Raj Abhay, Kumar Sharad, Singh Sudheer Kumar, Kumar Mahadeo
Environmental Microbiology Section, CSIR-Indian Institute of Toxicology Research, M.G. Marg, Post Box No. 80, Lucknow, Uttar Pradesh 226 001, India.
Microbiology Division, CSIR-Central Drug Research Institute, Jankipuram Extension Sector 10, Sitapur Road, Lucknow, Uttar Pradesh 226 003, India.
ScientificWorldJournal. 2013 Nov 20;2013:386769. doi: 10.1155/2013/386769. eCollection 2013.
Providencia sp. strain X1 showing the highest xylanase activity among six bacterial isolates was isolated from saw-dust decomposing site. Strain X1 produced cellulase-free extracellular xylanase, which was higher in wheat bran medium than in xylan medium, when cultivated at pH 8.0 and 35°C. Zymogram analysis of crude preparation of enzymes obtained while growing on wheat bran and birchwood xylan revealed the presence of seven and two distinct xylanases with estimated molecular weight of 33; 35; 40; 48; 60; 75; and 95 kDa and 33 and 44 kDa, respectively. The crude xylanases were produced on wheat bran medium and showed optimum activity at pH 9.0 and 60°C. The thermotolerance studies showed activity retention of 100% and 85% at 40°C and 60°C after 30 min preincubation at pH 9.0. It was tolerant to lignin, ferulic acid, syringic acid, and guaiacol and retained 90% activity after ethanol treatment. The enzyme preparation was also tolerant to methanol and acetone and showed good activity retention in the presence of metal ions such as Fe2+, Mg2+, Zn2+, and Ca2+. The crude enzyme preparation was classified as endoxylanase based on the product pattern of xylan hydrolysis. Pretreatment of kraft pulp with crude xylanases for 3 h at 60°C led to a decrease in kappa number by 28.5%. The properties of present xylanases make them potentially useful for industrial applications.
从锯末分解位点分离出的普罗威登斯菌属菌株X1在六种细菌分离物中显示出最高的木聚糖酶活性。菌株X1产生无纤维素酶的细胞外木聚糖酶，在pH 8.0和35°C培养时，在麦麸培养基中产生的木聚糖酶比在木聚糖培养基中更高。对在麦麸和桦木木聚糖上生长时获得的酶粗制品进行酶谱分析，发现分别存在七种和两种不同的木聚糖酶，估计分子量分别为33、35、40、48、60、75和95 kDa以及33和44 kDa。粗木聚糖酶在麦麸培养基上产生，在pH 9.0和60°C时表现出最佳活性。耐热性研究表明，在pH 9.0预孵育30分钟后，在40°C和60°C下活性保留率分别为100%和85%。它对木质素、阿魏酸、丁香酸和愈创木酚具有耐受性，乙醇处理后保留90%的活性。酶制剂对甲醇和丙酮也具有耐受性，并且在存在Fe2+、Mg2+、Zn2+和Ca2+等金属离子时表现出良好的活性保留。根据木聚糖水解的产物模式，粗酶制剂被归类为内切木聚糖酶。用粗木聚糖酶在60°C下对硫酸盐浆预处理3小时，导致卡伯值降低28.5%。目前木聚糖酶的特性使其在工业应用中具有潜在的用途。
