Conservación de cepas microbianas por el método de liofilización para el control microbiológico en Laboratorios Liorad

Abstract

Freeze drying is one of the most popular methods used for the preservation of microorganisms. One of the
many advantages of this method is the prolonged survival time. The selection of additives to achieve a good appearance
as a long-term stability of the freeze dried material is one of the most important aspects to take into the consideration
when you are using this method. The objective of this job was to evaluate the results of the conservation of the microbial
strains Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa by drying method for a
period of five years. For the growth of the strains it was used the tryptone soya broth, skim milk and 20 % glycerol as
lyoprotector substances. Viability, purity and identity were evaluated of each of these strains. The characteristics of these
species remained unchanged with a high degree of purity. The strains in skim milk to 20 %, during this time of observation,
retained viability at adequate levels. The glycerol at 20 % was a good lyoprotector substance for the Staphylococcus
aureus, Escherichia coli and Bacillus subtilis strains to maintain the stability of the viability; however a decrease to the
three years was showed for the survival of the Pseudomonas aeruginosa. The conservation by freeze-drying is a method
of great utility in the work of the collections of cultivation employed to microbiological control.