Survival of Bacteria and Fungi in Relation to Water Activity and the Solvent Properties of Water in Biopolymer Gels

Mugnier, J.; Jung, Gérard

doi:10.1128/aem.50.1.108-114.1985

Cited by 147 publications

(49 citation statements)

References 23 publications

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“…As we have observed in our formulations, bacterial contaminations were the most relevant; therefore, lowering a w was an efficient way to control bacterial growth (Mugnier and Jung 1985) and as it is demonstrated in Table 2, glycerol incorporation allowed to preserve a viable count after 6 months under which no contamination was observed.…”

Section: Discussionsupporting

confidence: 58%

Pilot-scale production and liquid formulation of Rhodotorula minuta, a potential biocontrol agent of mango anthracnose

et al. 2005

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Aims: To develop a pilot-plant fermentation process for the production of the yeast Rhodotorula minuta, to be used as a biocontrol agent of mango anthracnose, using a low-cost culture medium. To develop a stable liquid formulation that preserve high viability of the yeast stored at 4°C. Methods and Results: Keeping constant the volumetric power input, a fermentation process was scaled-up from shake flasks to a 100 l bioreactor. Preharvest applications of the yeast resulted in postharvest anthracnose severity equal or lower than that observed with a chemical fungicide. Glycerol was added to the formulation as water activity reducer and xanthan gum as a viscosity-enhancing agent. Yeast initial concentration of 10 10 CFU mlresulted in 4-5 orders of magnitude decrease after 1 month of storage at 4°C, whereas when it was formulated at 10 9 CFU ml )1 , the decrease was of two orders of magnitude in 6 months. Conclusions:The fermentation process was successfully scaled-up using a low-cost culture medium. Postharvest anthracnose severity could be considerably reduced using this yeast. Formulating the yeast at 10 9 CFU ml )1and adding glycerol (20%) and xanthan (5 g l )1 ) avoided both contamination and yeast sedimentation and it was able to preserve up to 10 7 CFU ml )1 after 6 months at 4°C.Significance and Impact of the Study: The yeast R. minuta is reported as a novel antagonistic micro-organism against the pathogen Colletotrichum gloeosporioides. Pilot plant production of this yeast allowed us to conduct field tests in commercial orchards during three harvest seasons. Yeast suspensions applied to mango trees reduced the fruit anthracnose severity in levels similar or better than chemical fungicides.

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Section: Discussionsupporting

confidence: 58%

Pilot-scale production and liquid formulation of Rhodotorula minuta, a potential biocontrol agent of mango anthracnose

et al. 2005

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“…It might be due to storage in uncontrolled a w of the aluminum foil. Under this circumstance, residual water could play the role of a "true solvent" (Mugnier and Jung 1985) which mediates H + to reach bacterial cells more easily leading to cell loss.…”

Section: Resultsmentioning

confidence: 99%

Survival, Acid and Bile Tolerance, and Surface Hydrophobicity of Microencapsulated B. animalis ssp. lactis Bb12 during Storage at Room Temperature

Dianawati

Shah

2011

Journal of Food Science

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Survival, acid and bile tolerance, and surface hydrophobicity of microencapsulated Bifidobacterium animalis ssp. lactis Bb12 were studied during storage at room temperature (25 °C) at low water activity (0.07, 0.1, and 0.2). Two types of alginate-based systems were prepared with and without mannitol as microencapsulant of B. animalis ssp. lactis Bb12. Formation of gel beads containing cells was achieved by dropping each emulsion into CaCl(2) solution; then, the beads were freeze dried. Survival, acid tolerance during 2-h exposure in de Man, Rogosa, Sharpe (MRS) broth at pH 2.0, bile tolerance during 8-h exposure in MRS broth containing taurocholic acid at pH 5.8, and retention of surface hydrophobicity were determined after freeze drying and during storage. The result showed that neither alginate nor alginate-mannitol formulation was effective in protecting B. animalis ssp. lactis Bb12 during freezing and freeze drying. The viability in alginate-mannitol and alginate formulations after freeze drying was 6.61 and 6.34 log CFU/g, respectively. Storage at low a(w) improved survival, acid tolerance, bile tolerance, and surface hydrophobicity retention of microencapsulated B. animalis ssp. lactis Bb12 when compared with controlled storage in an aluminum foil (with a(w) of 0.38 and 0.40 for alginate-mannitol and alginate formulations, respectively). Alginate mannitol was more effective than the alginate system during a short period of storage, but its effectiveness decreased during a long period of storage (80% survival at 10 wk). Nevertheless, storage of microencapsulated B. animalis ssp. lactis Bb12 in an aluminum foil without a(w) adjustment during 10 wk at room temperature was not effective (survival was 64% to 65%).

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“…Reported results vary widely. For example, rhizobia stored in polysaccharide gels survived better at low than at high RH (Mugnier and Jung 1985). Survival of B. japonicum on glass beads was about the same at 0% RH vs 75% RH (Cliquet and Catroux 1994).…”

Section: Discussionmentioning

confidence: 99%

Factors affecting the survival ofBradyrhizobiumapplied in liquid cultures to soya bean [Glycine max(L.) Merr.] seeds

Streeter

2007

Journal of Applied Microbiology

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Aims: To determine the impact of medium composition, bacterial strain, trehalose accumulation, and relative humidity during seed storage on the survival of Bradyrhizobium japonicum on soya bean [Glycine max (L.) Merr.] seeds. Methods and Results: Bacteria in liquid cultures were applied to seeds, and the number of survivors was quantified after 2, 24, 48, or 96 h. Addition of yeast extract to a defined medium increased on-seed survival 50-to 80-fold. Addition of 40 mmol l )1 of NaCl to the medium doubled or tripled the accumulation of trehalose in cells and increased survival several fold, and the addition of both salt and trehalose had an additive effect. There was a threefold difference among strains in survival, and survival of the various strains was significantly correlated with differences in the accumulation of trehalose. The correlation between trehalose accumulation by bacteria and survival was also highly significant in other experiments. Studies in controlled humidity environments showed 100-fold or more differences in survival. Conclusions:The consistently significant correlation of trehalose content of cells with survival on seed suggests that trehalose is an important component of the survival mechanisms. When some of the factors (salt and trehalose in the medium plus humidity control) were studied in combination, several 100-fold increases in survival of bacteria on seeds were recorded. Significance and Impact of the Study: It is possible by manipulation of several parameters -strain selection, salt and trehalose content of the medium, control of relative humidity -to achieve substantial improvements in survival of Bradyrhizobium on soya bean seeds.

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Survival of Bacteria and Fungi in Relation to Water Activity and the Solvent Properties of Water in Biopolymer Gels

Abstract: Survival of bacteria (Rhizobium, Agrobacterium, and Arthrobacter spp.), fungal spores (Penicillium sp.), and yeasts (Saccharomyces sp.) was studied in relation to water activity (aw) and the presence of nutritive solutes.

Cited by 147 publications

References 23 publications

Pilot-scale production and liquid formulation of Rhodotorula minuta, a potential biocontrol agent of mango anthracnose

Pilot-scale production and liquid formulation of Rhodotorula minuta, a potential biocontrol agent of mango anthracnose

Survival, Acid and Bile Tolerance, and Surface Hydrophobicity of Microencapsulated B. animalis ssp. lactis Bb12 during Storage at Room Temperature

Factors affecting the survival ofBradyrhizobiumapplied in liquid cultures to soya bean [Glycine max(L.) Merr.] seeds

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