Lactic bacterial strains of the genera Lactobacillus and Pediococcus which are capable of initiating and carrying out a complete malolactic fermentation on direct introduction, in the dried, frozen or lyophilised state, without a previous acclimatization step, at a concentration of between 10.sup.6 and 5.times.10.sup.7 UFC/ml , into a wine with an alcohol content of 10% or more and an average or high pH level. The resistance to alcohol is apparent with an excellent survival rate on inoculation and a rapid start to the fermentation activity such that the strain i) converts at least 5%, preferably at least 10%, of the malic acid into lactic acid in 5 days after inoculation of the wine and ii) converts at least 10%, preferably at least 25%, of the malic acid into lactic acid within 10 days of the inoculation of the wine.