Odabir autolitičkih bakterija mliječne kiseline kao mogućih starter kultura za ubrzavanje zrenja sireva u salamuri

The aim of this study was to select lactic acid bacteria (LAB) having autolytic activity on the basis of the technological aspects to accelerate the ripening of white-brined cheeses. For this purpose, mesophilic (n=526) and thermophilic (n=413) LAB isolates were collected from 34 raw milk and 16 cheese samples. 27 LAB isolates with a high autolytic activity ranging from 34 to 54 % were identified by (GTG)5 fingerprint and 16S rDNA sequence analyses, which showed that Lactococcus lactis and Enterococcus faecium were abundant among the autolytic isolates in raw milk while E. faecium and Lactobacillus casei were in white-brined cheese. The autolysis rate of LAB strains increased by raising the temperature and pH; however, decreased somewhat at high NaCl concentrations. Additionally, the highest autolysis was observed in the presence of glucose for most of the strains. On the other hand, Lb. plantarum PFC231 was autolyzed differently, being the highest in the presence of lactose. E. durans PFC235, E. faecium PFC232 and Lb. plantarum PFC231 were autolyzed more than other LAB strains, when exposed to low pH, high NaCI concentration at 10 °C simultaneously. However, only Lb. plantarum PFC231, Leuconostoc mesenteroides PFC234, Lc. lactis subsp. cremoris PFC233, Pediococcus acidilactici PFC237 and Lb. rhamnosus PFC238 were able to show intracellular caseinolytic activity. In conclusion, Lb. plantarum PFC231 has the potential to be used as an adjunct starter culture in the production of white-brined cheeses because of its autolysis at low temperature, pH and high salt concentrations, as well as intracellular caseinolytic activity.Cilj ovog rada bio je odabrati bakterije mliječne kiseline (LAB) koje imaju autolitičku aktivnost, kako bi se upotrebljavale za ubrzavanje procesa zrenja sireva u salamuri. U tu svrhu je iz 34 uzorka sirovog mlijeka te 16 uzoraka sira izolirano 526 mezofilnih i 413 termofilnih sojeva LAB. Primjenom 16SrDNA analize sekvenci i (GTG)5 metode otiska prsta izolirano je ukupno 27 sojeva s autolitičkom aktivnošću koja se kretala između 34 i 54 %. Pritom su se najdominantnijim autolitičkim vrstama u sirovom mlijeku pokazali Lactococcus lactis i Enterococcus faecium, dok su u siru prevladavali Enterococcus faecium i Lactobacillus casei. Stupanj autolize sojeva LAB rastao je s porastom temperature i pH, dok je opadao pri povišenim koncentracijama NaCl. Nadalje, kod svih sojeva je najveća autoliza zabilježena uz prisutnost glukoze. Međutim, soj Lb. plantarum PFC231 ovdje se izdvajao, pokazujući najveću autolizu u prisutnosti laktoze. Sojevi E. durans PFC235, E. faecium PFC232 i Lb. plantarum PFC231 su pri izloženosti niskom pH i visokoj koncentraciji NaCl pri 10 °C pokazivali viši stupanj autolize u odnosu na ostale sojeve. Međutim, samo su sojevi Lb. plantarum PFC231, Leuconostoc mesenteroides PFC234, Lc. lactis subsp. cremoris PFC233, Pediococcus acidilactici PFC237 i Lb. rhamnosus PFC238 pokazali sposobnost unutarstanične hidrolize kazeina. Zaključno, soj Lb. plantarum PFC231 jedini je pokazao potencijal za upotrebu kao starter kultura u proizvodnji sireva u salamuri, budući da ima autolitičku aktivnost pri niskim temperaturama i pH vrijednosti, te visokoj koncentraciji soli, a pokazao je i sposobnost unutarstanične hidrolize kazeina