Screening, purification, and characterization of proteinase from 3 Lactobacillus delbrueckii subsp. bulgaricus

Abstract

Three strains of Lactobacillus delbrueckii subsp. bulgaricus were selected for their proteinase properties in order to improve milk gel firmness. The respective proteinases were purified by ultra-filtration, anion exchange, and hydrophobic interaction chromatographies. The 3 purified proteinases were determined to have molecular masses of about 39, 40, and 52 kDa. The optimal activities of the purified enzymes occurred at pH 6.0 and 40 °C. They are metallopeptidases, activated by Fe²⁺, inhibited by Ba²⁺, Zn²⁺, Mn²⁺, Xi²⁺, Fe³⁺, Cu²⁺ and EDTA, and serine proteinases which are inhibited by PMSF.