Sunday, August 10, 2008
P23

High-level secretory production and characterization of Bacillus licheniformis endo-1,4-beta-glucanase Cel9A in Bacillus subtilis WB800

Wai Mui Tjia and Sui-lam Wong. Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada

We report the production and characterization of a B. licheniformis endo-1,4-beta-glucanase, Cel9A, from B. subtilis.  As an ideal cellulase for bioethanol production, it has to be produced in high yield at low cost.  Another desirable feature is its ability to retain high activities in a wide temperature range.  High activity at 30°C allows the two key processes, cellulose hydrolysis and yeast fermentation, to be operated simultaneously that lowers the operating cost.  Alternatively, high activity at high temperature offers flexibility to have separate processes for efficient enzymatic cellulose hydrolysis at high temperature and yeast fermentation at lower temperature.  B. licheniformis is an attractive source for ideal cellulases because it efficiently hydrolyses cellulose and grows at a wide range of temperature.  Furthermore, B. licheniformis enzymes are likely to be produced well using the engineered B. subtilis expression-secretion system.

The secretory production yield of Cel9A is 46.76 mg/liter. Cel9A binds strongly to avicel and acid-swollen cellulose, but not to chitin beads or xylan. It is active between pH 6-9 and 20-80°C, optimally at pH 7-8 and 50°C. It exhibits high activities of 250.14 IU/mg to carboxymethylcellulose, 4.64 IU/mg to acid-swollen cellulose and 2.05 IU/mg to avicel at 50°C. The Km and Vmax of Cel9A is 33 mg/ml and 433.6 µmol/min/mg.  It retains 60% activities at 30°C.  Results of thin-layer chromatography showed that Cel9A hydrolyzes cellulose randomly and is more active towards cellopentaose. Due to its high production yield and desirable features, Cel9A produced can potentially be a key cellulase for industrial applications.


See more of Poster Session 1
See more of Posters

See more of The Annual Meeting and Exhibition 2008 (August 10 - 14, 2008)