Development of specific probes for detection of glucan-producing lactic acid bacteria

IDOIA IBARBURU; MARÍA LAURA WERNING,; ANA IRASTORZA; MARÍA TERESA DUEÑAS; JESÚS NAVAS; PALOMA LÓPEZ

Portoroz

Simposio; The 19th INTERNATIONAL ICFMH SYMPOSIUM; 2004

Abstract Some lactic acid bacteria produce exopolysaccharides (EPS) and these bacteria or their EPS can be used to enhance the rheology and texture of a variety of food products. However, these EPS have a deletereous effect on the texture of cider and wine. This spoliage of drinks is called oilness or ropyness. Therefore, a method for detection of EPS-producing bacteria could be useful for isolation of new adjuvant strains for food fermentation as well as prevention of ropy spoliage in drinks. We have previously isolated the EPS-producing Pediococcus parvulus 2.6 from ropy cider that improves texture of oat-based fermented products. Structural characterisation of the exopolysaccharide revealed that this strain synthesises a 2-substituted-(1-3)- ß-D-glucan. In this work, the gtf gene from P.damnosus 2.6 has been cloned and its DNA sequence determined. The gtf gene product is homologous to the members of family 2 glycosyltransferases and its catalytic domain is flanked by transmembrane region. Primers were designed to amplify either the N-terminal transmembrane or catalytic domain encoding regions. PCR analysis using these primers demonstrated that Lactobacillus sp. G77, which produces the same EPS than P. damnosus 2.6, also carries the gft gene. Southern analysis revealed that in both bacteria the gene is extrachromosomal. However, a large (35 kb) or small (6 kb) plasmid carries the gene in P. damnosus or Lactobacillus. A protocol for direct PCR anaysis of colonies has been developed. Its usage has allowed identification of new Pediococcus, Lactobacillus and Oenococcus ropy strains isolated from ropy cider, which have the gtf gene. Finally, a method for detection of ropy bacteria in cider has been standardized.