An extracellular multiple form of endoxylanase was isolated from the xylanolytic complex of Aspergillus niger B03. Th e enzyme was purifi ed to a homogenous form using ultrafi ltration, anion exchange chromatography, and gel fi ltration. It was a nonglycosylated protein with a molecular weight of 20,000 Da as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and 21,000 Da as determined by gel fi ltration. Th e optimal pH for the enzyme action was 5.0 and the optimal temperature was 55 °C. Endoxylanase stability was signifi cantly improved in the presence of glycerol and sorbitol. Th e enzyme activity was activated by Mn 2+ and Co 2+ , and it was inhibited by Ag + , Cu 2+ , Fe 3+ , Fe 2+ , and Pb 2+ . Th e substrate specifi city and the product profi le of the enzyme suggested that it was an endoxylanase. Th e enzyme showed a synergism with another endoxylanase from Aspergillus niger B03 in xylan hydrolysis.
From a rabbit lymphoid tissue, twice immunized with a Salmonella ch. suis vaccine, was obtained a dialysable leucocyte extract (DLE) (m. w. 10,000Da; protein content 1.14 mg/ml; content of ribose 2.7 mg/ml; A260/A280 ratio 2.17 and pH 6.8). By gel filtration on Sephadex G-25, six peaks were obtained and activity was found in peak IV. The activity of the extract was determined by a dermo-application test (DAT) on 10 cows. The protective effect was tested by a challenge with Salmonella ch. suis and Salmonella dublin pathogen strains on white mice intraperitoneally treated with DLE. The DAT proved to be positive in 8 of the 10 cows. When applied on white mice, it induced a high specific protective effect against Salmonella ch. suis (70%), but not against Salmonella dublin infection.
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