Proteolytic activity of selected strains of lactic acid bacteria

Bakterije mliječne kiseline (BMK) su široko rasprostranjeni mikroorganizmi, te se uobičajeno nalaze u mlijeku i mliječnim proizvodima. Proteolitički sustav BMK važan je za njihov rast u mlijeku, omogućava hidrolizu kazeina te daje doprinos razvoju organoleptičkih svojstava fermentiranih mliječnih proizvoda. Cilj ovog rada je istražiti proteolitičku aktivnost sojeva BMK: Lactobacillus brevis D6, Lactobacillus fermentum D12, Lactobacillus plantarum D13 i Lactococcus lactis ZG7-10. Primjenom API 50 CHL medija identificirani su izolirani sojevi bakterija iz roda Lactobacillus i srodnih rodova. AFLP metodom identificiran je autohtoni soj Lactococcus lactis ZG7-10, koji je prema rezultatima dobivenim Ansonovom metodom određivanja proteolitičke aktivnosti imao najveću proteolitičku aktivnost od svih ispitivanih sojeva BMK. Utvrđeno je također kako spomenuti soj proizvodi najveću koncentraciju mliječne kiseline (gL-1), te najbolje raste u prisutnosti 2,0 , 4,0 i 6,5 % (w/v) NaCl-a. Tricine-SDS-PAGE elektroforezom praćena je hidroliza kazeina u obranom mlijeku kao rezultat proteolitičke aktivnosti odabranih sojeva BMKLactic acid bacteria (LAB) are widespread microorganisms and are commonly found in milk and dairy products. Proteolytic system of LAB is important for their growth in milk, enables casein hydrolysis and contributes to the development of organoleptic properties of fermented dairy products. The aim of this paper is to investigate the proteolytic activity of LAB strains: Lactobacillus brevis D6, Lactobacillus fermentum D12, Lactobacillus plantarum D13 and Lactococcus lactis ZG7-10. Using the API 50 CHL media, isolated strains of bacteria from the genus Lactobacillus and related genera were identified. An autochthonous strain of Lactococcus lactis ZG7-10 was identified by the AFLP method, which according to the results obtained by the Anson method of determining the proteolytic activity had the highest proteolytic activity of all examined LAB strains. It was also found that mentioned strain produces the highest concentration of lactic acid (gL-1), and best grows in the presence of 2,0 , 4,0 and 6,5 % (w/v) NaCl. Casein hydrolysis was monitored by Tricine-SDS-PAGE electrophoresis in skimmed milk as a result of proteolytic activity of selected LAB strains