• 한국미생물·생명공학회지
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• 제28권6호
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• pp.349-354
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• 2000

Culture conditions and nitrogen sources were optimized for production of erythritol, a natural sweetener, by Candida magnoliae M26. The optimal culture conditions were found to be culture temperature of $28^{\circ}C$, initial pH of 7, aeration of 1 vvm and agitation speed of 500 rpm in a 2.5 1 jar-fermentor. Glucose was chosen as the best carbon cource bsed on cell growth and erythritol productivity. Kight steep water(LSW) and corn steep liquor (CSL) which are by-products in starch processing from corn were tested as a nitrogen source substitute for yeast extract. The use of either LSW or CSL did not change the fermentation performance. The experimental results using LSW and CSL showed 1.5 times higher in cell growth and almost the same value in erythritol productivity com-pared with the control fermentation using yeast extract as a nitrogen source. These results suggested that either LSW of CSL could be used as a nitrogen source in a large-scale fermentation for erythritol production.

• Journal of Microbiology and Biotechnology
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• 제18권9호
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• pp.1522-1528
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• 2008

The morphogenetic behavior of a tropical marine Yarrowia lipolytica strain on hydrophobic substrates was studied. Media containing coconut oil or palm kernel oil (rich in lauric and myristic acids) prepared in distilled water or seawater at a neutral pH supported 95% of the cells to undergo a transition from the yeast form to the mycelium form. With potassium laurate, 51 % of the cells were in the mycelium form, whereas with myristate, 32% were in the mycelium form. However, combinations of these two fatty acids in proportions that are present in coconut oil or palm kernel oil enhanced the mycelium formation to 65%. The culture also produced extracellular lipases during the morphogenetic change. The yeast cells were found to attach to the large droplets of the hydrophobic substrates during the transition, while the mycelia were associated with the aqueous phase. The alkane-grown yeast partitioned more efficiently in the hydrophobic phases when compared with the coconut oil-grown mycelia. A fatty acid analysis of the mycelial form revealed the presence of lauric acid in addition to the long-chain saturated and unsaturated fatty acids observed in the yeast form. The mycelia underwent a rapid transition to the yeast form with n-dodecane, a medium-chain aliphatic hydrocarbon. Thus, the fungus displayed a differential behavior towards the two types of saturated hydrophobic substrates.

• Journal of Microbiology and Biotechnology
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• 제4권3호
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• pp.215-221
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• 1994

Two strains of yeast (RA-74-2 and RA-912) showing superior fermenting ability at a high temperature were isolated from soils and wastewaters by an enrichment culture method. Based on the morphological and physiological charateristics, the two strains were identified as Saccharomyces cerevisiae and Kluyveromyces marxianus, respectively. RA-74-2 was able to grow upto $43^{\circ}C$ and sustain similar fermenting ability in the temperatures range from 30 to $40^{\circ}C$. In addition, the sugar- and ethanol-tolerance of RA-74-2 were 30% (w/v) glucose and 10% (v/v) ethanol, which appeared to be higher than those of nine other industrial yeast strains currently being used in the alcohol factories. The thermotolerant ethanol fermenting yeast RA-912 showed identical growth in the temperatures range from 35 to $45^{\circ}C$ and was resistant to various heavy metals. The quality and quantity of byproducts of the isolated yeast strains in fermentation broth after fermentation at $40^{\circ}C$ and $45^{\circ}C$ were similiar with those obtained at $30^{\circ}C$. These results show that RA-74-2 can be adopted for the ethanol fermentation process where the expenses for cooling system is significant, and suggest that RA-912 may be applied in either SSF(simultaneous saccharification and fermentation) or Flash-fermentation process and RA-912 may be used as a gene donor for the development of thermotolerant ethanol-fermenting yeasts.

• Journal of Microbiology and Biotechnology
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• 제17권5호
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• pp.847-852
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• 2007

This study investigated an efficient method for the extraction of astaxanthin from the red yeast Xanthophyllomyces dendrorhous. The extraction process comprised three steps: 1) cultivating the yeast; 2) treating the yeast culture suspension with microwaves to destroy the cell walls and microbodies; and 3) drying the yeast and extracting the astaxanthin pigment using ethanol, methanol, acetone, or a mixture of the three as the extraction solvent. Ultimately, various treatment tests were performed to determine the conditions for optimal pigment extraction, and the total carotenoid and astaxanthin contents were quantified. A frequency of 2,450 MHz, an output of 500 watts, and irradiation time of 60 s were the most optimum conditions for yeast cell wall destruction. Furthermore, optimal pigment extraction occurred when using a cell density of 10g/l at $30^{\circ}C$ over 24 h, with a 10% volume of ethanol.

