CELLULASE-FREE XYLANASE BY THERMOMYCES-LANUGINOSUS RT9 - EFFECT OF AGITATION, AERATION, AND MEDIUM COMPONENTS ON PRODUCTION

Several carbohydrates were examined for their ability to induce xylana se in Thermomyces lanuginosus RT9 at 50 degrees C in shake flask cultu res. It was found that xylan or xylan containing substrates, such as c orn cobs, induced maximum and comparable level of xylanase free of cel lulase, while the easily metabolisable sugars (glucose, xylose, and su crose) appeared to repress xylanase synthesis. Low level of constituti ve enzyme was produced as evident from the culture medium without carb on source addition. Initial culture pH significantly influenced both g rowth and xylanase production, exhibiting a maximum at 6.5 on xylan. T he effects of agitation and aeration rates were investigated in a bior eactor. Both influenced significantly the growth, cultivation time and enzymes (xylanase and beta-xylosidase) production. The highest level of xylanase productivity (41630 U l(-1) h(-1)) was achieved at an agit ation of 200 rpm and 1.0 vvm aeration rate. At these conditions, the s pecific xylanase activity in the shake flask could be reproduced. Vari ation of nitrogen components demonstrated that a combination of yeast extract and (NH4)(2)HPO4 supported the best biomass growth, extracellu lar protein and xylanase production. At a C/N ratio of about 6.0 using yeast extract and (NH4)(2)HPO4 containing medium (yeast extract mediu m), a 3-fold higher xylanase production compared with the peptone medi um was achieved in shake flask. However, in bioreactor system, the imp roved specific xylanase activity could not be reproduced due to theolo gical problem under higher biomass formation with accompanying viscosi ty and consequent oxygen transfer efficiency. Hence, the peptone mediu m with xylan (2.0%) is more appropriate to achieve high productivity o f xylanase in bioreactor system.