Effects of potassium sorbate on growth patterns, morphology, and heat resistance of Zygosaccharomyces rouxii at reduced water activity

1992 ◽  
Vol 38 (12) ◽  
pp. 1252-1259 ◽  
Author(s):  
David A. Golden ◽  
Larry R. Beuchat
Keyword(s):  
Heat Resistance ◽  
Water Activity ◽  
Growth Patterns ◽  
Potassium Sorbate ◽  
Heat Sensitivity ◽  
Growth Morphology ◽  
Zygosaccharomyces Rouxii ◽  
Inhibition Of Growth ◽  
Reduced Water ◽  
Sorbate Concentration

A study was made of the effects of potassium sorbate on growth, morphology, and heat sensitivity of an osmotolerant yeast, Zygosaccharomyces rouxii, grown in media (water activity (aw) 0.93) supplemented with glucose and sucrose. Growth patterns of Z. rouxii in YM broth supplemented with glucose (YMBG) and sucrose (YMBS) were similar, although increased potassium sorbate concentration in both media resulted in decreased growth rates. Growth in YMBS containing potassium sorbate was not as prolific as that in YMBG containing potassium sorbate. Inhibition of growth was indicated by decreased absorbance (at 600 nm) of cells grown in YMBS and in YMBG and YMBS supplemented with potassium sorbate at 600 or 1000 μg/mL. Slight decreases in cell size and alteration of cellular morphology were associated with increased potassium sorbate concentration. Plasmolysis increased as potassium sorbate concentration was elevated in YMBS but not in YMBG. Tolerance of Z. rouxii to potassium sorbate was enhanced by previous adaptation of cells in media with elevated potassium sorbate concentrations. Heat resistance of cells unadapted to potassium sorbate showed little or no increase regardless of culture age, but increased substantially in cells grown in media containing potassium sorbate, particularly YMBS. Key words: Zygosaccharomyces rouxii, potassium sorbate, glucose, sucrose, heat resistance.

Heat Resistance of Vegetative Cells and Asci of Two Zygosaccharomyces Yeasts in Broths at Different Water Activity Values

1987 ◽  
Vol 50 (10) ◽  
pp. 835-841 ◽  
Author(s):  
MARCO F. G. JERMINI ◽  
WILHELM SCHMIDT-LORENZ
Keyword(s):  
Heat Resistance ◽  
Water Activity ◽  
Vegetative Cells ◽  
Decimal Reduction Time ◽  
Reduction Time ◽  
Zygosaccharomyces Rouxii ◽  
Heat Resistant ◽  
Cell Material ◽  
C Value ◽  
D Values

The heat resistance of vegetative cells and asci of two osmotolerant yeasts (Zygosaccharomyces rouxii and Z. bailii) was investigated in two different broths of aw 0.963 and 0.858, respectively. The highest heat resistance was observed with asci of Z. bailii LMZ 108, showing a decimal reduction time (D-value) at 60°C and aw 0.858 of 14.9 min. Asci of Z. rouxii LMZ 100 were less heat resistant (D60°C-value at aw 0.858 = 3.5 min). The heat resistance (D-values) of asci at aw 0.963 proved to be 20- to 50-fold and 5- to 8-fold higher than the D-valucs of the corresponding vegetative cells of Z. rouxii and Z. bailii, respectively. However, the lower the aw of the heating broth, the smaller the differences between heat resistance of asci and that of vegetative cells. Morever, different preparations of the same cell material were found to lead to different heat resistances.

Probabilistic Modeling of Saccharomyces cerevisiae Inhibition under the Effects of Water Activity, pH, and Potassium Sorbate Concentration

2000 ◽  
Vol 63 (1) ◽  
pp. 91-95 ◽  
Author(s):  
A. LÓPEZ-MALO ◽  
S. GUERRERO ◽  
S. M. ALZAMORA
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Logistic Regression ◽  
Water Activity ◽  
Logistic Models ◽  
Potassium Sorbate ◽  
Yeast Growth ◽  
Ph Values ◽  
Proposed Model ◽  
Critical Ph ◽  
Sorbate Concentration

Probabilistic microbial modeling using logistic regression was used to predict the boundary between growth and no growth of Saccharomyces cerevisiae at selected incubation periods (50 and 350 h) in the presence of growth-controlling factors such as water activity (aw; 0.97, 0.95, and 0.93), pH (6.0, 5.0, 4.0, and 3.0), and potassium sorbate (0, 50, 100, 200, 500, and 1,000 ppm). The proposed model predicts the probability of growth under a set of conditions and calculates critical values of aw, pH, and potassium sorbate concentration needed to inhibit yeast growth for different probabilities. The reduction of pH increased the number of combinations of aw and potassium sorbate concentration with probabilities to inhibit yeast growth higher than 0.95. With a probability of growth of 0.05 and using the logistic models, the critical pH values were higher for 50 h of incubation than those required for 350 h. With lower aw values and increasing potassium sorbate concentration the critical pH values increased. Logistic regression is a useful tool to evaluate the effects of the combined factors on microbial growth.

