Selection of non-Saccharomyces yeast strains for reducing alcohol levels in wine by sugar respiration.
Respiration of sugars by non-Saccharomyces yeasts has been recently proposed for lowering alcohol levels in wine. Development of industrial fermentation processes based on such an approach requires, amongst other steps, the identification of yeast strains which are able to grow and respire under the relatively harsh conditions found in grape must. This work describes the characterization of a collection of non-Saccharomyces yeast strains in order to identify candidate yeast strains for this specific application. It involved the estimation of respiratory quotient (RQ) values under aerated conditions, at low pH and high sugar concentrations, calculation of yields of ethanol and other relevant metabolites, and characterization of growth responses to the main stress factors found during the first stages of alcoholic fermentation. Physiological features of some strains of Metschnikowia pulcherrima or two species of Kluyveromyces, suggest they are suitable for lowering ethanol yields by respiration. The unsuitability of Saccharomyces cerevisiae strains for this purpose was not due to ethanol yields (under aerated conditions they are low enough for a significant reduction in final ethanol content), but to the high acetic acid yields under these growth conditions. According to results from controlled aeration fermentations with one strain of M. pulcherrima, design of an aeration regime allowing for lowering ethanol yields though preserving grape must components from excessive oxidation, would be conceivable.
Instituto de Ciencias de la Vid y del Vino (CSIC, Universidad de la Rioja, Gobierno de La Rioja), C/Madre de Dios, 51, Logroño, 26006 La Rioja, Spain; Evolva Biotech A/S, Copenhagen, Denmark.
Manuel
M
Quirós
Instituto de Ciencias de la Vid y del Vino (CSIC, Universidad de la Rioja, Gobierno de La Rioja), C/Madre de Dios, 51, Logroño, 26006 La Rioja, Spain; Facultad de Ciencias Químicas, Universidad de Autónoma de San Luis Potosí, Mexico.
Virginia
V
Rojas
Instituto de Ciencias de la Vid y del Vino (CSIC, Universidad de la Rioja, Gobierno de La Rioja), C/Madre de Dios, 51, Logroño, 26006 La Rioja, Spain. Electronic address: rgonzalez@icvv.es.
Ramon
R
Gonzalez
Instituto de Ciencias de la Vid y del Vino (CSIC, Universidad de la Rioja, Gobierno de La Rioja), C/Madre de Dios, 51, Logroño, 26006 La Rioja, Spain.
Pilar
P
Morales
D019342:Acetic Acid / Q000378:metabolism; D000332:Aerobiosis; D050260:Carbohydrate Metabolism; D002241:Carbohydrates; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005516:Food Microbiology; D006863:Hydrogen-Ion Concentration; D013045:Species Specificity; D014920:Wine / Q000032:analysis / Q000382:microbiology*; D015003:Yeasts / Q000378:metabolism*
D002241:Carbohydrates; D000431:Ethanol; D019342:Acetic Acid
Acetic acid; Dealcoholisation; Non-Saccharomyces yeast; Respiratory quotient; Volatile acidity; Wine yeast