The Screening Of Alginate Lyase Strains And Studies On Its Enzymatic Characterizations

Alginate lyases, one kind of complex copolymers of L-guluronate and its C5 epimer Dmannuronates, can catalyze the degradation of alginate with β-elimination mechanism and yield alginate oligosaccharides. Alginate oligosaccharide had many kinds of biological activities, such as promoting growth, enhancing resistance and bacteriostasis, has attracted more and more people’s attention. In this paper, one alginate lyase strain was screened and its growth optimization, alginate lyase immobilization and the enzymatic characterization of immobilized and free alginate lyase were also studied. The main results were as follows:1. The strains which can produce alginate lyase were isolated from rotting Laminaria japonica. After enrichment culture and primary screening, 14 strains were screened and one higher alginate lyase producing strain was determined after secondary screening. It was identified Pseudoalteromonas and named as Pseudoalteromonas sp.L1.2. The medium composition and fermentation conditions of Pseudoalteromonas sp.L1 were optimized. Pseudoalteromonas sp.L1 could grow well in the medium contained yeast3g/L, alginate 6g/L, Na Cl 30g/L in p H 7.0. The optimum fermentation conditions of Pseudoalteromonas sp.L1 were as follow: liquid volume 30 m L in 250 m L flask, rotating speed160r/min, inoculation quantity 1%, cultured in 30℃for 12 h.3. Alginate lyases immobilized with gelatin and cross linked with glutaraldehyde were studied and its immobilization conditions and enzymatic properties were also determined.The optimum conditions of immobilization were: gelatin 15%, glutaraldehyde volume 0.5%,the ratio of crude enzyme to gelatin was 1:3, cross-linked 2h and immobilized for 4h. Under this condition, the activity of immobilized alginate lyase reached a maximum level of18.11U/m L, the recovery rate of immobilized enzyme was 88.86%. The optimum temperatures of immobilized and free enzyme were 55℃ and 45℃; and the optimum p H was 4 and 5 respectively. Both p H and temperature stability of the immobilized alginate lyases were significantly increased.