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Abstract：
In the field of biocatalysis, the implementation of sustainable processes such as enzyme immobilization or employment of environmentally friendly solvents, like Deep Eutectic Solvents (DESs) are of paramount importance. In this work, tyrosinase was extracted from fresh mushrooms and used in a carrier-free immobilization towards the preparation of both non-magnetic and magnetic cross-linked enzyme aggregates (CLEAs). The prepared biocatalyst was characterized and the biocatalytic and structural traits of free tyrosinase and tyrosinase magnetic CLEAs (mCLEAs) were evaluated in numerous DES aqueous solutions. The results showed that the nature and the concentration of the DESs used as co-solvents significantly affected the catalytic activity and stability of tyrosinase, while the immobilization enhanced the activity of the enzyme in comparison with the non-immobilized enzyme up to 3.6-fold. The biocatalyst retained the 100% of its initial activity after storage at -20 °C for 1 year and the 90% of its activity after 5 repeated cycles. Tyrosinase mCLEAs were further applied in the homogeneous modification of chitosan with caffeic acid in the presence of DES. The biocatalyst demonstrated great ability in the functionalization of chitosan with caffeic acid in the presence of 10% v/v DES [Bet:Gly (1:3)], enhancing the antioxidant activity of the films.
摘要：
在生物催化领域,实施可持续过程，如酶固定化或使用环保溶剂，像深共晶溶剂（DES）是至关重要的。在这项工作中,酪氨酸酶是从新鲜蘑菇中提取的，用于无载体固定化，以制备非磁性和磁性交联酶聚集体（CLEA）。对制备的生物催化剂进行了表征，并在许多DES水溶液中评估了游离酪氨酸酶和酪氨酸酶磁性CLEAs（mCLEAs）的生物催化和结构特征。结果表明,作为共溶剂的DES的性质和浓度显著影响酪氨酸酶的催化活性和稳定性,与未固定化酶相比，固定化酶的活性提高了3.6倍。生物催化剂在-20°C下储存1年后保持其初始活性的100%和在5个重复循环后其活性的90%。在DES存在下，酪氨酸酶mCLEAs进一步应用于咖啡酸对壳聚糖的均相改性。在存在10％v/vDES[Bet：Gly（1：3）]的情况下，生物催化剂在用咖啡酸对壳聚糖进行官能化方面表现出很大的能力，增强膜的抗氧化活性。
