Production of thermotolerant and alkalotolerant cellulolytic enzymes by isolated Nocardiopsis sp KNU
Production of thermotolerant and alkalotolerant cellulolytic enzymes by isolated Nocardiopsis sp KNU
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DOI：
10.1007/s10532-010-9450-0
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发表时间：
2011-09-01
期刊：
影响因子：
3.6
通讯作者：
Oh, Sang Eun
中科院分区：
文献类型：
--
作者：
Saratale, Ganesh D.;Oh, Sang Eun
从KNU大学校园的森林土壤中分离到一株新的纤维素分解细菌。经16 S rRNA序列比对和形态学观察，鉴定为拟诺卡氏菌（Nocardiopsis sp. KNU）。该菌株能利用羧甲基纤维素（CMC）、微晶纤维素、木聚糖、纤维二糖、滤纸和稻草等多种纤维素底物，产生大量的耐热内切葡聚糖酶、外切葡聚糖酶、木聚糖酶和葡糖淀粉酶。确定了最佳培养条件（Dubos培养基、37 ℃、pH6.5和静态条件）。该菌株产生的纤维素分解酶和半纤维素分解酶的活性主要存在于胞外，并且酶的产生依赖于用于生长的纤维素底物。系统研究了理化条件和金属添加剂对纤维素酶产酶的影响。拟诺卡氏菌KNU产纤维素酶的最适温度为40 ℃，最适pH为5.0。这些纤维素酶还具有高的耐热性，如通过在80 ℃和pH 5.0下保持55-70%的活性所证明的，以及通过在pH 10和40 ℃下1小时后保持> 55%的活性所证明的耐高温性。利用酿酒酵母（Saccharomyces cerevisiae，KCTC-7296）对稻草水解液进行发酵转化，乙醇产率达到理论值的64%。
A novel cellulolytic bacterium was isolated from the forest soil of KNU University campus. Through 16S rRNA sequence matching and morphological observation it was identified as Nocardiopsis sp. KNU. This strain can utilize a broad range of cellulosic substrates including: carboxymethyl cellulose (CMC), avicel, xylan, cellobiose, filter paper and rice straw by producing a large amount of thermoalkalotolerant endoglucanase, exoglucanase, xylanase and glucoamylase. Optimal culture conditions (Dubos medium, 37A degrees C, pH 6.5 and static condition) for the maximal production of the cellulolytic enzymes were determined. The activity of cellulolytic and hemicelluloytic enzymes produced by this strain was mainly present extracellularly and the enzyme production was dependent on the cellulosic substrates used for the growth. Effect of physicochemical conditions and metal additives on the cellulolytic enzymes production were systematically investigated. The cellulases produced by Nocardiopsis sp. KNU have an optimal temperature of 40A degrees C and pH of 5.0. These cellulases also have high thermotolerance as evidenced by retaining 55-70% activity at 80A degrees C and pH of 5.0 and alkalotolerance by retaining > 55% of the activity at pH 10 and 40A degrees C after 1 h. The efficiency of fermentative conversion of the hydrolyzed rice straw by Saccharomyces cerevisiae (KCTC-7296) resulted in 64% of theoretical ethanol yield.