| Abstrakt: |
The immobilization in polyacrylamide gel (PAAG) of the Aspergillus nigermycelium, which has the activity of hydroxylating indolyl-3-acetic acid (IAA) at 4-, 5-, and 6-positions of the indole nucleus, was studied. To preserve the hydroxylating activity, the immobilization should be performed at 5°C–10°C for 5–10 min. The hydroxylating activity of the A. nigermycelium entrapped in PAAG attained 70%–80% of that of free cells. The IAA transformation in the presence of sodium desoxycholate, polyethylene-glycol-400 (PEG-400), Span-60 or preincubation of granules entrapping mycelia in the presence of Tween-80 or PEG-400 not only double the hydroxylation rate but stabilize the activity as well. Gels entrapping mycelia may be used five or six times without altering activity. Incubation of gels with mycelium in the nutrient medium also increases and stabilizes the hydroxylating activity. In aerated columns, it is possible to obtain continuous hydroxylation of IAA, at a concentration of 0.5 g/l, by the immobilized mycelium of A. niger. The yield of hydroxy derivatives reached 70%, the activity remaining unaltered during 15 days' operation of the column. |
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