Cold-active and NaCl-tolerant exo-inulinase from a cold-adapted Arthrobacter sp. MN8 and its potential for use in the production of fructose at low temperatures

Publication date: Available online 27 September 2014 Source:Journal of Bioscience and Bioengineering Author(s): Junpei Zhou , Qian Lu , Mozhen Peng , Rui Zhang , Minghe Mo , Xianghua Tang , Junjun Li , Bo Xu , Junmei Ding , Zunxi Huang An exo-inulinase gene was cloned from Arthrobacter sp. MN8, a cold-adapted bacterium isolated from lead–zinc-rich soil. The gene was expressed in Escherichia coli BL21(DE3). The resultant 505-residue polypeptide (InuAMN8) showed the highest identity (81.1%) with the putative levanase from Arthrobacter phenanthrenivorans Sphe3 (ADX73279) and shared 57.8% identity with the exo-inulinase from Bacillus sp. snu-7 (AAK00768). The purified recombinant InuAMN8 (rInuAMN8) showed an apparently optimal activity at 35°C, and 75.3%, 39.4%, and 15.8% of its maximum activity at 20°C, 10°C, and 0°C, respectively. After pre-incubation for 60 min at 50°C and 55°C, the rInuAMN8 exhibited 69.8% and 17.7% of its initial activity, respectively. The apparent K m values of rInuAMN8 towards inulin were 2.8, 1.5, 1.2, 5.3, and 8.2 mM at 0°C, 10°C, 20°C, 30°C, and 35°C, respectively. Inulin and Jerusalem artichoke tubers were effectively hydrolyzed to release fructose by rInuAMN8 at 0°C, 10°C, and 35°C. Compared with its hyperthermophilic and thermophilic counterparts, the exo-inulinase had less aromatic amino acid F and more hydrophobic amino acid A. In addition, the purified rInuAMN8 retained 127.9%–88.4% inulinase activity at 3.5%–1...
Source: Journal of Bioscience and Bioengineering - Category: Biomedical Science Source Type: research