Purification and characterization of a novel neutral β-glucanase and an alkaline β-glucanase from an alkaliphilic Bacillus isolate

摘要

A relatively high β-glucanase-producing strain Bacillus sp. III-3 was isolated from soda lakes in Neimenggu, China. This alkaliphilic strain was found to produce two thermostable β-glucanases including a novel neutral β-glucanase III-3-A and an alkaline β-glucanase III-3-B. The β-glucanases were purified to homogeneity from the culture supernatant with a two-step column chromatographic procedure. III-3-A and III-3-B had molecular mass of approximately 45 and 85 kDa, respectively. Mass spectrometry analysis indicated that III-3-A was probably different from the β-glucanases reported, whereas III-3-B showed high homology with those of family A5 alkaline β-glucanases from alkaliphilic bacilli. The optimum pH of III-3-A was about 7.0, while that of III-3-B was 8.0–10.0. Both enzymes exhibited maximum activity at 45 °C and were stable up to 50 °C. Ca2+ ion stimulated the activity of III-3-A but enhanced the thermostability of III-3-B. The two enzymes were resistant to most metal ions and reagents examined.