EFECTO DE LA FUENTE DE CARBONO Y EL PH EN EL CRECIMIENTO Y PRODUCCIÓN DE ÁCIDO LÁCTICO EN Lactobacillus gasseri CRL 1421, POTENCIALMENTE PROBIÓTICO PARA PREVENIR METRITIS BOVINA

M. C. OTERO; M. C. ESPECHE; M. E. NADER-MACIAS

Tucumán, Argentina

Simposio; II Simposio Internacional de Bacterias Lácticas. CERELA-CONICET; 2006

CERELA-CONICET

Metritis in cows reduces the reproductive efficiency, increase herd health costs, reduce feed consumption and also cause an appreciable reduction in milk production. The probiotic lactobacilli therapy could be a valid alternative to the antibiotic application for the treatment of these infections. Lactobacillus gasseri CRL 1421 isolated from bovine vagina was previously studied by its capability to adhere to bovine vaginal epithelial cells, to produce lactic acid and hydrogen peroxide that inhibit the growth of pathogenic microorganisms able to cause metritis. Also can resist the freeze dried process and the storage conditions included in two pharmaceutical forms. The incorporation of this bacteria in a probiotic product requires the study of others technological properties, such as the production of microorganisms at industrial scale, that include the production of biomass at a low cost of production. The aim of this work was to study the effect of different physico-chemical factors on the growth of Lactobacillus gasseri CRL 1421 and to further evaluate the growth conditions in a low cost substrate with high lactose concentration. A complete factorial experimental design of 32 was used to study the effect of carbon sources (glucose, lactose or both) and pH (5.5, 6.5 and 7.5), in LAPTg medium at 37°C. The O.D. at 540 nm was determined at 10 min intervals during 14 h. and the increase of biomass and maximal growth rates were calculated. The lactic acid produced and the carbohydrates concentrations were quantified by HPLC. The experimental procedure was repeated three times following the complete factorial design and the statistical analysis was applied considering the increase of O.D., maximal growth rate, lactic acid production, glucose and lactose consumption in each one of the evaluated conditions. The maximal growth rates were not significantly affected by the initial pH or the carbon source (p<0,05). However, the yield of biomass was significantly (p<0,05) affected by both factors evaluated. The higher increase of biomass was obtained when glucose was the only carbon source, or combined with lactose at pH 6,5. The lactic acid production was significantly affected by the two factors in the assayed conditions (p<0,05) showing interaction between both factors, because the higher concentration was obtained with glucose alone or combined with lactose, depending on the initial pH. The lactose consumption was minimum when glucose was present, except at pH 6,5, results that agree with the high biomass obtained in this condition. The results obtained can be applied for the design of a low cost substrate complemented or based on whey proteins concentrate, supplemented with other carbon sources, to be used for the production of high biomass of probiotic microorganisms.