Neutral protease

Auricularia polytricha No.10 strain was purchased from Jiangsu Tianda Institute of Edible Fungi (Jiangsu, China).
Bovine serum albumin (BSA), Coomassie brilliant blue G–250, and ascorbic acid were obtained from Aladdin Reagent Co., Ltd. (Shanghai, China). Concentrated sulfuric acid, phosphoric acid, salicylic acid, trichloroacetic acid (TFA), anhydrous alcohol, acetone, anhydrous ether, glucose, sucrose, fructose, maltose and lactose, urea, peptone, ammonium sulfate, yeast and corn starch, neutral protease, 30% hydrogen peroxide (H₂O₂), phenol, Vitamin C (Vc) sodium hydroxide, ferrous sulfate (FeSO₄), ferric chloride (FeCl₃), sodium dihydrogen phosphate, disodium hydrogen phosphate, and potassium ferricyanide [K₃Fe(CN)₆] were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). The monosaccharide Standards including fucose (Fuc), rhamnose (Rha), arabinose (Ara), mannose (Man), galactose (Gal), glucose (Glc), xylose (Xyl), fructose (Fru), galacturonic acid (GalA), glucuronic acid (GlcA), 2,2–diphenyl–1–picrylhydrazyl (DPPH), and potassium bromide (KBr, Spectrum pure grade) were purchased from Sigma Chemical Co. (St. Louis, MO, United States). All chemicals and solvents used in the current work were of analytical grade.

Fresh flowers and buds of SJL and RPL were obtained from indigenous trees (Zhaohe town, Nanyang, Henan Province, China), then dried in an oven (Binder, Neckarsulm, Germany) at 50 °C for 6 h. The dried samples were crushed to powder with a pulverizer (Wuyi Haina Electric Co., Ltd., Jinhua, China) and sieved through a 100-mesh screen. Rutin (≥98%), gallic acid (≥98%), α-amylase (10,000 u/mL), neutral protease (100 u/mg), and amyloglucosidase (100,000 u/mL) were obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).