Proteolytic activity of probiotic starter cultures of lactic acid bacteria

Abstract

Tema ovog rada bila je ispitati proteolitičku aktivnost autohtonih Lactococcus lactis sojeva s ciljem odabira starter kultura za proizvodnju svježeg dimljenog sira. Bakterije mliječne kiseline (BMK) su vrlo važne starter kulture u biotehnološkoj proizvodnji različitih fermentiranih mliječnih proizvoda. Proteolitički sustav ima važnu ulogu u toj proizvodnji jer omogućava rast bakterija mliječne kiseline u mlijeku, odnosno razgradnju kazeina do aminokiselina potrebnih za rast BMK, što pak osigurava uspješnu fermentaciju. Zbog toga je metodom rupama u agaru ispitana proteolitička aktivnost 12 odabranih Lactococcus lactis sojeva, a oni sojevi koji su pokazali najveću proteolitičku aktivnost su izabrani za daljnje ispitivanje Ansonovom metodom. Mjerenjem proteolitičke aktivnosti Ansonovom metodom utvrđeno je da soj L. lactis ZG 7-10 pokazuje znatno bolju aktivnost u odnosu na ostale sojeve te je ispitana njegova sposobnost razgradnje kazeina Tricine SDS-PAGE metodom.The aim of this study was to examine the proteolytic activity of autochtonous Lactococcus lactis strains in order to select starter cultures for smoke fresh cheese production. Lactic acid bacteria are ver important starter culture in biotechnological production of different fermented dairy products. The proteolytic system plays an important role in this production since it allows the growth of lactic acid bacteria in milk, meaning degradation of the casein to the amino acids necessary for the growth of LAB, thus ensuring successful fermentation. Using agar well assay proteolytic activity of 12 selected Lactococcus lactis strains has been tested and strains that expressed stronger proteolytic activity were selected for further testing by Anson's method. Measuring proteolytic activity by Anson's method revealed that L. lactis ZG 7-10 showed a significantly better activity compared to other strains so its ability to degrade casein was tested by Tricine SDS-PAGE method