Jalal Amir, Rashid Naeem, Rasool Nouman, Akhtar Muhammad
School of Biological Sciences, University of the Punjab, Lahore, Pakistan.
J Biosci Bioeng. 2009 Apr;107(4):360-5. doi: 10.1016/j.jbiosc.2008.12.005.
A novel mesophilic strain, R5, was isolated from Osaka, Japan. The growth temperature of the strain ranged from 10 to 40 degrees C with optimal growth at 30 degrees C. Cells of strain R5 were highly motile small rods. The full-length 16S rRNA sequence was 99% homologous to that of Bacillus subtilis strain 168. The optimum pH and NaCl concentration for growth of the strain were 7.0 and 3%, respectively. Based on the biochemical characteristics and 16S rRNA sequences R5 was identified as a strain of B. subtilis. The strain R5 produced protease, cellulase, amylase, lipase/esterase, xylanase and a biosurfactant extracellularly. The gene encoding xylanase was cloned and expressed in Escherichia coli. The gene encoded a protein consisting of 213 amino acids with a relative molecular mass of 23 kDa. The gene product was purified and examined for enzymatic characteristics. The recombinant enzyme exhibited highest activity at temperatures ranging from 40 to 50 degrees C and at pH 6.0. The enzyme activity was enhanced in the presence of metal cations. The V(max) and K(m) values of the recombinant enzyme towards xylan from beech-wood were 5550 nkat/mg and 4.5 mg/mL, respectively.
从日本大阪分离出一种新型嗜温菌株R5。该菌株的生长温度范围为10至40摄氏度，最适生长温度为30摄氏度。菌株R5的细胞是高度运动的小杆状。全长16S rRNA序列与枯草芽孢杆菌菌株168的序列同源性为99%。该菌株生长的最适pH值和NaCl浓度分别为7.0和3%。基于生化特性和16S rRNA序列，R5被鉴定为枯草芽孢杆菌菌株。菌株R5可在细胞外产生蛋白酶、纤维素酶、淀粉酶、脂肪酶/酯酶、木聚糖酶和一种生物表面活性剂。编码木聚糖酶的基因被克隆并在大肠杆菌中表达。该基因编码一种由213个氨基酸组成、相对分子质量为23 kDa的蛋白质。对该基因产物进行纯化并检测其酶学特性。重组酶在40至50摄氏度的温度范围和pH 6.0时表现出最高活性。在金属阳离子存在下酶活性增强。重组酶对山毛榉木木聚糖的V(max)和K(m)值分别为5550 nkat/mg和4.5 mg/mL。
