Détection de bactéries lactiques produisant du 3-hydroxypropionaldéhyde (précurseur d'acroléine) à partir du glycérol par tests moléculaires

Detection of lactic acid bacteria producing 3-hydroxypropionaldehyde (acrolein precursor) from glycerol by molecular tests. Glycerol, one of the major product of yeasts metabolism during cider and wine alcoholic fermentation is important for sensorial quality of fermented bever- ages. Some lactic acid bacteria convert glycerol to 3-hydroxypropionaldehyde by glycerol dehy- dratase. This reaction originates acrolein which produces bitter compounds by combination with tannins. Thirty nine strains of lactic acid bacteria were isolated from spoiled ciders where glycerol was totally degraded. Lactobacillus collinoideswas the dominant isolated species, Lactobacillus hilgar- dii and Lactobacillus yamanashiensis (Lb . mali) were also identified. Glycerol dehydratase activity was shown. Two oligonucleotide primers (GD1 and GD2) were chosen in the most conserved encod- ing region of one of the glycerol dehydratase subunit of Citrobacter freundii, Klebsiella pneumoniae, Klebsiella oxytoca, Salmonella typhimuriumand Clostridium pasteurianum. The primers led to a 279 bp amplicon (GD) in PCR amplification with the genomic DNA of Lb. collinoides IOEB 9527 as template. The amino acid sequence deduced from the amplicon nucleotide sequence showed a very high similarity with the glycerol dehydratase genes of Gram negative and Cl. pasteurianum species. PCR using GD1 and GD2 primers, only revealed Lb. collinoides strains and Lb. hilgardii strains, which degrade glycerol. The amplified fragment was used as DNA probe in dot-blot hybridiza- tion with the genomic DNA of all the isolated strains from ciders. Only glycerol-degrading strains hybridized. The same probe allowed to isolate glycerol-degrading lactic acid bacteria strains from wine by colony hybridization. Moreover with GD1 and GD2 a 279 bp fragment was also amplified from genomic DNA of those wine strains. Some were Lb. hilgardii strains others could not be identified yet. lactic acid bacteria / glycerol / acrolein