Studies On The Screening Of Agar Degradation Strains And Agarase Immobilization

Agar, mainly compose of agarose and agaropectin, is one of the most widely used marine polysaccharides. The agaro-oligosaccharide which was degraded from agarose by agarase, has many biological activities such as antioxidant and anti-inflammatory activity, is one kind of potential oligosaccharide. In this paper, one agar degradation strain was screened, and its agarase producing conditions,free and immobilized agarase properties were also studied.The main results were as follows:( 1) Using lugol iodine staining, a strain was screened from Gelidium amansii and Gracilaria verrucosa, and its agarase activity was 2.89 U/m L. After 16 S r DNA sequence alignment, the strain was belong to Pseudoalteromonas, and named as Pseudoalteromonas sp.Z.(2)The optimal conditions of agarase production and free agarase properties were studied:when carbon source was agar, the nitrogen source was peptone, the inoculum size was 1 %,the agar concentration was 0.2%, the rotational speed was 140 r/min,agarase activity can reached the highest level. Its optimum temperature was 35 ℃ and stabilize within 30 to 40℃in p H 8.0. And some ions such as Fe2+, Mg2+, Ca2+, Mn2+, Zn2+, K+, NH4+and SDS can inhibited agarase enzymatic reaction in different degrees.( 3) The immobilization conditions for immobilized agarase were also studied: when sodium alginate was 40 g/L, the immobilized agarase activity was 1.39U/m L; the ratio of agarase to sodium alginate solution was 1:3, the immobilized agarase activity was 1.57U/m L;immobilized 2 h, the immobilized agarase activity was 2.09U/m L; Ca Cl2 concentration was4%, the immobilized agarase activity was 1.92U/m L; hardening for 1 h, the immobilized agarase activity was 1.88U/m L; p H was 7.5, the immobilized agarase activity was 1.95U/m L.Based on single factor experiment and orthogonal experiment, the optimal combination for immobilization condition was: sodium alginate concentration was 40 g/L, Ca Cl2 concentration was 4%, and the ratio of agarase to sodium alginate solution was 1:3. Under this condition,the agarase activity was 2.1U/m L, better than that on single factor experiment.(4)The enzymatic properties of immobilized agarase were also studied: the optimum reaction temperature was 40 ℃ and stabilize within 35 to 50 ℃, 5℃ higher than that in freeagarase, its optimum p H was 8.5, stabilize within the scope of p H 7.0 to 9.0. And its operating stability was not very well; the agarase activity fell to 0.58 U/m L from 1.92 U/m L after 4times reused.