Production of xylanase by the ruminal anaerobic fungus Neocallimastix frontalis

• Published in: Applied and Environmental Microbiology Vol. 55; no. 4; pp. 1016 - 1022
• Main Authors: Mountfort, D.O, Asher, R.A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.04.1989
• Subjects: Anaerobiosis; Analytical, structural and metabolic biochemistry; Animals; AZUCARES; Biological and medical sciences; BIOSINTESIS; BIOSYNTHESE; Carbohydrate Metabolism; CHAMPIGNON; Chytridiomycota - enzymology; Culture Media; ENZIMAS; ENZYME; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; FUNGI; Glycoside Hydrolases - biosynthesis; Hydrogen-Ion Concentration; Hydrolases; Hydrolysis; MASTIGOPHORA; MICROORGANISME; MICROORGANISMOS; Neocallimastix frontalis; RUMEN; Rumen - microbiology; SUCRES; Temperature; Xylan Endo-1,3-beta-Xylosidase; Xylans - metabolism; Fungi; Substrate; Temperature; Enzymatic activity; Enzyme; Production; Microorganism culture; PH; Environmental factor; Optimization; Xylanolytic enzyme; Thallophyta
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.55.4.1016-1022.1989

Xylanase (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) production was investigated in the ruminal anaerobic fungus Neocallimastix frontalis. The enzyme was released principally into the culture fluid and had pH and temperature optima of 5.5 and 55 degrees C, respectively. In the presence of low concentrations of substrate, the enzyme was stabilized at 50 degrees C. Xylobiose was the principle product of xylanase action, with lesser amounts of longer-chain xylooligosaccharides. No xylose was detected, indicating that xylobiase activity was absent. Activities of xylanase up to 27 U ml-1 (1 U represents 1 micromole of xylose equivalents released min-1) were obtained for cultures grown on xylan (from oat spelt) at 2.5 mg ml-1 in shaken cultures. No growth occurred in unshaken cultures. Xylanase production declined with elevated concentrations of xylan (greater than 2.5 mg ml-1), and this was accompanied by an accumulation of xylose and, to a lesser extent, arabinose. Addition of either pentose to cultures grown on low levels of xylan in which neither sugar accumulated suppressed xylanase production, and in growth studies with paired substrates xylan-xylose, active production of the enzyme occurred during growth on xylan only after xylose had been preferentially utilized. When cellobiose, glucose, and xylose were tested as growth substrates for the production of xylanase (each initially at 2.5 mg ml-1), they were found to be less effective than xylan, and use of xylan from different origins (birch wood or larch wood) as the growth substrate or in the assay system resulted in only marginal differences in enzyme activity. However, elevated production of xylanase occurred during growth on crude hemicellulose (barley straw leaf). The results are discussed in relation to the role of the anaerobic fungi in the ruminal ecosystem, and the possible application of the enzyme in bioconversion processes is also considered