An Adaptation Strategy to Improve the Proteolytic Activities of Lactic Acid Bacteria Isolated From Pickles

Abstract

This study aimed to increase the proteolytic activity of 10 lactic acid bacteria (LAB) species isolated from pickles, which had low activity. For this purpose, a nine-step adaptation through the gradual addition of MRS Broth with peptone and a subsequent four-step adaptation through the gradual addition of MRS Broth with skim milk were applied. A slight improvement of the proteolytic activity following the gradual addition of MRS Broth with peptone was observed only in six LAB samples, of which Pediococcus ethanoliduras 513 showed the highest activity at the ninth step. At the 13 th step corresponding to the last step of the skim milk adaptation, only L. buchneri 114, L. brevis 494, and L. plantarum 380 showed slightly higher activity compared to that at the ninth step. In conclusion, peptone and skim milk adaptations did not yield any industrially significant increase in the proteolytic activity of the 10 LAB strains isolated from pickles. An important increase was only obtained in the proteolytic activity of L. plantarum 380. Its initial activity of 0.095 mM pNA increased to 0.182 mM pNA and finally to 0.250 pNA at the ninth and 13 th steps, respectively, but this increase is too small for industrial applications. Keywords: LAB, proteolytic activity, adaptation, pickles BİTKİ KAYNAKLI LAKTİK ASİT BAKTERİLERİNİN PROTEOLİTİK AKTİVİTELERİNİN GELİŞTİRİLMESİ İÇİN ADAPTASYON ÇALIŞMASI ÖzBu çal›flmada turflulardan izole edilen bitki kaynakl› ve düflük proteaz aktivitesine sahip 10 adet laktik asit bakterisinin proteolitik aktivitesinin art›r›lmas› hedeflenmifltir. Bu amaçla, artan oranda pepton ilave edilmifl MRS Broth besiyerinde 9 aflamal› adaptasyon, ard›ndan süt tozu ilaveli MRS Broth besiyerinde 4 aflamal› adaptasyon gerçeklefltirilmifltir. Pepton adaptasyonunun 9. aflamas›ndan sonra, yaln›zca 6 adet LAB örne¤i bafllang›ca k›yasla bir miktar yüksek aktivite de¤eri göstermifl; bu aflamada en yüksek aktiviteyi Pediococcus ethanoliduras 513 göstermifltir. 13. aflamada (süt tozu adaptasyonu), yaln›zca Lactobacillus buchneri 114, L. brevis 494 ve L. plantarum 380 örneklerinin aktivite de¤erleri 9. aflamaya göre bir miktar artm›flt›r. Sonuç olarak; pepton ve ya¤s›z süt tozuna adaptasyon çal›flmalar›, deneme kapsam›ndaki bitki kaynakl› 10 adet LAB sufluna belirgin bir proteolitik akvite art›fl› kazand›rmam›fl, 13 aflamal› adaptasyon çal›flmas› boyunca yaln›zca L. plantarum 380 örne¤inin proteolitik aktivite de¤erinde, bir miktar art›fl oldu¤u saptanm›flt›r. Bafllang›ç 0.095 mM pNA olan aktivite, 9. aflamada 0.182 mM pNA ve 13. aflamada 0.250 mM pNA de¤erine eriflmifltir. Proteolitik aktivitelerdeki art›fllar, endüstriyel uygulamalar için çok yetersizdir.