The influence of a cryoprotective medium containing glycerol on the lyophilization of lactic acid bacteria

Abstract

The aims of lyophilization (freeze-drying) of lactic acid bacteria are to preserve pure cultures or to prepare starters for the dairy industry. In both cases, the choice of the cryoprotectant is very important. In this work, samples of Bifidobacterium breve A71 and Bifidobacterium bifidum BbTD were freeze-dried in a new cryoprotective medium containing lactose, gelatin and glycerol (medium B). The reference medium contained saccharose, gelatin and skim milk (medium A). Before lyophilization, the eutectic points of both media were determined, because the products must be cooled to a temperature below its freezing point. The success of the cryoprotectants was estimated in terms of the number of surviving organisms after lyophilization. Bifidobacterium breve A71 and Bifidobacterium bifidum BbTD freeze-dried in media A and B showed high survival rates. Bifidobacterium breve A71 showed a greater percentage survival in combination with medium B than with medium A. These results could be utilized in the manufacture of Bifidobacterium breve A71 as a starter in the diary industry because it is a human isolate which, except for acidification, has probiotic activity.

Bakterije mlečne kiseline se liofilizuju (suše u zamrznutom stanju) sa ciljem čuvanja kultura na duže vreme ili u formi startera za mlečnu industriju. U oba slučaja važan je izbor krioprotektanata. U ovom radu praćena je liofilizacija Bifidobacterium breve A71 i Bifidobacterium bifidum BbTD u novom krioprotektivnom medijumu sa laktozom, želatinom i glicerolom (medijum B). Referentni medijum sadrži saharozu, želatin i obrano mleko (medijum A). Liofilizaciji prethodi određivanje eutektičke temperature jer se faza zamrzavanja odvija na nešto nižoj temperaturi od eutektičke. Efikasnost krioprotektanata ispitivana je u smislu preživljavanja kultura nakon liofilizacije. Bifidobacterium breve A71 i Bifidobacterium bifidum BbTD liofilizovani u medijumima A i B ostaju u visokom procentu vijabilne. Obe kombinacije krioprotektanata daju relativno visok procenat preživljavanja. Bifidobacterium breve A71 u kombinaciji sa medijumom B ima veći procenat preživljavanja nego u kombinaciji sa medijumom A. Ovi rezultati mogu poslužiti u proizvodnji liofilizovanog Bifidobacterium breve A71 - startera u mlečnoj industriji jer je to humani izolat sa potencijalno dobrim probiotskim osobinama.