61A-18 |
Separation of agarose using chitosan as an anion exchanger with orthogonal design |
P. Z. LIAN1, C. M. Lee1, and Q. Zhang2. (1) Dept. of Nutrition and Food Science, University of Rhode Island, Kingston, RI 02881, (2) Dept. Food Engineering, Jimei University, Xiamen, 361021, China Agarose is a neutral polysaccharide consisting of alternating 1,3-linked beta-D-galactopyranose and 1,4-linked 3,6-anhydro-alpha-L-galactopyranos, which is separated from agar by removing charged agaropectin. Agarose has been widely used in the biotech field for fractionation of nucleic acids, serum lipoproteins, viral particles etc. The traditional separation of agarose mainly depends on DEAE-cellulose, a weaker anion exchanger. Chitosan is a natural polysaccharide produced from by-products of crabs and shrimp processing, which has a similar function as DEAE-cellulose in interaction with agaropectin. Our objectives were to prepare chitosan having various deacetyl values (DAc) and screen an optimal condition for the separation of agarose using a L8(41 x 24) orthogonal design. Chitosan samples (~200 mesh) with DAc of 89 and 78 were prepared from fresh crab shell and those with DAc of 81 and 87 from fresh shrimp shell. 25 g of agar (from Gracillaror Porphyra) in 500 mL of distilled water was heated at 98 ± 2°C until dissolved, cooled to 65 or 75°C, and then mixed with 12.5 g of chitosan for 60 or 90 min. After this, the mixture was filtered, gelled, frozen/thawed, washed, dried, and milled. The quality of agarose was evaluated on the analyses of ash, sulfate content, and migration value of polyethanol electrophoresis. The results of orthogonal comprehensive evaluation showed that the factors affecting quality of agarose is in the following order: chitosan species (most influential), agar species, temperature, and time. Agarose of the best quality with less ash and sulfate content can be obtained by using shrimp chitosan with DAc 81%, Porphyra agar at 75°C for 90 min. The results suggest that chitosan can be used as an anion exchanger to separate agarose from agar. Porphyra agar is better than Gracillar agar as the raw material of agarose.
Session 61A, Carbohydrate
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