Survival of strains of lactic acid bacteria in lyophilized probiotic preparations

Cilj ovog rada je priprema funkcionalnih starter kultura, namijenjenih za proizvodnju fermentiranih mliječnih proizvoda, u liofiliziranom obliku, te odabir lioprotektora koji će omogućiti najpovoljnije uvjete provođenja liofilizacije. Liofilizacija se često navodi kao najpogodnija metoda priprave bakterijskih stanica za čuvanje kroz duži vremenski period. Stoga je u ovom radu provedena liofilizacija 12 različitih sojeva bakterija mliječne kiseline koji su okarakterizirani kao funkcionalne starter kulture uz primjenu različitih lioprotektora: obranog mlijeka, inulina i fruktooligosaharida. Indirektnom metodom, prije i nakon liofilizacije, određen je postotak preživljavanja ispitivanih bakterija. Iako se postotak preživljavanja probiotičkih sojeva međusobno razlikuje s obzirom na odabrani lioprotektor, može se zaključiti da većina sojeva ipak zadržava najveći broj živih stanica kada je obrano mlijeko korišteno kao lioprotektor, u usporedbi s uzorcima kada su inulin, te inulin s fruktoolisahardima dodani kao lioprotektori.The aim of this work is functional starter cultures preparation as lyophilized cultures, intended for their production in fermented dairy products, and selection of the optimal lyoprotectant which will the most favourable for strains viability during the freeze-drying. Lyophilization is often referred as the most appropriate method for preparation of bacterial cells for longer period time storage. Therefore, in this work lyophilization of the 12 different strains of lactic acid bacteria, which are characterized as functional starter was conducted by using three different lyoprotectants: skim milk, inulin and inulin with fructooligosaccharides. The percentage of bacterial survival was determined by indirect method, before and after lyophilization. Although viable cell counts varied depending of probiotic strain and lyoprotector applied, it can be concluded that most of the strains survive in high level of cell counts when skim milk was used as lyoprotector compared to the samples where inulin, or inulin in combination with fructooligosaccharides were added as lyoprotectors