Effects of whey protein concentrate on the growth of microorganisms for their potential inclusion in vaginal probiotic products

CAROLINA I. SARALEGUI DUHART; MARÍA SILVINA JUÁREZ TOMÁS; MARÍA ELENA FÁTIMA NADER-MACÍAS

San Miguel de Tucumán, Tucumán, Argentina

Simposio; III Simposio Internacional de Bacterias Lácticas. Segundo Encuentro Red BAL Argentina; 2009

CERELA-CONICET

Lactobacilli are the predominant microorganisms of vaginal microbiota of healthy women and can be applied in pharmaceutical probiotic products to restore the balance of female urogenital tract. During the industrial production of microbial biomass for probiotic products, culture media containing inexpensive components are required in order to increase the yield and decrease the costs. Thus, the aim of this work was to evaluate the growth of potentially probiotic vaginal lactobacilli in low cost culture media. Four microorganisms, isolated from human vagina, were previously selected for their ability to inhibit the growth of uropathogens by antimicrobial substances (lactic acid, hydrogen peroxide and/or bacteriocin). The strains evaluated were: Lactobacillus spp. CRL (from the CERELA Culture Collection) 1263, Lactobacillus spp. CRL 1251, Lactobacillus spp. CRL 1294 and Lactobacillus salivarius CRL 1328. The growth of selected microorganisms was studied in several culture media, containing whey protein concentrate (WPC; main components: 35 ± 2% protein, 48 ± 4% lactose), a low cost substrate. Media with different WPC concentrations (2.5, 5 and 10%) were formulated, which were supplemented with the following nutrients: yeast extract (0, 1 and 2%) and glucose (0 and 2%). The cultures were incubated at 37°C; samples were taken at specific time intervals to determine pH (pH meter Digimeter IV; Luftman; Argentina) and colony forming units per ml (CFU/ml) by the plate dilution method. The results indicate that all the strains were able to grow in WPC media alone (without additional nutrients). However, final pH values observed in WPC media were highest than those reached in conventional culture media (LAPTg or MRS). When WPC media were supplemented with other nutrients, higher acidification rates of lactobacilli cultures, and in some cases lower final pH values, were obtained in growth media containing yeast extract, either in presence or absence of glucose. One growth medium formulated with 2.5% WPC and 1% yeast extract was selected, because the very low cost and the support of a good growth of the microorganisms assayed. In the medium selected, all vaginal lactobacilli reached the maximal biomass (1-5 x 108 CFU/ml) between 6 and 9 h of incubation, with an increase of number of CFU/ml between 1.5 log units (for Lactobacillus spp. CRL 1294) and 2.5 log units (for Lactobacillus spp. CRL 1263). The growth medium formulated in this work allows a cost reduction (around 80%) in biomass production compared with conventional culture media, which is the principal interest during the elaboration of pharmaceutical probiotic products.