| Abstract | U ovom radu provedena je liofilizacija probiotičkih sojeva izoliranih iz tradicionalno proizvedenih sireva. Za zadržavanje visokog broja metabolički aktivnih bakterijskih stanica nakon liofilizacije, jedan od najvažnijih parametara je odabir učinkovitog lioprotektora, odnosno medija za provođenje liofilizacije stanica. Prilikom provođenja liofilizacije, u ovom radu, korištena su tri različita lioprotektora, obrano mlijeko, inulin, te inulin koji sadrži fruktooligosaharide, kako bi se odredili lioprotektori koji doprinose najvećem broju živih aktivnih bakterijskih stanica u konačnom liofiliziranom pripravku. Od ukupno ispitivanih dvanaest sojeva odabrana su tri probiotička soja za daljnja istraživanja: Lactobacillus sucicola BGGO7-28, Lactobacillus casei BGGO5-7, Lactobacillus plantarum ZG2-25, koji su prema rezultatima pokazali najviši broj živih stanica (CFU ml-1) određen nakon liofilizacije. U daljnjim eksperimentima ispitani su najpovoljniji uvjeti liofilizacije bakterijskih stanica s obzirom na lioprotektore: obrano mlijeko, obrano mlijeko uz dodatak saharoze i obrano mlijeko uz dodatak manitola, temperaturu (-20 °C; 4 °C; 21 °C; 37 °C) i trajanje skladištenja (14, 21 i 45 dana), te na korištene otopine za resuspendiranje stanica nakon liofilizacije (fosfatni pufer, MRS hranjiva podloga i obrano mlijeko). Preživljavanje bakterijskih stanica nakon liofilizacije razlikovalo se ovisno o probiotičkom soju, no prema rezultatima uočeno je da dodatak lioprotektora ima zaštitni učinak prilikom liofilizacije stanica u usporedbi s kontrolnim uzorcima. Prema rezultatima određenim za preživljavanje bakterijskih stanica sva tri soja, MRS hranjiva podloga se pokazala kao najučinkovitija otopina za resuspendiranje stanica nakon liofilizacije, dok temperatura skladištenja nije značajno utjecala na preživljavanje bakterijskih stanica. |
| Abstract (english) | Freeze-drying of probiotic strains, derived and isolated from traditionally produced dairy cheeses, was undertaken in this study. One of the most important parameters, for the retention of a high number of metabolically active bacterial cells after freeze-drying, is the selection of an effective lyoprotectant, meaning the most appropriate medium for carrying out the process of cell lyophilization. During the processes of lyophilization carried out in the course of this study, three different lyoprotectants were used - skimmed milk, inulin and inulin with fructooligosaccharides - in order to establish which of the three lyoprotectants results in the highest number of live, active bacterial cells in the final freeze-dried product. Of the twelve strains tested, three probiotic strains were chosen for further research (Lactobacillus sucicola BGGO7-28, Lactobacillus casei BGGO5-7, Lactobacillus plantarum ZG2-25), as the test results indicated that their use resulted in the highest yield of live cells (CFU ml-1) after freeze-drying. In further experiments, tests were carried out to establish the optimum conditions for freeze-drying of bacterial cells taking into account the chosen lyoprotectant (skimmed milk, skimmed milk supplemented with sucrose, skimmed milk supplemented with manitol), temperature (-20 °C; 4 °C; 21 °C; 37 °C), length of storage (14, 21 and 45 days) and use of the rehydration medium (phosphate buffer saline, MRS nutrient medium and skimmed milk). Though viability of the freeze-dried product differed between strains, the results showed that the addition of lyoprotectants had a protective effect during the lyphilization when compared with control samples. Further, taking into account the conditions determined to best aid with maintaining the viability of cells of all three strains during lyophilization, MRS nutrient medium was determined as the most efficient for rehydration. Further, storage temperature did not significantly affect the viability of the bacterial cells. |
