Dendryphiella arenaria TM94 is an obligate marine fungus. Fucoidanase expressed by TM94 by solid state fermentation was purified. The fermented solid medium was extracted with citric acid buffer, and the extracts were precipitated by acetone and separated on Sephadex G-100 chromatography. The specific fucoidanase activity of purified enzyme was 27-fold than that of the crude enzyme. The recovery of the enzyme was 17.69%. SDS-PAGE was used to identify the purity and the molecular weight of the fucoidanase. A single band appeared on SDS-PAGE gel which suggested that relatively pure fucoidanase has been obtained. The molecular weight of fucoidanase is 180 kDa and the isoelectric point was about pH 4.4. The purified fucoidanase appeared to have the maximum enzymatic activity at pH 6.0. K M and the maximum velocity of the enzyme was 6.56 mg·mL −1 and 6.55 mg·mL −1 ·min −1 by using fucoidan from Fucus vesiculosus as substrate. The enzyme may be a type of endo-fucoidanase which could hydrolyze high molecular weight fucoidan to low molecular weight fucoidan rather than to fucose.
Bacillus subtilis JA antagonized the growth of Gibberella zeae. In order to reduce growth of this fungi pathogen to a greater extent, low-energy ion beam implantation was applied in mutant breeding. We studied the effects of different energies and different doses of nitrogen ion implantation. The mutant strain designated as JA026 was obtained showing higher inhibition activity in the screening plate. Its inhibition zone against indicator organism increased by 14.3% compared to the original strain. The electrospray ionization mass spectrometry (ESI/MS) analysis indicated that the antifungal lipopeptides produced by the mutant were identical to those produced by the wild-type strain. The mutant strain exhibited favorable properties including the high yield of antifungal lipopeptides production and faster growth over the parent strain, which suggested that this strain would be a promising biocontrol candidate in agriculture.
With ion implantation (N+, energy 10 keV and dosage 1.56 x 1015 N+ cmP2), a high xylanase-producing strain Aspergillus niger N212 was selected. Based on an orthogonal experiment, an optimal fermentation condition was designed for this high-yield strain. The suitable medium was composed of 8% corncob; 1.0% wheat bran; 0.1% TWEEN20; 0.5% (NH4)2S04; 0,5%NaN03; 0.5%FeS04, 7.5 x MnS04.Hz0, 2.5 x ZnSO4, 2.0 x CoC12, 3.0 x At present, under our experiment condition, xylanase activity of Aspergillus niger N212 reached a level of 600 IU/ml, almost increased by 100% in xylanase production and the time of yielding xylanase was largely reduced to 12 h at 28 "C.
ANNALS NEW YORK ACADEMY OF SCIENCES 216 FIGURE 1. Time course of xylanase production from Aspergillus niger A3 using liquid fermentation: (᭡) dry cell weight, () xylanase activity, (᭢) pH, (b) residual reducing sugars.
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