EFFECT OF PH ON PRODUCTION OF XYLANASE BY TRICHODERMA-REESEI ON XYLAN-BASED AND CELLULOSE-BASED MEDIA

Trichoderma reesei VTT-D-86271 (Rut C-30) was cultivated on media base d on cellulose and xylan as the main carbon source in fermenters with different pH minimum controls. Production of xylanase was favoured by a rather high pH minimum control between 6.0 and 7.0 on both cellulose - and xylan-based media. Although xylanase was produced efficiently on cellulose as well as on xylan as the carbon source, significant produ ction of cellulase was observed only on the cellulose-based medium and best production was at lower pH (4.0 minimum). Production of xylanase at pH 7.0 was shown to be dependent on the nature of the xylan in the cultivation medium but was independent of other organic components. B est production of xylanase was observed on insoluble, unsubstituted be ech xylan at pH 7.0. Similar results were obtained in laboratory and p ilot (200-1) fermenters. Downstream processing of the xylanase-rich, l ow-cellulase culture filtrate presented no technical problems despite apparent autolysis of the fungus at the high pH. Enzyme produced in th e 200-1 pilot fermenter was shown to be suitable for use in enzyme-aid ed bleaching of kraft pulp. Due to the high xylanase/cellulase ratio o f enzyme activities in the culture filtrate, pretreatment for removal of cellulase activity prior to pulp bleaching was unnecessary.