การผลิตไซแลนเนสจาก Aureobasidium pullulans และผลต่อเยื่อกระดาษยูคาลิปตัส / ธาริณี พังจุนันท์ = Xylanase production from Aureobasidium pullulans and its effect on the eucalyptus paper pulp / Tarinee Pangjunan|
Two strains of Aureobasidium pullulans, ATCC and NRRL were cultivated in submerge culture containing xylose as the sole caebon source. These two strains had highest xylanase activity (ATCC 22.47 IU and NRRL 23.99 IU) at pH 5, Temperature 30º C. The optimal condition culturing A. pullulans along with the agricultural carbon source include for rice husk, rice straw, refined rice bran or unprocessed rice bran was used instead of 1% xylose. The ATCC strain had highest xylanase activity in refined rice bran (5.79 IU) while the NRRL strain had highest xylanase activity in rice straw (3.68 IU). In the varied concentration of carbon sources, the ATCC strain had highest xylanase activity when refined rice bran 3% was used (6.97 IU), and rice straw 4% gave the highest xylanase activity in NRRL strain (7.18 IU). After that, the enzyme was purified by ammonium sulfate precipitation at 30-50% concentration; the enzyme activity increased 5.17 and 4.86 fold in ATCC and NRRL strains respectively. After the enzyme was used to bleach eucalyptus paper pulp, the Kappa number of pulp decreased when increasing the enzyme dosage. Xylanase 50 IU per g OD from ATCC strain gave lowest Kappa number at 8.3382. The brightness of pulp was slightly increase, compared to the unbleached pulp. Xylanase 50 IU per g OD from ATCC strain gave highest brightness as 46.17%. The filtrate from enzyme bleaching was measured its absorbency at u v region. Using low level of ATCC’s xylanase (5 and 25 IU per g OD) gave the absorbance peaks similar to the standard xylanase treatment at 5 IU per g OD. When using xylanase from ATCC strain 50 IU per g OD, NRRL strain at 5, 25 and 50 IU per g OD and standard xylanase treatment at 25 IU per g OD did not show the UV absorbance peaks.
