Efeito da liofilização sobre propriedades probióticas de bactérias ácido-lácticas isoladas do kefir e do polvilho azedo.

Abstract

To be considered probiotics, microorganisms must have several characteristics, among them, they resist the passage through the simulated gastrointestinal tract, have an antagonistic effect against pathogens and be viable and stable during storage. Lyophilization is considered one of the most used and efficient techniques in the preservation of microorganisms, as it maintains high viability of the cells, enabling large-scale industrial production. It is a dehydration technique and occurs under special conditions of pressure and temperature, allowing the previously frozen water to pass to the gaseous state, stabilizing the product. Lyophilization can damage bacterial cells, and it is important to assess the resistance to this drying process. The objective of this work was to evaluate the lyophilization process on probiotic properties of strains isolated from milk and water kefir and sour starch. Antagonistic activity was evaluated using the spot-on-the-lawn method and sensitivity test to conditions of the simulated gastrointestinal tract (pH 2.5 and 0.45 g / L bile) of Leuconostoc mesenteroides 9U2, Lactococcus lactis 3P, Lactobacillus satsumensis 23P3 strains, Lactobacillus perolens 11P3, Lactobacillus perolens 17P2, Lactobacillus brevis A5SC3 and Lactobacillus plantarum A95SC2, for free and lyophilized cells. In addition, the viability of the strains was evaluated for 60 days at lyophilized room temperature. The strains evaluated showed antagonistic action against the pathogens tested in free and lyophilized form. The percentage of survival (in log) to the gastrointestinal conditions of free cells was 100% for the genera Leuconostoc and Lactobacillus and between 95% to 97% for Lactocococcus and Lactobacillus whereas for lyophilized cells of the genera Leuconostoc and Lactobacillus they were from 88 to 96 %. Evaluating the viability for 60 days at room temperature, the lyophilized strains were maintained in final concentrations of 9 to 10 log10 UFC.mL-1. All strains showed inhibitory action against the pathogens tested and viability to pass through the simulated gastrointestinal tract before and after the lyophilization process. Lyophilization did not affect the probiotic characteristics tested, demonstrating that it is a safe drying process to obtain a lyophilized product from lactic acid bacteria isolated from kefir and sour starch. Storage did not significantly affect the final concentration of the tested strains. Strains Leuconostoc mesenteroides 9U2, Lactobacillus perolens 11P3 and Lactobacillus brevis A5SC3, isolated from milk, water and sour starch kefir, respectively, are potentially probiotic, provided that complementary studies are carried out to cover all criteria.