scholarly journals Nitrogen utilisation and growth at reduced water activity by mucoralean fungi present in soil

1999 ◽  
Vol 65 (5-6) ◽  
pp. 407-413 ◽  
Author(s):  
B.O. Seabi ◽  
B.C. Viljoen ◽  
C. Roux ◽  
A. Botha
Keyword(s):  
Water Activity ◽  
Nitrogen Utilisation ◽  
Reduced Water

scholarly journals Effects of water activity on the performance of potassium sorbate and natamycin as preservatives against cheese spoilage moulds

2017 ◽  
Vol 56 (1) ◽  
pp. 85-92 ◽  
Author(s):  
P. Marín ◽  
C. Ginés ◽  
P. Kochaki ◽  
M. Jurado
Keyword(s):  
Sodium Chloride ◽  
Water Activity ◽  
Penicillium Chrysogenum ◽  
Potassium Sorbate ◽  
Mucor Racemosus ◽  
Food Preservatives ◽  
Glycerol Water ◽  
Fungal Inhibition ◽  
Growth Of Fungi ◽  
Different Levels

AbstractThis work investigated the effects of the food preservatives potassium sorbate and natamycin, combined with different levels of ionic (sodium chloride) and non-ioinic (glycerol) water activity (aw), on growth of fungi involved in cheese spoilage. In general, the combined effect of water stress and presence of preservatives enhanced fungal inhibition. However, some doses of potassium sorbate (0.02%) and natamycin (1, 5 and 10 ppm) were able to stimulate growth of Aspergillus varians, Mucor racemosus, Penicillium chrysogenum and P. roqueforti at awvalues in the range of 0.93–0.97. P. solitum was the only species whose growth was consistently reduced by any doses of preservative. The results also showed that sodium chloride and glycerol differentially affected the efficacy of preservatives. This study indicates that awof cheese is a critical parameter to be considered in the formulation of preservative coatings used against fungal spoilage.

Effects of Potassium Sorbate on Postharvest Brown Rot of Stone Fruit

2008 ◽  
Vol 71 (8) ◽  
pp. 1626-1631 ◽  
Author(s):  
R. GREGORI ◽  
F. BORSETTI ◽  
F. NERI ◽  
M. MARI ◽  
P. BERTOLINI
Keyword(s):  
Brown Rot ◽  
Quality Parameters ◽  
Potassium Sorbate ◽  
Antifungal Compound ◽  
Kinetic Activity ◽  
Acceptable Quality ◽  
Low Toxicity ◽  
Diffusion Assay ◽  
Sorbate Concentration

The effect of potassium sorbate (K-sorb), a low-toxicity chemical, to control Monilinia spp. was investigated. Preliminary in vitro studies found the MIC of K-sorb for conidial germination and mycelial growth was, respectively, 260 and 1,250 mg/liter. Immersion of naturally infected peach and nectarine fruit in a solution (15 g/liter) of K-sorb for 120 s reduced brown rot by over 80% in four of five trials. Although treated fruits showed a significant reduction in firmness with respect to the control, they did not reach the overripe stage and retained acceptable quality parameters. In an attempt to elucidate the mechanism of action for K-sorb, the inhibition of enzymatic activity by K-sorb was also tested. In a radial diffusion assay, the addition of K-sorb to agarose reduced polygalacturonase (PG) activity across the concentrations considered. The greatest reduction (54.3%, with respect to the control) was obtained at a sorbate concentration of 15 g/liter. PG kinetic activity of Monilinia laxa observed by a spectrophotometric assay peaked after 40 min in all samples tested. PG activity was significantly higher in the control than in the samples with increased K-sorb concentrations. In conclusion, based on these findings, K-sorb can be recommended as a low-toxicity antifungal compound against Monilinia spp. in peaches and nectarines with its mode of action probably depending in part on the inhibition of PG activity in M. laxa.

Individual and Combined Effects of Vanillin and Potassium Sorbate on Penicillium digitatum, Penicillium glabrum, and Penicillium italicum Growth

1999 ◽  
Vol 62 (5) ◽  
pp. 541-542 ◽  
Author(s):  
B. MATAMOROS-LEÓN ◽  
A. ARGAIZ ◽  
A. LÓPEZ-MALO
Keyword(s):  
Water Activity ◽  
Inhibitory Concentration ◽  
Synergistic Effects ◽  
Potato Dextrose Agar ◽  
Penicillium Digitatum ◽  
Potassium Sorbate ◽  
Combined Effects ◽  
Fractional Inhibitory Concentration ◽  
Penicillium Italicum ◽  
The Individual

