Tolerance of freeze-dried autochthonous Lacticaseibacillus paracasei to food-related stress factors using by-product-based media

Abstract

The production of dried cultures of lactic acid bacteria (LAB) at low cost and in a sustainable form is relevant for the elaboration of fermented foods and beverages. Lacticaseibacillus paracasei UNQLpc10 was grown in whey permeate and beer lees (WP-BL), then freeze-dried, and its tolerance to different stress factors, low pH, salt, ethanol and lysozyme, was studied. UNQLpc10 grown in this sustainable medium was dried either with or without the same medium and maltodextrin (MD). Cell survival was assessed after freeze-drying and following inoculation under stress conditions. The recovery of viable cells was influenced by the rehydration medium, with rich nutrient media such as MRS and, to a lesser extent, WP-BL, proving necessary for effective cell repair and maintenance of viability under harsh conditions. In contrast, rehydration with physiological solution resulted in high susceptibility and a significant loss of viability. UNQLpc10 can be cultivated in by-product-based media, frozen at −20 °C in the same medium supplemented with buffer and MD (without centrifugation), freeze-dried, and later rehydrated in the same medium, demonstrating good tolerance to stress. This study highlights the potential of combining local LAB strains with agro-industrial by-products and outlines future directions, including evaluation under combined stressors and in real food matrices.