Abstract

Anthocyanidins are one subclass of flavonoids in plants and possess important biological functions. They are not only natural and safe pigments, but also have various health-promoting effects for human. Dihydroflavonol 4-reductase (DFR) is a pivotal enzyme in the biosynthesis of anthocyanidins and other flavonoids in plants. DFR is responsible for catalyzing the reduction of dihydroflavonols to leucoanthocyanidins, which can be further converted into anthocyanidins by either enzymatic or chemical reactions. However, there are few studies on the efficient and green synthesis of anthocyanidins by in vitro biocatalysis currently. Here, we prepared magnetic Fe3O4/PVIM/Ni2+ nanoparticles as nano-carriers to immobilize a histidine-tagged DFR fusion enzyme acquired from the recombinant expression of the DFR gene of the tea plant. The DFR enzyme and the nano-carrier were connected based on specific affinity. The immobilization conditions were optimized. The nanoparticles and Fe3O4/PVIM/Ni2+-immobilized DFR enzyme were characterized by SEM, TEM, PSA, FT-IR, XRD and SQUID techniques. Compared with free enzyme, the immobilized DFR enzyme has better thermal stability, higher acid tolerance and relatively good reusability, and also reduces the inhibitory effect of metal ions and organic reagents on enzyme activities. This work developed a new nano-immobilized DFR enzyme that enriches the green synthesis method for the production of anthocyanidins.