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Control of malolactic fermentation: Development of lactic acid bacteria for direct inoculation into wine

Objective

The biological decarboxylation of L-malic acid, commonly called malolactic fermentation, is an essential process in quality wine making. Traditionally, the wine maker awaits the growth of special indigenous bacteria which, in ideal cases, attain sufficiently high numbers to transform the L-malic acid just after the alcoholic fermentation. However the process is often delayed or even impossible particularly in very acidic wines.

Control of the malolactic fermentation can be achieved by inoculating the young wine with cultures of lactic acid bacteria. The problem with these readily available industrial preparations is that they can only be used after reactivation, they are not always effective and their application is time and labour consuming.

The aim of this project is to develop efficient malolactic cultures for direct inoculation into wine.
Malolactic fermentation is an essential process in quality winemaking. The objective of the project is to improve the efficiency of malolactic starters, by developing better methods for the selection, characterization and cultivation of strains of Leuconostoc oenos.

The bacteria have been identified by deoxyribonucleic acid (DNA) hybridization and screened for prophages. Strains capable of survival and growth in wine have been selected. The selected strains showed different nutrient demands and malolactic activity. For some of the strains, the composition of the culture medium influenced the lipids of the membranes and their ability to survive direct inoculation into wine. The strains were grouped with respect to sugar utilization and production of acetic acid. rRNA and tRNA have been isolated from the strains. tRNA levels increased whenmalolactic fermentation was stimulated.

The total control of the malolactic fermentation, an essential process in quality winemaking, can be achieved by inoculating the young wine with freeze dried cultures of lactic acid bacteria. At present, the available industrial preparations can only be used after reactivation, they are not always effective and their application is time and labor consuming. The aim of this project is to develop efficient malolactic cultures for direct inoculation into wine.
A large collection of Leuconostoc oenos has been constituted. Some of them are prophage free (ie they do not induce phages after a mitomycin C treatment). More work is necessary to appreciate the actual importance of phage infection in wine. Resistance of bacteria to the environmental toxicity of wine appears to be very different according to the culture conditions. The physiological and/or genetic origin of this resistance must be thoroughly studied as it determines the success of wine inoculation.

The total control of the malolactic fermentation, an essential process in quality winemaking, can be achieved by inoculating the young wine with freeze dried cultures of lactic acid bacteria. At present, the available industrial preparations can only be used after reactivation, they are not always effective and their application is time and labor consuming. The aim of this project is to develop efficient malolactic cultures for direct inoculation into wine.
Our objective has been to study the genetic base of malolactic fermentation. In particular we have investigated several methods to identify and characterize phenotypic mutants to be used as markers in the near future. We have constructed a bank of L oenos deoxyribonucleic acid (DNA) in an Escherichia coli recipient by using the plasmid pbr 322 as a vector.

The total control of the malolactic fermentation, an essential process in quality winemaking, can be achieved by inoculating the young wine with freeze dried cultures of lactic acid bacteria. At present, the available industrial preparations can only be used after reactivation, they are not always effective and their application is time and labor consuming. The aim of this project is to develop efficient malolactic cultures for direct inoculation into wine.
The main objective has been to select the most interesting strains among the hundreds of isolates from France, Italy, Portugal and Spain. The selection was made according to the growth potential, resistance to wine (survival and growth after direct inoculation), malolactic activity, other biochemical and biological effects on the wine, and the organoleptic properties which must be studied in microvinification trials during the production season.
The biological decarboxylation of L-malic acid, commonly called malolactic fermentation, is an essential process in quality winemaking. Traditionally, the winemaker awaits the growth of special indigenous bacteria which in ideal cases attain sufficiently high numbers to transform the L-malic acid just after the alcoholic fermentation. However, the process is often delayed or even impossible, particularly in very acidic wines.

Control of the malolactic fermentation can be achieved by inoculating the young wine with cultures of lactic acid bacteria. The problem with these readily available industrial preparations is that they can only be used after reactivation, they are not always effective, and their application is time, and labour consuming.

The aim of this project is to develop efficient maloactic cultures for direct inoculation into wine. The first part of the work concerns isolation and selection of the appropriate bacteria. As far as possible the necessary wines are provided from various winegrowing regions in Europe and their different origins will ensure a wide variety of bacterial strains. Secondly the principal substrates of the bacterial catabolism (sugars, organic acids) and espacially the formed products will be investigated, first in a synthetic medium, and then in wine. Particular attention will be given to the aromatic components. An organoleptic analysis will be performed in the trials made in wine in order to estimate the impact of the different strains on the wine quality.

At the same time we will investigate the fundamentals of the natural adaptation of the lactic acid bacteria to growth in wine, a characteristic which is quickly lost after isolation of the strains in an optimal medium. Genetic as well as physiological factors may be involved, and we will study the ways of stabilising those. The final phase of the project deals with the parameters which influence the cultivation and preparation of the selected bacteria.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Chr. Hansens Laboratorium A/S
Address
10,Bøge Allé
2970 Hørsholm
Denmark

Participants (2)

UNIVERSITE VICTOR SEGALEN - BORDEAUX II
France
Address
Rue Leo Saignat, 146
33076 Bordeaux
Università degli Studi di Bologna
Italy
Address
42,Via Irnerio
40126 Bologna