Furfural

Corncob from Inner Mongolia, China, were placed in sealed plastic bags to dry naturally for about three months, ground to powder, and screened through 80 mesh before being used. The weight loss of corncob powder was less than 0.01 g/g in three months. The main components of the corncob were determined by the NREL LAP method, resulting in 35% cellulose content, 34% hemicellulose content, and 19% lignin content.
Anhydrous zinc chloride, concentrated hydrochloric acid (12 mol/L), aqueous ammonia (25–28 w%), ethyl acetate, choline chloride, oxalate dihydrate, 1,4-butanediol, glucose, xylose, furfural, 5-HMF were all purchased from Sinopharm Chemical Reagents Co., LTD. (Shanghai, China). Microcrystalline cellulose, purchased from Shanghai Aladdin reagent company (Shanghai, China). Ammonia gas, analytical pure, purchased from Anhui Hefei Hengxing Industrial Gas Co., Ltd. (Hefei, China), stored in cylinders. The flow rate is 1 mL/s.
Chromatographic grade acetonitrile for HPLC was purchased from Merck (Rahway, NJ, USA). Ultrapure water was prepared via a Milli-Q system (18.2 MΩ, Millipore, Burlington, MA, USA). The hydrochloric acid (2 mol/L) used in the experiment was obtained by diluting the concentrated hydrochloric acid and ultrapure water.

Four brands of commercial Huangjiu A, B, C, and D (14% vol.) were purchased from a local supermarket in Beijing. The edible alcohol (14% vol.) was purchased from Azelis Co., Ltd. Glucose and maltose were purchased from Yuanye Biotechnology Co., Ltd. Amino acids were purchased from Sigma‐Aldrich. Putrescine, 2‐phenylethylamine, cadaverine, histamine, tyramine, fusel oil, and acetaldehyde were purchased from Banxia Biotechnology Co., Ltd. Ethyl lactate, ethyl acetate, diethyl succinate, vanillic acid, lactic acid, succinic acid, acetic acid, phenylacetaldehyde, furfural, vitamins C, Ca, K, and Mg were purchased from Sinopharm Chemical Reagent Co., Ltd. The 5‐HT, 5‐HIAA, DA, and NO detection kits were purchased from Nanjing Jiancheng Biological Engineering Co., Ltd. A high‐purity total RNA rapid extraction kit was purchased from Beijing Biotech Biotechnology Co., Ltd. A ReverTra Ace® qPCR RT Master Mix kit was purchased from Toyobo Co., Ltd. Real‐time fluorescent quantitative primers were supplied from Beijing Huada Gene Research Center. All other chemical reagents were of analytical grade.

The microorganism used for fermentationwas Saccharomyces cerevisiae in the form of dry yeast (thermal resistant) (Angel Yeast Company Ltd, Yichang, China), which was named Angel Super-Alcohol Active Dry Yeast (starch base). The yeast was kept at 4 ^oC during storage, and was weighted and directly added to specified fermentation media as received right before each use. Filter paper activity of cellulase (CTec-2) was 150 FPU/mL, kindly provided by Novozymes Investment Co. Ltd. (Beijing, China). D-glucose (C₆H₁₂O₆·H₂O), glycerol (99 wt%), ethanol (99 wt%) were received from Sinopharm (China). Phenol, guaiacol, vanillin, levulinic acid, furfural and 5-hydrolsymethylfurfural (HMF), were received from Sinopharm (China). Polyethylene glycol were purchased from Aladdin(China). Sulphuric acid (98wt%) and methylene blue were provided by a local supplier. Deionized water (DI H₂O) was produced by a Milli-Q Integral 5 system. All other chemicals were of analytical quality.