Solute stresses affect growth patterns, endogenous water potentials and accumulation of sugars and sugar alcohols in cells of the biocontrol yeast Candida sake.
OBJECTIVE
To evaluate the effect of modifications of water activity (aw 0. 996-0.92) of a molasses medium with different solutes (glycerol, glucose, NaCl, proline or sorbitol) on growth, intracellular water potentials (psi(c)) and endogenous accumulation of polyols/sugars in the biocontrol yeast Candida sake.


RESULTS
Modification of solute stress significantly influenced growth, psi(c) and accumulation of sugars (glucose/trehalose) and polyols (glycerol, erythritol, arabitol and mannitol) in the yeast cells. Regardless of the solute used to modify aw, growth was always decreased as water stress increased. Candida sake cells grew better in glycerol- and proline-amended media, but were sensitive to NaCl. The psi(c) measured using psychrometry showed a significant effect of solutes, aw and time. Cells from the 0.96 aw NaCl treatment presented the lowest psic value (- 5.20 MPa) while cells from unmodified media (aw = 0. 996) had the highest value (- 0.30 MPa). In unmodified medium, glycerol was the predominant reserve accumulated. Glycerol and arabitol were the major compounds accumulated in media modified with glucose or NaCl. In proline media, the concentration of arabitol increased. In glycerol- and sorbitol-amended media, the concentration of glycerol rose. Some correlations were obtained between compatible solutes and psi(c).


CONCLUSIONS
This study demonstrates that subtle changes in physiological parameters significantly affect the endogenous contents of C. sake cells. It may be possible to utilize such physiological information to develop biocontrol inocula with improved quality.
Abadias
M
M
Postharvest Unit, CeRTA, Centre UdL-IRTA, Lleida, Catalonia, Spain. isabel.abadias@irta.es
Teixidó
N
N
Usall
J
J
Viñas
I
I
Magan
N
N
D002175:Candida / Q000254:growth & development* / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D003470:Culture Media; D005947:Glucose; D005990:Glycerol; D009997:Osmotic Pressure; D011392:Proline; D012965:Sodium Chloride; D013012:Sorbitol; D013402:Sugar Alcohols / Q000378:metabolism*; D014867:Water
D003470:Culture Media; D013402:Sugar Alcohols; D014867:Water; D012965:Sodium Chloride; D013012:Sorbitol; D011392:Proline; D005947:Glucose; D005990:Glycerol