High level production of a novel acidic and thermostable chitinase from Paecilomyces thermophila for the extraction of bioactive components from Ganoderma lucidum spores

A novel acidic exochitinase gene (Ptchi18a) from the thermophilic fungus Paecilomyces thermophila J18 was cloned and expressed in Pichia pastoris. The highest chitinase activity of 75.9 U/mL was obtained by highcell density fermentation, which represents the highest yield for fungal chitinases to date. The recombinant enzyme (Ptchi18a) exhibited maximal activity at pH 5.5 and 60 ℃, respectively. It hydrolyzed colloidal chitin to yield mainly N-acetyl chitobiose (93.6%, w/w), exhibiting a typical exo-type action manner. Ptchi18a efficiently degraded the cell walls of Ganoderma lucidum spores accompany with cellulose for the extraction of bioactive components. The extraction ratios of bioactive polysaccharides, lipids and triterpenoids reached to 3.18%, 16.37% and 1.89% (w/w), respectively, which were 27, 9 and 4 times higher than that without enzymatic pretreatment. The unique properties may make Ptchi18a a good candidate for the bioconversion of chitin materials as well as the bio-extraction of bioactive components from chitin-rich plants or microorganisms.