The individual and combined effects of potassium sorbate and vanillin concentrations on the growth of Penicillium digitatum, P. glabrum, and P. italicum in potato dextrose agar adjusted to water activity 0.98 and pH 3.5 were evaluated. Inhibitory concentrations of potassium sorbate varied from 150 ppm for P. digitatum to 700 ppm for P. glabrum, and for vanillin from 1,100 ppm for P. digitatum and P. italicum and 1,300 ppm for P. glabrum. Fractional inhibitory concentration (FIC) isobolograms show curves deviated to the left of the additive line. Calculated FIC index varied from 0.60 to 0.84. FIC index as well as FIC isobolograms show synergistic effects on mold inhibition when vanillin and potassium sorbate are applied in combination.

scholarly journals Phenotypic and Transcriptomic Analyses Demonstrate Interactions between the Transcriptional Regulators CtsR and Sigma B in Listeria monocytogenes

2007 ◽  
Vol 73 (24) ◽  
pp. 7967-7980 ◽  
Author(s):  
Yuewei Hu ◽  
Sarita Raengpradub ◽  
Ute Schwab ◽  
Chris Loss ◽  
Renato H. Orsi ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Stress Response ◽  
Heat Resistance ◽  
Parent Strain ◽  
Inducible Promoter ◽  
Heat Sensitivity ◽  
Intestinal Epithelial ◽  
Class Iii ◽  
Stress Response Genes ◽  
Genes Encoding

ABSTRACT Listeria monocytogenes σB positively regulates the transcription of class II stress response genes; CtsR negatively regulates class III stress response genes. To identify interactions between these two stress response systems, we constructed L. monocytogenes ΔctsR and ΔctsR ΔsigB strains, as well as a ΔctsR strain expressing ctsR in trans under the control of an IPTG (isopropyl-β-d-thiogalactopyranoside)-inducible promoter. These strains, along with a parent and a ΔsigB strain, were assayed for motility, heat resistance, and invasion of human intestinal epithelial cells, as well as by whole-genome transcriptomic and quantitative real-time PCR analyses. Both ΔctsR and ΔctsR ΔsigB strains had significantly higher thermotolerances than the parent strain; however, full heat sensitivity was restored to the ΔctsR strain when ctsR was expressed in trans. Although log-phase ΔctsR was not reduced in its ability to infect human intestinal cells, the ΔctsR ΔsigB strain showed significantly lower invasion efficiency than either the parent strain or the ΔsigB strain, indicating that interactions between CtsR and σB contribute to invasiveness. Statistical analyses also confirmed interactions between the ctsR and the sigB null mutations in both heat resistance and invasion phenotypes. Microarray transcriptomic analyses and promoter searches identified (i) 42 CtsR-repressed genes, (ii) 22 genes with lower transcript levels in the ΔctsR strain, and (iii) at least 40 genes coregulated by both CtsR and σB, including genes encoding proteins with confirmed or plausible roles in virulence and stress response. Our data demonstrate that interactions between CtsR and σB play an important role in L. monocytogenes stress resistance and virulence.

scholarly journals Effect of Water Activities of Heating and Recovery Media on Apparent Heat Resistance of Bacillus cereusSpores

2001 ◽  
Vol 67 (1) ◽  
pp. 317-322 ◽  
Author(s):  
Louis Coroller ◽  
Ivan Leguérinel ◽  
Pierre Mafart
Keyword(s):  
Heat Treatment ◽  
Heat Resistance ◽  
Water Activity ◽  
Effect Of Water ◽  
Optimal Value ◽  
Negative Effect ◽  
The Difference ◽  
D Values ◽  
Recovery Medium ◽  
Heating Medium

ABSTRACT Spores of Bacillus cereus were heated and recovered in order to investigate the effect of water activity of media on the estimated heat resistance (i.e., the D value) of spores. The water activity (ranging from 0.9 to 1) of the heating medium was first successively controlled with three solutes (glycerol, glucose, and sucrose), while the water activity of the recovery medium was kept near 1. Reciprocally, the water activity of the heating medium was then kept at 1, while the water activity of the recovery medium was controlled from 0.9 to 1 with the same depressors. Lastly, in a third set of experiments, the heating medium and the recovery medium were adjusted to the same activity. As expected, added depressors caused an increase of the heat resistance of spores with a greater efficiency of sucrose with respect to glycerol and glucose. In contrast, when solutes were added to the recovery medium, under an optimal water activity close to 0.98, a decrease of water activity caused a decrease in the estimated D values. This effect was more pronounced when sucrose was used as a depressor instead of glycerol or glucose. When the heating and the recovery media were adjusted to the same water activity, a balancing effect was observed between the protective influence of the solutes during heat treatment and their negative effect during the recovery of injured cells, so that the overall effect of water activity was reduced, with an optimal value near 0.96. The difference between the efficiency of depressors was also less pronounced. It may then be concluded that the overall protective effect of a decrease in water activity is generally overestimated.

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