Identification and characterization of a marine-derived chitinolytic fungus, Acremonium sp. YS2-2.

Chitin is the most abundant biopolymer in marine environments. To facilitate its utilization, our laboratory screened marine-derived fungal strains for chitinolytic activity. One chitinolytic strain isolated from seawater, designated YS2-2, was identified as Acremonium species based on morphological and phylogenetic analyses. Acremonium species are cosmopolitan fungi commonly isolated from both terrestrial and marine environments, but their chitinolytic activity is largely unknown. The extracellular crude enzyme of YS2-2 exhibited optimum chitinolytic activity at pH 6.0-7.6, 23-45°C, and 1.5% (w/v) NaCl. Degenerate PCR revealed the partial cDNA sequence of a putative chitinase gene, chiA, in YS2-2. The expression of chiA was dramatically induced in response to 1% (w/v) colloidal chitin compared to levels under starvation, chitin powder, and glucose conditions. Moreover, the chiA transcript levels were positively correlated with chitinolytic activities under various colloidal chitin concentrations, suggesting that ChiA mediates chitinolytic activity in this strain. Our results provide a basis for additional studies of marinederived chitinolytic fungi aimed at improving industrial applications.