Molecular method for direct detection of exopolysaccharide producer bacteria in spoiled cider

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

Egmond an Zee

Simposio; VIII SYMPOSIUM ON LACTIC ACID BACTERIA: GENETICS, METABOLISM AND APPLICATIONS; 2005

Abstract Exopolysaccharide (EPS) produccion by lactic acid bacteria is benefical in the dairy and oat-based food industries and is used to improve the texture of the fermented products. However, these EPS have a deletereous effect on the viscosity of cider, wine and beer. 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 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. Structural characterisation of the exopolysaccharide revealed that this strain synthesises a 2-substituted-(1-3)- ß-D-glucan. The plasmidic gtf gene from Pediococcus parvulus 2.6 has been cloned and its DNA sequence determined. The gtf gene product is homologous to the members of COG1215 membrane-bound glycosyltranferase family PCRs amplifications and southern blot hibridization showed that the gtf gene is also present at different genomics locations in Lactobacillus diolivorans G77 and Oenococcus oeni I4 strains also isolated from ropy cider, which produces the same EPS than P. parvulus 2.6. A protocol for direct PCR analysis of colonies has been developed. A forward and reverse primers included respectively in the coding sequences of the putatives glycosyltransferase domain and the fifth transmembrane segment of the GTF, were designed. Its usage has allowed identification of new Pediococcus, Lactobacillus and Oenococcus ropy strains isolated from cider, which have the gtf gene. Finally, a method for detection of ropy bacteria in cider has been standardised.