Determination of the growth stages of Lactobacillus paracasei subsp paracasei M3 from Bulgarian yellow cheese by electroconductivity

The growth curve and the bacteriocin production by Lactobacillus paracasei subsp. paracasei M3-a strain isolated from Bulgarian yellow cheese, was stu died using electroconductivity measurements in the culture medium (MRS). Th e bacteriocin produced by this bacterium inhibits strains belonging to the Candida species as well as Bacillus subtilis ATCC 6633. The use of the direct impedance technique coupled with statistical treatmen t of the results for the strain's growth curve allowed the detection of the growth phase-related bacteriocin production. Definition of the average par ticle size and aggregation estimations for the cells of the bacteriocin-pro ducing strain was also possible. The comparison of results of impedance mea surements with results obtained by classic microbiological methods and micr oscopic observations confirms the good correlation between these methods. I n addition, the advantages of an impedance method such as rapidity, simplic ity and higher sensitivity are highlighted. (C) 2001 Elsevier Science B.V. All rights reserved.