Effect of exogenous proline on the ethanolic tolerance and malolactic performance of Oenococcus oeni
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ORIGINAL ARTICLE
Effect of exogenous proline on the ethanolic tolerance and malolactic performance of Oenococcus oeni Catello Di Martino1 • Bruno Testa1 • Francesco Letizia1 • Massimo Iorizzo1 • Silvia Jane Lombardi1 • Mario Ianiro1 • Massimo Di Renzo1,2 • Daniela Strollo2 Raffaele Coppola1
•
Revised: 27 March 2020 / Accepted: 3 April 2020 Ó Association of Food Scientists & Technologists (India) 2020
Abstract The use of malolactic starter cultures, often offer no guarantee of microbiological success due to the chemical and physical factors (pH, ethanol, SO2, nutrient availability) that occur during the winemaking process. This study was born with the aim of improving the performance of the lactic acid bacteria used as a starter culture in the de-acidification of wines. Two commercial strains of Oenococcus oeni, were used. Was evaluated the effect of exogenous L-proline added during the bacterial growth, on the improvement of their survival in the presence of different ethanol concentrations and their ability to degrade Lmalic acid in synthetic wine with the presence of 12% (v/v) and 13% (v/v) of ethanol. The results showed that L-proline improve ethanol tolerance and so the malolactic performances of O. oeni. This work represents an important strategy to ensure good vitality and improve the performance of the malolactic starter. Keywords L-proline Lactic acid bacteria Ethanol tolerance Malolactic fermentation
Introduction The use of bacteria as starter cultures in the food industry is fundamental for their technological importance, for their metabolic activities and for their possible antimicrobial & Massimo Iorizzo [email protected] 1
Department of Agricultural, Environmental and Food Sciences, University of Molise, Via De Sanctis, 86100 Campobasso, Italy
2
Mastroberardino SpA Winery, Atripalda, AV, Italy
activities, and therefore product stability (De Leonardis et al. 2015; Testa et al. 2019). During food processing bacteria are subject to several stress conditions such as acid environment, high and low temperatures, oxidative stress, osmotic stress, ethanol content, presence of toxic compounds etc. (Van de Guchte et al. 2002), to which they have evolved complex stress responses that can promote their survival under restrictive growth conditions and then improve the performance of the microorganism itself (Baliarda et al. 2003). Bacteria have developed significant strategies to grow and survive under stressful conditions. Stress can be defined as a change in the genome and in the proteome of the bacterium and results in a decrease in the growth rate and its survival. In fact, stress factors can be chemical, physical or biological, some are of environmental origin (temperature, osmotic pressure, pH, ethanol concentration, low availability of nutrients). Therefore, both the physiological state of the cells and the environmental factors will affect the mechanism of stress response. Lactic acid bacteria (LAB) have developed stress detection systems that enable defensive mechanisms to be activated to wi
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