• KSBB Journal
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• v.15 no.6
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• pp.566-572
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• 2000

Experimental studies were carried out to develop an osmotolerant mutant of Candida magnoliae JH and to determine the optimum concentrations of carbon and nitrogen sources to improve erythritol yield and productivity. Mutants of C. magnoliae JH were prepared by treatment with ethylmethane sulfonate, and osmotolerant mutants were isolated from the agar plate colonies containing 2.5 M KCI. Among the mutants isolated, one mutant M26 was finally selected based on erythritol yield and productivity. In shake flask culture, glucose proved to be the best carbon source and the optimum yeast extract concentration was 5 g/L based on 100 g/L glucose. The erythritol yield and productivity of mutant M26 were greater than wild type in 100 g/L glucose medium. in the fermentation experiments, erythritol production increased with increased glucose concentration, up to a limit of 250 g/L. The maximum concentration of erythritol achieved 127.5 g/L, and the yield and productivity of erythritol production were 51.0% and 0.63 g/L-h, respectively.

• Journal of Microbiology and Biotechnology
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• v.9 no.1
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• pp.84-90
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• 1999

The growth of Bifidobacterium breve strain HP2 was completely inhibited by the addition of lactate higher than 4.0％ but not by the addition of acetate. Two kinds of lactate-tolerant mutants were isolated by the nitrosoguanidine treatment, enrichment on a liquid medium with 5％ lactate, and selection on agar plates with 5％ lactate. The mutants were not only able to grow in the presence of 5％ lactate but also improved in viable cell stability in the acidic pH range. In a pH-controlled fermentor, mutant N-1-5 grew at a rate slower than that of the wild type but its growth yield was higher. Notably, mutants were more halotolerant and more osmotolerant than the wild type and they were able to grow in the presence of 3％ NaCl or 25％ lactose at which the wild type entirely stopped the growth. The enzyme activities involved in the lactose metabolism in B. breve were measured to elucidate the biochemical basis for lactate tolerance. In the mutants, activities of several enzymes including phosphoglucomutase decreased compared to the wild-type, which may explain their lower growth rate. However, the activity of lactate dehydrogenase or its nature of inhibition by lactate was not altered.

• Korean Journal of Food Science and Technology
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• v.36 no.3
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• pp.456-460
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• 2004

Effects of sigma factor (${\sigma}^{B}$) on biofilm formation in Listeria monocytogenes 10403S and ${\sigma}^{B}-deficient$ sigB null mutant were studied under high osmotic and low temperature conditions. In brain heart infusion (BHI) medium containing 6% NaCl, wild type 10403S and ${\sigma}^{B}-deficient$sigB null mutant formed biofilms of $6.83{\pm}0.38\;and\;5.33{\pm}0.45\;log\;cfu/cm^{2}$, respectively. L. monocytogenes 10403S in BHI medium containing 6% NaCl formed 4.7 times larger biofilm than without NaCl. Culture of L. monocytogenes 10403S and sigB null mutant at $4^{\circ}C$ did not show any significant differences in biofilm formation. The results suggest biofilm formation is activated by ${\sigma}^{B}$ and NaCl, whereas not affected by low temperature stress in L. monocytogenes 10403S. More studies are necessary to determine biofilm formation mechanism in osmotolerant L. monocytogenes.