The ability of several lactic acid bacteria (LAB) to inhibit Clostridium botulinum toxigenesis was investigated. Acidification studies identified the bacteriocinogenic strains Lactococcus lactis ATCC 11454 and Pediococcus pentosaceus ATCC 43200 as the most promising based on their ability to rapidly acidify a model gravy system. These two strains, a third bacteriocinogenic strain Lactobacillus plantarum BN, and nonbacteriocinogenic strains as controls were then coinoculated along with C. botulinum type A and B spores into a model gravy system to determine if bacteriocin production and acidification are effective in preventing C. botulinum growth and toxin production. Triplicate tubes of gravy-like media containing either 0 or 0.5% glucose were coinoculated with the LAB at 104 CFU/ml and with the pool of heat-shocked C. botulinum spores at 102, 104, and 106 CFU/ml and incubated anaerobically at 15, 25, or 35°C. The media were monitored for C. botulinum growth, toxin production, and acidity. At 15°C, both the bacteriocinogenic and nonbacteriocinogenic strains of L. lactis and L. plantarum prevented toxigenesis in gravy containing glucose at all C. botulinum inocula levels. The bacteriocinogenic and nonbacteriocinogenic strains of P. pentosaceus prevented toxin production by C. botulinum at 102 and 104 CFU/ml in the presence of glucose. P. pentosaceus 43200 was the only strain tested showing inhibition in the absence of glucose, preventing toxigenesis by C. botulinum at 102 CFU/ml. At 25 and 35°C, none of the lactic acid bacteria tested prevented toxigenesis. The results suggest that acid production by these strains of LAB may afford some protection against mild temperature abuse and that bacteriocin production had little if any additional effect. The biopreservation system was ineffective at temperatures of 25 and 35°C.

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