Diversidade e caracterização probiótica de leveduras encontradas no trato gastrointestinal de bovinos

Abstract

The use of yeasts as a feed supplement for cattle can promote development and improve host performance. However, for the positive results to be consistent, strains with desirable probiotic properties must be selected. The objective of the present study was to isolate and identify yeasts present in the intestine of cattle and, together with strains previously isolated from the rumen (preliminary study), to evaluate their probiotic potential for cattle. A total of 193 strains were studied, including 139 strains (belonging to 19 species) isolated from fecal samples from 11 different animals and 54 strains previously isolated from rumen fluid. The yeast population in the feces ranged from 3.51 to 4.99 log CFU/g, with Candida paraugosa being the most abundant and frequent (isolated from the feces of six of the eleven samples analyzed). Strains were selected that were negative results in the safety tests (hemolytic activity, DNAse, and gelatinase) and had percentages greater than 35 and 70% for hydrophobicity and autoaggregation, respectively. None of the strains evaluated produced antipathogenic metabolites, but strains with a percentage of coaggregation greater than 77.7 and 74.7% were selected, which were pathogenic strains of Escherichia coli and Clostridium perfringens, respectively. The strains that had a percentage of growth relative to 39ºC greater than 61% and viability greater than 96.7% were selected for survival testing under the gastrointestinal conditions of cattle. After the tests, the seven best strains were selected, belonging to the species Candida paraugosa (L60, CCMA 928, and CCMA 930) and Pichia kudriavzevii (isolated L97, L100, CCMA904, CCMA 907). The selected strains did not show the ability to produce cellulolytic, amylolytic, or proteolytic enzymes, but are exopolysaccharide producers. Based on the results of the evaluated properties, the seven selected strains were classified as potential probiotics for cattle.