Caffeic acid

Aflatoxin B₁ (AFB₁), zearalenone (ZEN), deoxynivalenol (DON), 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS), 2,6-dimethoxy phenol (DMP), syringaldazine (SGZ), and methyl syringate were purchased from Sigma-Aldrich (St. Louis, MO, USA). FB₁ (fumonisin B₁) and OTA (ocharatoxin A) were purchased from Pribolab (Beijing, China). DNA polymerase, T4 ligase, acetonitrile, and trifluoroacetic acid were purchased from Thermo Fisher Scientific (Waltham, MA, USA). Vanillin, p-coumaric, syringic acid, syringaldehyde, caffeic acid, 1-hydroxybenzotriazole (HBT), gallic acid, isopropyl-β-D-thiogalactoside (IPTG), and kanamycin were purchased from Solarbio (Beijing, China). Ni-NTA agarose was purchased from QIAGEN (Hilden, Germany). The fungal laccase from Ganoderma sp. was purchased from Sunson (Yinchuan, Ningxia, China). Plant extracts from E. brevicornu, C. sativus L., L. angustifolia, A. officinalis, and S. tenuifolia were purchased from Ciyuan Biotech (Xi’an, Shanxi, China). All other chemicals were of analytical grade or chromatographically pure, and were commercially available.

The phenolic composition of the samples was analyzed using a 1260 high-performance liquid chromatography (HPLC) system (Agilent, Santa Clara, CA, USA) with a diode array detector. A Sunfire C18 reverse phase chromatographic column (250 × 4.6 mm, 5 μm) (Waters, Milford, MA, USA) was used with a flow rate of 1 mL/min and a column temperature of 30 °C. The mobile phases A and B consisted of 2% (v/v) acetic acid solution (A) and 2% (v/v) acetic acid-acetonitrile solution, respectively. Gradient elution was used with the following conditions: 0 min, 5% B; 40 min, 20% B; 55 min, 27.5% B; 65 min, 50% B; 66–71 min, 80% B; 73–78 min, 5% B. The injection volume was set to 10 μL, and all phenolic compounds were detected at 200–650 nm. By comparing the retention times and UV spectra to the phenolic standards, including gallic acid, protocatechuic acid, procyanidins B1, catechin, chlorogenic acid, procyanidins B2, caffeic acid, syringic acid, epicatechin, ferulic acid, rutin, epicatechin gallate, resveratrol, and p-coumaric acid (Beijing Solarbio Science & Technology Co., Ltd., Beijing, China), the phenolic compounds in the samples were qualitatively identified. The content of individual phenolic was then calculated based on the peak area and standard curve [18 (link)].

De Man, Rogosa, and Sharpe (MRS) medium was purchased from Beijing Obosing Biotechnology Co., Ltd. (Beijing, China). Lactobacillus plantarum PA01 was isolated from pickle and registered by the China Common Microbial Collections Management Center (CGMCC No.15660). Standards for high-performance liquid chromatography (HPLC) (gallic acid, ferulic acid, catechins, chlorogenic acid, rutin, phloridzin, epicatechin, quercetin, caffeic acid, phloretin) were purchased from Solarbio (Beijing, China). Chromatographic grade acetonitrile (TEDIA, Fairfield, OH, USA) and formic acid (Kemiou, Tianjin, China) were obtained for analysis.