Liquid Fermentation And Immobilization For Aspergillus Oryzae Aminoacylase

Tryptophan is mainly used in the fields of medicine and foodstuff. In the meantime, tryptophan is the third largest feed additive behind methionine and lysine. But the overprice has limited it's use in the field of feed. In recent years, it is widely concerned at home and abroad because of the lower price of the preparation for L-tryptophan through chemical synthesis and enzymatic resolution.In this paper, the fermentation for Aspergillus oryzea aminoacylase and the preparation for L-tryptophan by using immobilized Aspergillus oryzea mycelia were studied. The main conclusions were as follows.Through the analyse of response surface methodology, the optimal media was attained, which consisted of such materials as wheat bran 2.8%, peptone 1.3%, corn steep liquor 0.7%, MgSO4 0.1%, KH2PO40.2% and Tween-80 0.05%. The optimal media allowed the aminoacylase production to reach 130.4U/g wet mycelia which was 180% higher that before optimization. Through the temperature-changing fermentation, the aminoacylase production increased by 13%.The growth of mycelia and the production of aminoacylase were studied in a 15L air-lift-loop fermentor. The growth rate was faster than that in a flask culture. The peak time of enzymatic production was six hours shorter than that in a flask culture, while the highest enzymatic production slightly decreased.Aspergillus oryzea mycelia were immobilized in different ways. The residual enzymatic activity was 28.7% by glutaraldehyde immobilization, higher than the others. Through the orthogonal experiment, the optimal conditions of immobilization was as follows: glutaraldehyde concentration at 0.5%, immobilized time at 2h and the ratio of volume to mycelia at 1 OmL immobilized liquid/g wet mycelia. In the optimal condition, the highest residual enzymatic activity was 31.4%.The properties of immobilized mycelia were studied. The results indicated that the immobilized mycelia had higher stability against pH and temperature than the freemycelia.The resolution of N-acryl-DL-Tryptophan was investigated in batch. The half life of immobilized mycelia was estimated to be 26.7 days, L-tryptophan in the resolution solution was attained by means of concentration, crystallization, decolour and so on. The chemical purification was 98.9% and optical purification was 98.5%.