W e have observed that Taka-amylase (TAA) activity disappeared in submerged culture of Aspergillus oryzae at the later-stage of cultivation. This disappearance was revealed to be caused by adsorption of TAA on fungal mycelia. W e have also showed that cell wall of A. oryzae prepared from mycelia at the later-stage of cultivation has an adsorption ability for TAA. This suggested that a certain cell wall factor(s) can adsorb TAA, resulting in the disappearance of TAA in liquid medium during cultivation. To identify the adsorption factor(s) in fungal cell wall, we carried out stepwise fractionation of cell wall prepared from mycelia at the later cultivation stage by alkali extraction and cell wall lytic enzymes. The alkali-insoluble fraction of cell wall, CW 4, showed high adsorption ability for TAA, but digestion of CW 4 with chitinase resulted in a significant decrease in the adsorption ability. These results indicated that the adsorption factor for TAA is chitin, which is one of major polysaccharides in fungal cell wall. However, the cell wall prepared from mycelia at the earlier cultivation stage barely adsorbed TAA, although it contained equivalent amount of chitin to that of later-stage mycelia. Taken together, it is suggested that there exists unidentified factor(s) that could prevent from adsorption of TAA onto the cell wall at the earlier-stage of cultivation and the factor(s) would be removed from or decreased in the cell wall with longer cultivation periods.
Full conference title:
7th International Aspergillus Meeting
- Asperfest 7 (2010)