Production method of α-arbutin

(1) Biotransformation method

Biotransformation mainly uses enzymes in organisms to carry out enzymatic reactions to exogenous compounds. The cell tissue of organisms can be a bioreactor or a source of enzyme catalysts. The method has good stereoselectivity, environmental friendliness, few by-products, simple operation, and is suitable for mass production of α-arbutin.

(1.1) Plant cell tissue as a bioreactor to synthesize α-arbutin

The method utilizes the glycosylase in the organism to convert exogenous hydroquinone into arbutin. The yield is higher and the stereoselectivity is better. Plant cell tissue as a bioreactor to synthesize arbutin, the key lies in the selection of plant tissue culture medium and the determination of transformation conditions. Different kinds of plant tissue cultures have a great influence on the conversion rate of hydroquinone.

(1.2) Synthesis of α-arbutin by microbial cell transformation method

The method is mainly to selectively synthesize α-arbutin through the catalysis of glucose and hydroquinone by different microbial metabolic enzymes.

(2) Enzyme synthesis

(2.1) Glycosidase is mainly used to cleave glycosidic bonds in organisms, but under certain conditions, it can catalyze the synthesis of glycosides through reverse hydrolysis and glycosyl transfer reactions. The process of synthesizing α-arbutin by glycosyl transfer reaction catalyzed by glycosidase is shown in the figure below. By selecting appropriate enzymes and controlling the reaction conditions, the primary hydrolysis of the glycosyl donor and the secondary hydrolysis of the product arbutin can be controlled.

(2.2) α-Cyclodextrin glucosyltransferase catalyzed synthesis of α-arbutin

Transglucosylation reaction: CaCl2 (5 mmol/L), hydroquinone (150 mmol/L), and maltodextrin 60 g/L were added to a 20 mmol/L pH 6.0 citric acid-phosphate buffer system The samples were reacted with 0.025 mg/mL α-cyclodextrin glucosyltransferase at 40 °C, 100 r/min water bath shaker for 24 h, and the samples were inactivated in boiling water bath for 5 min.

Hydrolysis reaction: Amyloglucosidase was added to the samples after high temperature inactivation, reacted for 4 h in a water bath shaker at 40 °C, 100 r/min, and then inactivated in a boiling water bath for 5 min. After centrifugation, high performance liquid chromatography (HPLC) ) analyze.

The following table investigates the effects of glucose, maltose, and maltodextrin (DE value 4%-6%, 8%-10%, 10%-15%) as donor substrates of α-arbutin on the reaction respectively. It can be seen from the table that in addition to glucose, maltose and maltodextrin can be used as donor substrates to generate α-arbutin, among which α-arbutin with DE value of 8% to 10% maltodextrin is used. The highest yield was 2.61 g/L.