Xylanase Subject

Xylanase production by B. circulans was induced by a variety of carbon sources, and among the tested substrates, maltose was the best inducer. These data suggest two modes of enzyme expression one gene that codes for a constitutive xylanase and another gene that codes for a xylanase subject to induction or a single gene that constitutively expresses basal levels of the enzyme and that also is susceptible to induction by specific sugars. 

Selective Production of Xylanases by Cellulolytic Microorganisms. Until recently there was little information on common or separate genetic control of cellulase and xylanase synthesis in microorganisms (60). Studies on this subject were complicated by the fact that numerous microbial ceUulases and xylanases are non-specific with respect to cellulose and xylan as substrates. As could be expected from a comparison of both polysaccharide structures, non-specificity is more frequently observed with cel-lulases, because their substrate binding sites can easily accommodate substrate using an unsubstituted p-(l 4)-linked chain of D-xylopyranosyl units. 

Xylanase II was subjected to cation exchange chromatography with a 20-mm i.d., 700-mm long CM-Trisacryl column eluted with 0.8 mL/min of 0.025M sodium acetate buffer at pH 4.5, with a 0-0.2M sodium chloride gradient. Only one protein peak eluted from the column it contained all the Xylanase n activity. This material appeared... 

Effect of Temperature and pH on Activity and Stability. When Xylanase II was subjected to the standard assay at pH 5 but at several different temperatures, the highest activity was found after incubation for 30 min at 60°C. From 21 C to 45 C the energy of activation from a linear plot of In (activity) vs. T was 41.6 2.1 kJ/mol, where the range is the standard deviation. When the standard assay was conducted at various pHs and 50°C, the highest activity was at pH 6.05. Activities half the maximum were found at pHs 4.4 and 8.0. 

A comprehensive review on D-xylanases and their degradation of D-xylans was written by Sorensen5 in 1957, and since then, brief reviews of the same subject have been written in English by Timell6 and in Japanese by Fukui7 (1961) and Sasaki8 (1971). Work on D-xylanases from 1957 onwards will, therefore, be discussed in detail in this article. 

We had two patients with allergic patch-test reactions to cellulase and xylanese (Tarvainen et al. 1991b, Table 3). Cellulase and xylanase were tested in a dilution series (3.3%> i%> 0.33%) in petrolatum and aqua. As a control, 20 non-exposed subjects (10 atopies) were patch tested with a concentration of 3.3% w/v in petrolatum, with negative results. Currently, scanty data are available on how to patch test with industrial enzymes. Optimal patch test concentrations need to be established for each enzyme, and controls are necessary. 

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