Sodium dihydrogen phosphate

Yeast extract and tryptone were purchased from Oxoid (Shanghai, China). Pyridoxal-5’-phosphate (PLP), pyruvate and R-1-phenylethylamine (1-(R)-PEA) were purchased from Aladdin Biochemical Technology Co., Ltd. (Shanghai, China). Choline chloride (ChCl), urea, ethylene glycol (EG), propylene glycol (PG), glycerol, formate, kanamycin sulphate, isopropyl–β-d-thiogalactopyranoside (IPTG), sodium dihydrogen phosphate, disodium phosphate, imidazole, sodium chloride, Ni-NTA Sefinose™ Resin (Settled Resin), Modified Bradford Protein Assay kit and SDS PAGE gel kit were obtained from Sangon (Shanghai, China). Amicon^®® Ultra Filter units were obtained from Sigma Aldrich (Shanghai, China). All chemicals were of analytical grade. The transaminase genes from Aspergillus terreus, which were previously transformed in E. coli BL21 (DE3) pRSF-D-AAO competent cells, were stored in our laboratory at −80 °C. The plasmids and the E. coli BL21 (DE3) pRSF-D-AAO competent cells were constructed by Anhui General Biology Company (Anhui, China).

Pigment standards including chlorophyll a, violaxanthin, vaucheriaxanthin, and β-carotene were purchased from Sigma-Aldrich Chemical Co. (Shanghai, China; http://www.sigmaaldrich.com). Silica gel (200–300 mesh) was obtained from Qing Dao Marine Chemical Co. (Qingdao, China). HPLC-grade solvents used for HPLC analysis were purchased from Guangzhou Runhao Biotech Co. (Guangzhou, China), such as methanol, acetonitrile, acetic ether, and dichloromethane. Other analytical solvents (n-hexane, methanol, and acetone) used in extraction and isolation of violaxanthin were purchased from Guangzhou Runhao Biotech Co. (Guangzhou, China). Deionized water was prepared by a Milli-Q water purification system (Millipore Corp., Bedford, MA, USA).
Chemicals used for their antioxidant activity including 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), potassium persulfate, ferrous chloride, potassium ferricyanide, trichloroacetic acid, hydrogen peroxide, ascorbic acid, sodium dihydrogen phosphate, and disodium hydrogen phosphate were obtained from Sangon Biotech Co. (Shanghai, China).

Yeast Peptone Dextrose (YPD) and Man Rogosa Sharpe (MRS) medium, analytical reagent of pepsin, trypsin, and bile extract were obtained from Yuanye Bio-Technology Co., Ltd. (Shanghai, China). Analytical reagent of citric acid, HPLC-grade of acetic acid, formic acid, and concentrated hydrochloric acid were purchased from MACKLIN (Shanghai, China). Analytical reagent of L-tyrosine, Folin-Ciocalteu’s reagent, casein, pyrogallol, glucose, sodium chloride, rutin, dibasic sodium phosphate, sodium dihydrogen phosphate, sodium bicarbonate, ethylene diamine tetraacetic acid (EDTA), Tris (hydroxymethyl) methyl aminomethane (Tris) were purchased from Sangon biotech (Shanghai, China). Phenolic and organic acid standards were purchased from Solarbio (Solarbio, Beijing, China), with the purity ≥98%. Deionized water was produced by a Milli-Q water purification system (Rephily RS2200QUV purist water system, Shanghai, China).