Biodiversity of spoilage lactobacilli: Phenotypic characterisation

• 120 Lactobacillus strains of 6 different species and a multitude of sources were tested.
• 20 carbon source-related and 25 preservation-related phenotypic factors were evaluated.
• Growth behaviour was highly strain dependent and not species specific.
• Preservation boundaries can be defined on the basis of the number of strains that are able to grow.
• Phenotypic and genetic data will support the development of future preservation strategies.

Preventing food spoilage is a challenge for the food industry, especially when applying mild preservation methods and when avoiding the use of preservatives. Therefore, it is essential to explore the boundaries of preservation by better understanding the causative microbes, their phenotypic behaviour and their genetic makeup. Traditionally in food microbiology, single strains or small sets of selected strains are studied. Here a collection of 120 strains of 6 different spoilage related Lactobacillus species and a multitude of sources was prepared and their growth characteristics determined in 384-well plates by optical density measurements (OD) over 20 days, for 20 carbon source-related phenotypic parameters and 25 preservation-related phenotypic parameters. Growth under all conditions was highly strain specific and there was no correlation of phenotypes at the species level. On average Lactobacillus brevis strains were amongst the most robust whereas Lactobacillus fructivorans strains had a much narrower growth range. The biodiversity data allowed the definition of preservation boundaries on the basis of the number of Lactobacillus strains that reached a threshold OD, which is different from current methods that are based on growth ability or growth rate of a few selected strains. Genetic information on these microbes and a correlation study will improve the mechanistic understanding of preservation resistance and this will support the future development of superior screening and preservation methods.