The effect of salt, pH, and temperature stress on the cellular level of antioxidant enzymes, catalase and superoxide dismutase (SOD) and glycerol-3-phosphate dehydrogenase (G3PDH) was studied in Debaryomyces nepalensis NCYC 3413, a halotolerant yeast. The catalase activity increased in different phases, while SOD and G3PDH activities declined in late stationary phase. A significant increase in SOD activity was observed under different stress as compared to control. Salt and temperature stress enhanced the catalase activity where as it was suppressed by pH stress. G3PDH level increased with salt stress, however, no significant change was observed under pH and temperature stress. The observations recorded in this investigation suggested that D. nepalensis has an efficient protective mechanism of antioxidant enzymes and G3PDH against salt, pH, and temperature stresses. © 2010 Springer Science+Business Media, LLC.

Sathyanarayana Naidu Gummadi

Department Of Biotechnology

Sawan Kumar

catalase

GLYCEROL 3 PHOSPHATE DEHYDROGENASE

superoxide dismutase

article

cell metabolism

controlled study

DEBARYOMYCES

DEBARYOMYCES NEPALENSIS

ENVIRONMENTAL STRESS

enzyme activity

fungal strain

fungus growth

FUNGUS ISOLATION

nonhuman

osmolarity

priority journal

Salinity

signal transduction

temperature stress

GLYCEROLPHOSPHATE DEHYDROGENASE

Hydrogen-Ion Concentration

Saccharomycetales

Salts

Stress, Physiological

Temperature

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Current Microbiology

Debaryomyces nepalensis NCYC 3413, a food spoiling yeast isolated from rotten apple, has been previously demonstrated as halotolerant yeast. In the present study, we assessed its growth, change in cell size, and measured the intracellular polyol and cations (Na(+) or K(+)) accumulated during growth in the absence and presence of different concentrations of salts (NaCl and KCl). Cells could tolerate 2 M NaCl and KCl in defined medium. Scanning electron microscopic results showed linear decrease in mean cell diameter with increase in medium salinity. Cells accumulated high amounts of K(+) during growth at high concentrations of KCl. However, it accumulated low amounts of Na(+) and high amounts of K(+) when grown in the presence of NaCl. Cells grown in the absence of salt showed rapid influx of Na(+)/K(+) on incubation with high salt. On incubation with 2 M KCl, cells grown at 2 M NaCl showed an immediate efflux of Na(+) and rapid uptake of K(+) and vice versa. To withstand the salt stress, osmotic adjustment of intracellular cation was accompanied by intracellular accumulation of polyol (glycerol, arabitol, and sorbitol). Based on our result, we hypothesize that there exists a balanced efflux and synthesis of osmolytes when D. nepalensis was exposed to hypoosmotic and hyperosmotic stress conditions, respectively. Our findings suggest that D. nepalensis is an Na(+) excluder yeast and it has an efficient transport system for sodium extrusion.

Extremophiles : life under extreme conditions

Osmotic adaptation in halotolerant yeast, Debaryomyces nepalensis NCYC 3413: role of osmolytes and cation transport.

The effect of temperature and salts on the growth of halotolerant yeast, Debaryomyces nepalensis was studied by growing cells in shake flask on rotary shaker and cell growth was measured. Specific growth rate (μ) of D. nepalensis increased with increase in temperature from 15 to 35°C and then decreased with increase in temperature beyond 35°C when grown in presence and absence of different salts. At 40°C, both NaCl and KCl at 1.0 M concentration enhanced the specific growth rate. D. nepalensis showed synergistic effect on thermal and salt stress when grown at 35-40°C (0.5 M NaCl) and 30-40°C (0.5 and 1.0 M KCl). The organism was able to revert its specific growth rate when temperature was shifted from 20°C to its optimum temperature for growth (30°C) only in the presence of salts, which was not observed in the absence of salts. However, the same phenomenon was not observed when the temperature was shifted from 40 to 30°C. Decrease in activation energy was observed for growth at salt concentration beyond 0.5 M of NaCl and KCl. © 2008 Academic Journals Inc.

Fulltext

American Journal of Food Technology

Effects of temperature and salts on growth of halotolerant Debaryomyces nepalensis NCYC 3413

Debaryomyces nepalensis, a halotolerant food-spoiling yeast could grow in complex (YEPD) medium at different pHs ranging between 3.0 and 11.0 in the absence of salt and at pH 3.0-9.0 in the presence of different concentrations of NaCl and KCl. The specific growth rate of D. nepalensis was not affected by the initial pH of the medium in the absence of salts, whereas it was affected in the presence of salts. At 2 M NaCl and KCl, the organism exhibited a synergistic effect on pH and salt stress, which was unique in the Debaryomyces species. Irrespective of the initial pH and salt, the intracellular pH of D. nepalensis was ~7.0. Significant organic acid was produced at neutral and alkaline pH and organic acid production increased with the increase in pH and salt. Very specific organic acids are produced in the presence of NaCl and KCl. Our observation would contribute to a better understanding of the physiological phenomenon of halotolerance in D. nepalensis. © 2008 Springer Science+Business Media, LLC.

Growth of halotolerant food spoiling yeast Debaryomyces nepalensis NCYC 3413 under the influence of pH and salt

In this study, Debaryomyces nepalensis NCYC 3413 isolated from rotten apple was studied for its halotolerance and its growth was compared with that of Saccharomyces cerevisiae in high salt medium. The specific growth rate of D. nepalensis was not affected by KCl even up to a concentration of 1 M, whereas NaCl and LiCl affected the growth of D. nepalensis. Among all tested salts, LiCl showed maximum inhibition on growth. At all conditions, halotolerance of D. nepalensis was much higher than that of S. cerevisiae. D. nepalensis showed maximum viability (80-100%) when grown in KCl, which was higher than with NaCl and LiCl. Pectinase production by D. nepalensis was noted at all high salt concentrations, namely, 2 M NaCl, 2 M KCl, and 0.5 M LiCl, and the maximum specific activity was observed when the strain was grown in 2 M NaCl. © 2007 Springer Science+Business Media, LLC.

Effect of salts on growth and pectinase production by halotolerant yeast, Debaryomyces nepalensis NCYC 3413

Extremophiles

Temperature downshift induces antioxidant response in fungi isolated from Antarctica

Differential response of the catalase, superoxide dismutase and glycerol-3-phosphate dehydrogenase to different environmental stresses in Debaryomyces nepalensis NCYC 3413

Journal	Current Microbiology
ISSN	03438651
Open Access	No