María Silvina Juárez Tomás, Elena Bru, and María Elena Nader-Macías
The use of probiotic microorganisms has been widely promoted in the last 20 years (1). Probiotics have applied to the gastrointestinal tract as capsules or as fermented milks (2). The characteristics of the strains proposed as probiotics have been published (3) or patented after elaboration of the product.
The first step in designing a probiotic product is to isolate and characterize strains with beneficial properties. Our group has reported the isolation and characterization of 134 strains of lactobacilli from the vagina of women from our city (4). Surface properties and the production of antagonistic substances has also been published. From these studies, certain strains were selected because they shared probiotic characteristics (5-7).
The second step in the design of a pharmaceutical product is to determine the optimal conditions for obtaining the highest amount of viable microorganisms, as well as the best conditions to produce antagonistic substances (8). To perform these types of experiments, laboratory assays can be carried out to determine the optimum conditions in which the microorganisms can be cultured. Growth parameters and optimal growth conditions can be studied by the classical methodology (9) or by the application of alternative methodologies (10-12). Alternative methods have been widely used in the food industry, including experimental designs to test multiple conditions at the same time, complemented by the use of statistical models to evaluate and compare all the conditions tested (13-15).
The object of this chapter is to describe the experimental designs used to study the technological characteristics of vaginal probiotic lactobacilli as well as the application of statistical models for evaluation of the different conditions tested for the production of biomass and antagonistic substances in these bacteria. With this objective in mind, in the present chapter, the following areas are explored:
1. Growth experiments performed to study the effect of temperature, pH, agitation, and culture media on the growth and production of antagonistic substances by vaginal lactobacilli.
From: Methods in Molecular Biology, vol. 268: Public Health Microbiology: Methods and Protocols
Edited by: J. F. T. Spencer and A. L. Ragout de Spencer © Humana Press Inc., Totowa, NJ
2. Fractional and complete factorial experimental designs used to perform the growth experiments.
3. Statistical models applied to evaluate the growth parameters and their modifications under the conditions assayed.
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