Silveira F Q, Ximenes F A, Cacais A O, Milagres A M, Medeiros C L, Puls J, Filho E X
Laboratório de Enzimologia, Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF, Brasil.
Braz J Med Biol Res. 1999 Aug;32(8):947-52. doi: 10.1590/s0100-879x1999000800003.
Xylanase activity was isolated from crude extracts of Trichoderma harzianum strains C and 4 grown at 28 degree C in a solid medium containing wheat bran as the carbon source. Enzyme activity was demonstrable in the permeate after ultrafiltration of the crude extracts using an Amicon system. The hydrolysis patterns of different xylans and paper pulps by xylanase activity ranged from xylose, xylobiose and xylotriose to higher xylooligosaccharides. A purified ss-xylosidase from the Trichoderma harzianum strain released xylose, xylobiose and xylotriose from seaweed, deacetylated, oat spelt and birchwood xylans. The purified enzyme was not active against acetylated xylan and catalyzed the hydrolysis of xylooligosaccharides, including xylotriose, xylotetraose and xylopentaose. However, the enzyme was not able to degrade xylohexaose. Xylanase pretreatment was effective for hardwood kraft pulp bleaching. Hardwood kraft pulp bleached in the XEOP sequence had its kappa number reduced from 13.2 to 8.9 and a viscosity of 20. 45 cp. The efficiency of delignification was 33%.
木聚糖酶活性是从哈茨木霉C菌株和4菌株的粗提物中分离得到的，这些菌株在以麦麸作为碳源的固体培养基中于28℃培养。使用Amicon系统对粗提物进行超滤后，在渗透物中可检测到酶活性。木聚糖酶活性对不同木聚糖和纸浆的水解模式范围从木糖、木二糖和木三糖到更高的低聚木糖。从哈茨木霉菌株中纯化得到的一种β-木糖苷酶可从海藻、脱乙酰化、燕麦麸和桦木木聚糖中释放出木糖、木二糖和木三糖。纯化后的酶对乙酰化木聚糖无活性，但可催化包括木三糖、木四糖和木五糖在内的低聚木糖的水解。然而，该酶无法降解木六糖。木聚糖酶预处理对阔叶木硫酸盐浆漂白有效。采用XEOP流程漂白的阔叶木硫酸盐浆，其卡伯值从13.2降至8.9，粘度为20.45厘泊。脱木素效率为33%。
