Identification of potential cell wall component that allows Taka-amylase A adsorption in submerged cultures of <Emphasis Type="Italic">Aspergillus oryzae</Emphasis> |
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Authors: | Hiroki Sato Yoshiyuki Toyoshima Takahiro Shintani Katsuya Gomi |
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Institution: | (1) Laboratory of Bioindustrial Genomics, Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai 981-8555, Japan;(2) Present address: Yamasa Shoyu Co. Ltd., Choshi, Chiba, Japan; |
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Abstract: | We observed that α-amylase (Taka-amylase A; TAA) activity in the culture broth disappeared in the later stage of submerged
cultivation of Aspergillus oryzae. This disappearance was caused by adsorption of TAA onto the cell wall of A. oryzae and not due to protein degradation by extracellular proteolytic enzymes. To determine the cell wall component(s) that allows
TAA adsorption efficiently, the cell wall was fractionated by stepwise alkali treatment and enzymatic digestion. Consequently,
alkali-insoluble cell wall fractions exhibited high levels of TAA adsorption. In addition, this adsorption capacity was significantly
enhanced by treatment of the alkali-insoluble fraction with β-glucanase, which resulted in the concomitant increase in the
amount of chitin in the resulting fraction. In contrast, the adsorption capacity was diminished by treating the cell wall
fraction with chitinase. These results suggest that the major component that allows TAA adsorption is chitin. However, both
the mycelium and the cell wall demonstrated the inability to allow TAA adsorption in the early stage of cultivation, despite
chitin content in the cell wall being identical in both early and late stages of cultivation. These results suggest the existence
of unidentified factor(s) that could prevent the adsorption of TAA onto the cell wall. Such factor(s) is most likely removed
or diminished from the cell wall following longer cultivation periods. |
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