New Malolactic Bacteria Strains Isolated from Wine Microbiota: Characterization and Technological Properties

Răzvan Vasile Filimon,Claudiu-Ioan Bunea,Simona Isabela Dunca,Roxana Mihaela Filimon,Ancuța Nechita,Andrei Mocan,Florin Dumitru Bora

doi:10.3390/fermentation8010031

Abstract

Malolactic fermentation (MLF) or biological decrease of wine acidity is defined as the enzymatic bioconversion of malic acid in lactic acid, a process performed by lactic acid bacteria (LAB). The procedures for the isolation of new indigenous LAB strains from the red wines produced in Copou Iasi wine center (NE of Romania) undergoing spontaneous malolactic fermentation, resulted in the obtaining of 67 catalase-negative and Gram-positive LAB strains. After testing in the malolactic fermentative process, application of specific screening procedures and identification (API 50 CH), two bacterial strains belonging to the species Oenococcus oeni (strain 13-7) and Lactobacillus plantarum (strain R1-1) with high yield of malolactic bioconversion, non-producing biogenic amines, and with active extracellular enzymes related to wine aroma, were retained and characterized. Tested in synthetic medium (MRS-TJ) for 10 days, the new isolated LAB strains metabolized over 98% of the malic acid at ethanol concentrations between 10 and 14 % (v/v), low pH (>3.0), total SO2 doses up to 70 mg/L and temperatures between 15 and 35 °C, showing high potential for future use in the winemaking process as bacterial starter cultures, in order to obtain high quality wines with increased typicity.

Highlights

It is generally accepted that wine is the result of two biological processes of fermentation—alcoholic and malolactic bioconversions—determined by the microorganisms that develop on grapes during ripening
Considering that in many wine regions of the world the use of lactic acid bacteria (LAB) starter cultures to initiate MLF has not yet become a routine practice and that the typicity of the wines can be much amplified by the use of carefully selected LAB strains, the aim of this work was the characterisation and assessment of technological properties of new malolactic bacteria strains isolated from red wine microbiota, in order to determine their potential to be used as starter cultures to induce the malolactic fermentation of wine
Colonies that were grown on the surface of the agarised MRS medium after the incubation of the wine dilutions were counted, and the number of lactic acid bacteria was calculated in relation to the dilution performed

Summary

Introduction

It is generally accepted that wine is the result of two biological processes of fermentation—alcoholic and malolactic bioconversions—determined by the microorganisms that develop on grapes during ripening. If in the alcoholic fermentation grape sugars are metabolized by yeasts and transformed into ethanol and carbon dioxide, in the case of malolactic fermentation (MLF), under the action of lactic acid bacteria, L-malic acid of wine is decarboxylated to L-lactic acid, with the production of varying concentrations of secondary fermentation metabolites. MLF is one of the most difficult processes to control and can affect the aroma and taste balance of the final product [2]. LAB involved in the winemaking process belongs to the Lactobacillus, Leuconostoc, Oenococcus, and Pediococcus genera, with Oenococcus oeni and Lactobacillus plantarum as the most used species for conducting controlled MLF [4,5,6]. The selection of new LAB for starter cultures requires the assessment of many properties related to the new strain including resistance to biotic and abiotic stresses, technological performances, and safety aspects [7]

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Conclusion