Population yields and vegetable juice fermentation of Leuconostoc mesenteroides cultures grown under free-cell or immobilized-cell technologies.
Claude Champagne , N. Gardner, S. Lafleur and T. Savard
Nom de la revue: Food Biotechnology 24(1): 1-18.
Leuconostoc mesenteroides BLAC cultures were produced using classical free-cell fermentation technology and immobilized cell technology (ICT). The ICT process consisted of entrapping the culture in alginate or pectin beads, adding beads to a growth medium and incubating for 14 h to allow growth of the culture inside the beads. Cell populations, survival to freeze drying and specific acidifying activity (SAA) following inoculation in vegetable juices were examined. In free cell fermentations, 1.3 x 10<sup>10</sup> cells/ml were obtained while 1.6 to 2.0 x 10<sup>11</sup> cells/g were found in beads. Total cell counts recovered per fermentor were similar in free-cell and ICT systems. In the ICT process, the free-cell level was <=1%. No difference in population yields were noted between alginate and pectin gels. Survival to freeze drying was between 65 and 80% and not markedly affected by the prior fermentation process nor the alginate or pectin matrix. A methodology was developed to ascertain the free-cell content of freeze dried ICT cultures; data showed that they contained 97.5% of gel-entrapped cells. Freshly prepared free-cell suspensions had 4x higher SAA than comparative free-cell freeze dried cultures. Dried ICT cultures had lower SAA than free-cell equivalents but there was no marked effect of the ICT matrix (alginate or pectin) on SAA. Powders of the ICT culture were ground and sieved to obtain particles ranging from 38 to 1000 mum in diam. The smaller the particle the higher its SAA. Fermentation of vegetable juices or pastes was carried out using free and ICT cultures. In the ICT fermentation the free-cell content of the inoculum represented 2.5% of the total population but this increased to 88% after a 22 h incubation in vegetable juice. Results are discussed in relation to potential benefits of ICT cultures in vegetable fermentations.