Characterization of an organic-solvent-stable elastase from Pseudomonas indica and its potential use in eggshell membrane hydrolysis

Abstract

Abstract The eggshell-membrane (ESM)- and elastin-orcein hydrolyzing activities of an elastase (LasB_indica) isolated from Pseudomonas indica NBRC103045 were demonstrated. The enzyme has 69% homology with a previously reported ESM-degrading elastase from P. aeruginosa ME-4. The gene encoding LasB_indica was cloned and then heterologously expressed in Escherichia coli. Recombinant LasB_indica (rLasB_indica) purified to homogeneity refolded into its active form following acetone treatment. rLasB_indica was stable in organic solvents such as DMSO, ethanol, acetone, 2-propanol, ethyl acetate, and hexane. The optimal reaction conditions for hydrolysis were 45 °C for 15 h in 20 mM Tris−HCl buffer (pH 8.0) containing 0.8 units of rLasB_indica, 7 mM sodium sulfite, and 450 mg of ESM in a 30-ml reaction volume. Hydrolysate production by rLasB_indica was superior to that by the previously reported LasB_ME4 under the tested conditions. Size-exclusion chromatography indicated that the filtered hydrolysate contained soluble peptides with molecular masses ranging between 400 Da and 5 kDa. Further fractionation on a Toyopearl HW-40 gel filtration column produced five main fractions at 280 nm, including two fractions with high ABTS- and DPPH-scavenging activities as well as tyrosinase-inhibiting activity and one fraction with ferric-ion reducing power. Thus, rLasB_indica can be applied to obtain bioactive soluble peptides from ESM.