• Food Science and Biotechnology
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• 제17권4호
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• pp.739-744
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• 2008

The method of yeast propagation has an influence on yeast physiology, fermentation ability, flocculation rate, and taste stability of beer. In order to find optimal conditions for propagation, several parameters were investigated in combinations. The bottom brewing yeast grown at $10^{\circ}C$ indicated that a higher flocculation capacity during the $1^{st}$ fermentation. However, the taste stability and the aroma profile were not affected by parameters of propagation investigated. The beer quality was rather affected by storage duration. In addition, a correlation between tasting and chemiluminescence was found at the beer, which was produced using bottom brewing yeast. The propagation at $10-25^{\circ}C$ with addition of zinc ion indicated the best condition to improve fermentation ability, flocculation rate, and filterability for bottom brewing yeast, whereas the propagation at $30^{\circ}C$ with addition of zinc ion showed the best condition to increase fermentation ability for top brewing yeasts.

• Journal of Microbiology
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• 제44권6호
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• pp.617-621
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• 2006

Coprinellus congregatus secreted a laccase isozyme when the culture was transferred to an acidic liquid medium (pH 4.1). The laccase cDNA gene (clac2) was used as a probe for cloning of the genomic laccase gene (lac2) including the promoter (Plac2). The open reading frame (ORF) of lac2 had 526 deduced amino acids and four conserved copper binding domains as other fungal laccases. Recombinant plasmid (pRSlac2p-cDNA) of lac2 cDNA with its own promoter was transformed in Saccharomyces cerevisiae. Expression of the transformed lac2 gene was induced by oxidative stress ($H_2O_2$) in yeast and the survival rate of the transformed yeast strain was greatly increased when compared with that of the control strain transformed with pRS316 yeast vector.

• 동아시아식생활학회지
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• 제10권4호
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• pp.288-297
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• 2000

To understand the effect of radish on growth of food born microorganisms, mashedflesh radishes were extracted by using acetone and distilled water. Their effect was assayed by measuring the optical density of cultural broth of food born microorganisms. In the experiment, seven strains of yeast were used as the test organism. Acetone extract inhibited growth of the cells of L. plantarum, L. sake and Danmuji film yeast. Growth of the film yeast was drastically inhibited in the concomitant presence of 0.03% extract, while other microbes such as L. faecalis, P. pentosaceus, B/ subtilis and E. coli grew by succeeding cultivation for 4 to 8 hour after addition of the extract. Water extract, on contrast to acetone extract, at he concentrations of 0.1∼1.5% stimulated the growth of lactic acid bacteria. Culture of L. faecalis and L. sake showed an optical density higher than that of control by 40∼50 times. The effect was not so apparent against E. coli, S. aureus and Danmuji film yeast.

• Journal of Microbiology and Biotechnology
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• 제2권2호
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• pp.108-114
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• 1992

The fermentative characteristics in ethanol production from lactose, with increased ethanol tolerance, of a fusant yeast strain constructed by protoplast fusion of Saccharomyces cerevisiae and Kluyveromyces fragilis were studied. The ethanol tolerance of this strain was increased to 8.0%, compared with the parent K. fragilis. During batch ethanol fermentation the optimal cultivation conditions for this fusant yeast were an initial pH of 4.5, a culture temperature $30^\circ{C}$. stirring at 100 rpm without aeration in 10% lactose medium (supplied with 1.0% yeast extract). Using this fusant strain in whey fermentation to ethanol, maximum ethanol production reached 3.41% (w/v) (theoretical yield; 66.7%) after a 48 hour cultivation period.

• Biotechnology and Bioprocess Engineering:BBE
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• 제3권2호
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• pp.115-118
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• 1998

Utilization of yeast extract and formation of byproduct metabolite were investigated for hyperthermophilic archaeon Sulfolobus solfataricus (DSH 1617). In both batch and fed-batch cultivations of S. solfataricus, maximal cell density, {{{{ { NH}`_{4 } ^{ +} }}} ion production and pH change were highly dependent on the ratio of yeast extract to glucose in the medium. Variation of {{{{ { NH}`_{4 } ^{ +} }}}} ion level was identified as a major cause of pH change during cultivation, and acidification of culture broth was attributed to consumption of {{{{ { NH}`_{4 } ^{ +} }}}} ions rather than formation of acid byproducts. It was also observed that increase of {{{{ { NH}`_{4 } ^{ +} }}}} ion concentrations in the medium resulted in greater degree of growth inhibition.

• Journal of Microbiology and Biotechnology
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• 제8권3호
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• pp.291-294
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• 1998

Transfer of Candida albicans grown in Sabouraud medium to the RPMI medium induces the transition from a nonpathogenic yeast form to a pathogenic hyphal form. This transition was severely inhibited in a dose-dependent manner when deer antler extract was added to the RPMI medium in a nontoxic range (up to $500{\mu}g$). In that range, deer antler extract inhibited the hyphal transition and cell growth, whereas no effect was observed on the yeast growth. When hydrophobic or hydrophilic fractions were prepared by detergent-solubilization of deer antler extract, the hydrophobic fraction showed a large degree of inhibition of the hyphal growth in Candida albicans. Neither fraction affected the growth in the yeast form. The pattern of chitin localization in the culture of the yeast form grown in RPMI in the presence of deer antler extract was confirmed by calcofluor staining and this exhibited strongly the suppression of hyphal transition.