter was 110% based on strong flour. The more water or the less water had the tendency of decreasing viable counts of microbes. Addition of salt and sucrose had increased the activity of starters. However oligosaccharides did not affect the activity of starter. The optimum concentrations of salt and sucrose were 1.0% and 5.0% respectively. Bread with the starter was higher scored than breads with yeast in terms of all the quality and sensory characteristics except their volumes. In conclusion, a starter formulated with strong flour 100%, water 110%, salt 1% and sucrose 5% was considered to have high potential as a substitute of yeast in making natural bread.