Kamble Rajashri D, Jadhav Anandrao R
Department of Biotechnology Engineering, Tatyasaheb Kore Institute of Engineering and Technology, Warananagar, Kolhapur, Maharashtra 416113, India.
Department of Microbiology, KRP Kanya Mahavidyalaya, Islampur, Sangli, Maharashtra 415414, India.
ISRN Biotechnol. 2012 Jun 4;2013:872325. doi: 10.5402/2013/872325. eCollection 2013.
The most promising application of xylanases (E.C. 3.2.1.8) is in the prebleaching of kraft pulp. The present paper reports bleaching effects of a thermoalkali stable xylanase from Cellulosimicrobium sp. MTCC 10645. The bacterium produced thermo-alkali stable xylanase in a basal medium supplemented with wheat bran (1% w/v), which was optimally active at pH 7.0 and 50°C. The xylanase was stable at temperature 50°C for 1 h and retained up to 86% of the activity. The xylanase was stable in a broad pH range of 6.0-11.0 for 1 h at 50°C. Metal ions Ca(+2), Hg(+2), and Pb(+2) were inhibitory for xylanase retaining 72.3%, 35.07% and 36.7% relative activity at 10 mM concentration, whereas Fe(+2), Cu(+2), Mn(+2), Na(+2), Co(+2), and Zn(+2) were inducers at concentrations of 5 mM and 10 mM. The enzyme exhibited greater binding affinity exclusively for xylans but not for avicel, CMC, cellobiose, starch, or p-nitrophenyl xylopyranoside. Parachloromercuric benzoate and iodoacetamide were found stimulatory, while potassium permanganate, cysteine, and cystine markedly reduced the activity. The xylanase dose of 2.0 U/g dry weight pulp of 10% consistency gave optimum bleach boosting of kraft pulp at pH 8.0 and temperature 50°C for 5 h reaction time.
木聚糖酶（E.C. 3.2.1.8）最有前景的应用是在硫酸盐浆的预漂白中。本文报道了来自纤维微菌属菌株MTCC 10645的一种热碱稳定木聚糖酶的漂白效果。该细菌在添加了麦麸（1% w/v）的基础培养基中产生热碱稳定木聚糖酶，其在pH 7.0和50°C时活性最佳。该木聚糖酶在50°C下1小时内稳定，保留了高达86%的活性。在50°C下，该木聚糖酶在6.0 - 11.0的宽pH范围内1小时内稳定。金属离子Ca(+2)、Hg(+2)和Pb(+2)对木聚糖酶有抑制作用，在10 mM浓度下相对活性分别保留72.3%、35.07%和36.7%，而Fe(+2)、Cu(+2)、Mn(+2)、Na(+2)、Co(+2)和Zn(+2)在5 mM和10 mM浓度下是诱导剂。该酶仅对木聚糖表现出更高的结合亲和力，但对微晶纤维素、羧甲基纤维素、纤维二糖、淀粉或对硝基苯基木糖苷没有结合亲和力。对氯汞苯甲酸和碘乙酰胺具有刺激作用，而高锰酸钾、半胱氨酸和胱氨酸显著降低了活性。在pH 8.0、温度50°C、反应时间5小时的条件下，10%浓度的纸浆中木聚糖酶剂量为2.0 U/g干重时，对硫酸盐浆的漂白促进效果最佳。
