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 wi ne alcoholic fermentation is important for sensorial quality of fermented b everages. Some lactic acid bacteria convert glycerol to 3-hydroxypropionald ehyde by glycerol dehydratase. This reaction originates acrolein which prod uces bitter compounds by combination with tannins. Thirty nine strains of l actic acid bacteria were isolated from spoiled ciders where glycerol was to tally degraded. Lactobacillus collinoides was the dominant isolated species , Lactobacillus hilgardii and Lactobacillus yamanashiensis (Lb. mali) were also identified. Glycerol dehydratase activity was shown. Two oligonucleoti de primers (GD1 and GD2) were chosen in the most conserved encoding region of one of the glycerol dehydratase subunit of Citrobacter freundii, Klebsie lla pneumoniae, Klebsiella oxytoca, Salmonella typhimurium and Clostridium pasteurianum. The primers led to a 279 bp amplicon (GD) in PCR amplificatio n with the genomic DNA of Lb. collinoides IOEB 9527 as template. The amino acid sequence deduced from the amplicon nucleotide sequence showed a very h igh similarity with the glycerol dehydratase genes of Gram negative and Cl. pasteurianum species. PCR using GD1 and GD2 primers, only revealed Lb. col linoides strains and Lb. hilgardii strains, which degrade glycerol. The amp lified fragment was used as DNA probe in dot-blot hybridization with the ge nomic DNA of all the isolated strains from ciders. Only glycerol-degrading strains hybridized. The same probe allowed to isolate glycerol-degrading la ctic 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 identifi ed yet.