Lactobacillus fermentum bacteria with antifungal activity

Abstract

The present invention relates to a bacterium of the species Lactobacillus fermentum having the ability to inhibit the growth of the fungus Penicillium solitum deposited under the accession No.: DSM32093 or the growth of the fungus Penicillium brevicompactum deposited under the accession No.: DSM32094 by at least 50%. The inhibitory activity can be determined in an assay comprising: (1) preparing a fermented milk product by: (a) inoculating a milk with the Lactobacillus fermentum in a concentration of at least 10⁷ CFU/g and with a starter culture, (b) fermenting until a p H of 4.6 is reached, and (c) solidifying the fermented milk by the addition of agar; (2) generating at least one spot of the P. solitum or the P. brevicompactum on the agar solidified fermented milk with a concentration of 500 spores/spot and incubating the 1 same for 7 days at 25° C.; (3) determining the percent inhibition by determining the largest diameter of the colony formed by growth of the P. solitum or P. brevicompactum and expressing the diameter as percent of the largest diameter formed under the same conditions but in the absence of the Lactobacillus fermentum strain. The invention further relates to compositions comprising the bacterium, methods for producing fermented milk products using the bacterium and the products thus obtained.

Description

FIELD OF THE INVENTION[0001]The present invention relates to Lactobacillus fermentum bacteria with antifungal activity, compositions comprising the bacteria, in particular adjunct cultures comprising the bacteria, methods of producing a fermented milk product using the bacteria or the cultures and the fermented milk products thus obtained, including food, feed and pharmaceutical products.BACKGROUND OF THE INVENTION[0002]Lactic acid bacteria (LAB) have been used in decades for increasing the shelf life of food products. During fermentation LAB produce lactic acid as well as other organic acids which cause a reduction of pH of the fermented product. Products having an acidic pH do not support further growth of most microorganisms, including pathogenic and spoilage bacteria. However, growth of yeasts and moulds is not affected by low pH and often cause spoilage of fermented dairy products.[0003]In addition to the production of organic acids some LAB also produce metabolites with antimi...

AI Technical Summary

Benefits of technology

[0039]The Lactobacillus fermentum strains of the present invention can for example be characterized in that they increase the pH of a fermented milk product comprising the Lactobacillus fermentum during storage after fermentation in comparison to a milk product fermented with the same starter culture not containing the Lactobacillus fermentum, wherein the increase in pH is at least by a value of 0.1 and is determined after storing the fermented product over 21 days at 25° C., and wherein the starter culture comprises LAB which are able to decrease the pH of a milk product during fermentation to a value of pH 4.6 in 10 hours or less. For example, the assay may be based on mixtures of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. Respective mixtures are frequently used for the production of yoghurt and known to cause post-acidification.

[0040]In a related embodiment a fermented milk product comprising the Lactobacillus fermentum maintains a pH above 4.0 when stored for at least 14 days at 25° C., wherein the fermented milk product is obtained by a method comprising inoculating a milk with the Lactobacillus fermentum in a concentration of at least 107 CFU/g and with a starter culture, fermenting until a pH of 4.6 is reached, shaking the fermented product and cooling. These Lactobacillus fermentum strains of the present invention therefore reduce the post-acidification effect observed in prior art bioprotective cultures and even in conventional starter cultures. It should be understood that the feature specifying that the Lactobacillus fermentum strains of the present invention may maintain the pH above 4.0 when stored for at least 14 days at 25° C. merely characterizes the assay generally used to determine the effect. It is not necessary or required that the Lactobacillus fermentum strains of the present invention, compositions comprising the same, including food or feed products are in fact stored under these conditions. Again, in one aspect the assay can be carried out using a starter culture comprising LAB which are able to decrease the pH of a milk product during fermentation to a value of pH 4.6 in 10 hours or less. For example, the assay may be based on mixtures of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.

[0058](3) determining the percent inhibition by determining the largest diameter of the colony formed by growth of the P. solitum or P. brevicompactum and expressing the diameter as percent of the largest diameter formed under the same conditions but in the

Problems solved by technology

Products having an acidic pH do not support further growth of most microorganisms, including pathogenic and spoilage bacteria.

However, growth of yeasts and moulds is not affected by low pH and often cause spoilage of fermented dairy products.

Developing cultures with antifungal effects represents a big challenge, as it requires the identification of cultures that provide significant antifungal effect i

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