Preparation Of L-arabinose From Gum Arabic Hydrolyzed By Enzyme

An effective enzyme-producing strain which could hydrolyze gum Arabic was isolated from soil samples of Hangzhou, Shijiazhuang and Huangdao. After further purification, strain named ZHB-306 which enzyme activity reached 25.8 U/mL and enzyme fermentation performance stability was obtained. When growing in the plate, the strain could grow into colonise in 2~3 days. Myceliums were white and dense on the early colonies which protruded flocculent. The color of colonise were from white, pale pink, incarnadine to slightly purple; spores were from light brown to black. The strain is very similar to Fusarium morphologically, the species of which need molecular biology identificatio.Mutation breeding was applied to enhance the ability of producing agarase of the strain ZHB-306 by ultraviolet mutation and the activity of enzymes was increased by 185%.The experiments of single factors and orthogonal design were carried out to optimize the culture medium and cultivation conditions. As a result, the optimal medium composition was as follows: gum Arabic 2.5%, corn flour 0.4%, (NH4)2SO4 0.9%, K2HPO4 0.15%, MgSO4?7H2O 0.05%, KCl 0.05%, FeSO4?7H2O 0.001%, H3BO3 0.001%, pH was adjusted to 6.0. The fermentation for enzymes production was carried out in 250-mL Erlenmeyer flasks containing 30 mL of medium with inoculation of 9% (v/v) seeds, incubated at a agitation speed of 200 r/min and 30℃for about 48 h. The enzymes activity reached 231.6 U/mL under the optimum conditions and it was 368% higher than that before the optimization. Fermentation results could be applied to the further study and industrial production of this enzymes, and the development and application of L-arabinose.The HPLC-ELSD detection method of L-arabinose were established after a series of experiments. Different kinds of sugar could be separated on Hypersil NH2 column with the mobil phase of acetonitrile-water (80:20) at a flow rate of 1 mL/min. The condition of Evaporative light scattering detector were set as followings: the temperature of drift tube was 100℃, nitrogen gas was used as carrier with the flow rate of 2.5 L/min. L-Arabinose could be separated from other saccharides. The correlation coefficient of linear regression equation for L-arabinose was 0.9993. The reproducibility was RSD of 2.03%. The average recovery was 98.7%.The enzymatic conditions of degrading gum rabic into L-arabinose by the enzymes were also studied. The results showed that the optimal time, temperature and agitation rate for enzymatic reaction were 90 min, 50℃and 0r/min respectively. The optimal substrate was 0.3% (w/v) gum arabic which pH4.0. Determination of L-arabinose after digested with the best conditions by using HPLC-ELSD method, the concentration was 530.6 mg / L, and thus calculated L-arabinose yield was 59.8%. Therefore, it was essential to do some further researches on enzymological properties of the enzymes.