Bio-detoxification of mycotoxins by lactic acid bacteria from different food matrices

摘要

Lactic acid bacteria (LAB) play a key role in the biopreservation of a wide range of fermented food products, suchas yogurt, cheese, fermented milks, meat, fish, vegetables (sauerkraut, olives and pickles), certain beer brands, wines andsilage, allowing their safe consumption, which gave to these bacteria a GRAS (Generally Recognised as Safe) status. Besidesthat, the use of LAB in food and feed is a promising strategy to reduce the exposure to dietary mycotoxins, improving theirshelf life and reducing health risks, given the unique mycotoxin decontaminating characteristic of some LAB. Mycotoxinspresent carcinogenic, mutagenic, teratogenic, neurotoxic and immunosuppressive effects over animals and Humans, being themost important ochratoxin A (OTA), aflatoxins (AFB1), trichothecenes, zearalenone (ZEA), fumonisin (FUM) and patulin. In aprevious work of our group it was observed OTA biodegradation by some strains of Pediococcus parvulus isolated from Dourowines. So, the aim of this study was to enlarge the screening of the biodetoxification over more mycotoxins besides OTA,including AFB1, and ZEA. This ability was checked in a collection of LAB isolated from vegetable (wine, olives, fruits andsilage) and animal (milk and dairy products, sausages) sources. All LAB strains were characterized phenotypically (Gram,catalase) and genotypically. Molecular characterisation of all LAB strains was performed using genomic fingerprinting by MSP-PCR with (GTG)5 and csM13 primers. The identification of the isolates was confirmed by 16S rDNA sequencing. To study theability of LAB strains to degrade OTA, AFB1 and ZEA, a MRS broth medium was supplemented with 2.0 g/mL of eachmycotoxin. For each strain, 2 mL of MRS supplemented with the mycotoxins was inoculated in triplicate with 109 CFU/mL. Theculture media and bacterial cells were extracted by the addition of an equal volume of acetonitrile/methanol/acetic acid(78:20:2 v/v/v) to the culture tubes. A 2 mL sample was then collected and filtered into a clean 2 mL vial using PP filters with0.45 m pores. The samples were preserved at 4 °C until HPLC analysis. Among LAB tested, 10 strains isolated from milk wereable to eliminate AFB1, belonging to Lactobacillus casei (7), Lb. paracasei (1), Lb. plantarum (1) and 1 to Leuconostocmesenteroides. Two strains of Enterococcus faecium and one of Ec. faecalis from sausage eliminated ZEA. Concerning tostrains of vegetal origin, one Lb. plantarum isolated from elderberry fruit, one Lb. buchnerii and one Lb. parafarraginis bothisolated from silage eliminated ZEA. Other 2 strains of Lb. plantarum from silage were able to degrade both ZEA and OTA, and1 Lb. buchnerii showed activity over AFB1. These enzymatic activities were also verified genotypically through specific genePCR and posteriorly confirmed by sequencing analysis. In conclusion, due the ability of some strains of LAB isolated fromdifferent sources to eliminate OTA, AFB1 and ZEA one can recognize their potential biotechnological application to reduce thehealth hazards associated with these mycotoxins. They may be suitable as silage inoculants or as feed additives or even in foodindustry.