Abstract

Scopulariopsis candida strains LMK004 and LMK008 previously isolated from a solar saltern were cultivated in Vogel’s medium supplemented with NaCl and locust bean gum galactomannan as carbon source and inducer for b-mannannase production. S. candida LMK004 produced up to 180 nkat/ml whereas LMK008 produced 116 nkat/ml. These levels dropped significantly when a-cellulose was used as carbon source. Both enzymes were partially purified by ammonium sulphate precipitation and anion-exchange chromatography. The molecular mass of LMK004 and LMK008 b-mannanases were estimated to be 41 and 28 kDa, respectively.  The b-mannanase from LMK004 was most active at pH 5 and 50°C, and retained ³ 80% of its activity at pH 5 – 6.5 after 24 h of incubation at 4°C. In contrast, the LMK008 b-mannanase retained ³ 60% activity between pH 6 – 7.  Both enzymes remained stable for 3 h between 30 and 40°C, and showed loss of activity at higher temperatures. The LMK008 b-mannanase tolerated high NaCl concentrations with 70% activity remaining after incubation for 2 h at 20% NaCl, whereas the LMK004 b-mannanase was only active between 0 - 10% NaCl. The current study shows that fungi that inhabit hypersaline environments produce plant cell wall degrading enzymes that display similar properties to other fungi from low-salt environments.

Key words: Endo-b-1,4-mannanase, halophiles, mannan, Scopulariopsis candida, solar salterns