Kluyveromyces lactis B10 e Torulaspora delbrueckii B14: características probióticas, mecanismos proteômicos associados, influência no quadro de salmonelose e aplicação em queijo Canastra

Abstract

The use of potentially probiotic microorganisms has been attracting scientific interest, since improvements in the physical, chemical and sensory characteristics of food products have been reported when these microorganisms are used. In addition, probiotic microorganisms provide health benefits to the host, such as reducing glycemic indexes and blood pressure, have antimicrobial effects and improve immune responses to acute and chronic gastrointestinal disorders. However, despite having high biotechnological potential, research using yeasts for this purpose is still limited. Within this context, the objectives of this study were: i) to evaluate the influence of the yeasts Kluyveromyces lactis B10 and Torulaspora delbrueckii B14 on the physical and chemical characteristics of Canastra cheese; ii) to analyze the role of the yeast K. lactis B10, transported to a cheese, in the infection caused by Salmonella Typhimurium in mice and iii) to evaluate the survival of K. lactis B10 and T. delbrueckii B14 in the gastrointestinal tract (GIT), when freeze-dried in UHT milk. The proteins expressed during passage through the GIT were also evaluated. The overall results showed that the yeasts improved the antioxidant characteristics (72.62%) of the cheeses and were able to reduce the lactose content by up to 92.08%. In addition, the cheeses produced with the yeasts presented unique aromatic compounds such as 3-methylbutyl octanoate, phenethyl butyrate, phenethyl propionate, isobutyl butanoate and pentyl propionate that positively contribute to the sensory characteristics of the cheeses. In vivo tests showed the ability of the probiotic cheese to improve the survival and body weight of mice infected with S. Typhimurium. Furthermore, a reduction in the following parameters was observed: translocation to the liver and spleen, intestinal permeability, intestinal IgA levels, and myeloperoxidase (MPO) and eosinophilic peroxidase (EPO) activities in the liver and ileum in animals infected with S. Typhimurium and treated with the probiotic cheese. Safety tests showed that the yeasts are safe for use in the food industry. The survival of the lyophilized yeasts was 83.38% and 75.51% for K. lactis B10 and T. delbrueckii B14, respectively, at 4°C after 120 days. When subjected to simulated GIT conditions, K. lactis B10 showed a viability of 96.72%, while T. delbrueckii showed a viability of 97.75% after 270 minutes of exposure to bile acids and salts. The proteins expressed during passage through the GI tract were proteins involved in carbohydrate and amino acid metabolism, energy production and tolerance to oxidative stress. In addition, proteins involved in the adhesion mechanism were also observed in K. lactis B10. Therefore, these results demonstrate that both yeasts have potential to be used as probiotics in the food industry and provide insights into molecules produced by yeasts and associated with environmental stress.