Potato dextrose agar medium

Wheat Qu were collected from a huangjiu-making factory (30°08′ N, 120°49′ E) in Shaoxing, Jiangsu Province, China in September, 2020. For microbial isolation on laboratory culture medium, wheat Qu samples were suspended in sterile distilled water, and serial dilutions were plated onto potato dextrose agar (PDA) medium (Solarbio, Beijing, China) for incubation at 28 °C for between 3 and 7 days. Single colonies were isolated, purified, and purified isolates preserved in 30% v/v glycerol at −80 °C. The isolated strains were spotted in triplicate on ethyl ferulate (EFA) agar [37 (link)], carboxymethylcellulose sodium (1% w/v, CMC-Na) agar, or xylan (0.5% w/v) agar selective solid media for the detection of feruloyl esterase (FAE), carboxymethyl cellulase (CMCase), and xylanase by qualitative and semi-quantitative agar spot methods [38 (link)]. The plates were incubated at 28 °C for 3 days to allow the secretion of enzymes. The enzymatic activity index (EI) was calculated as the ratio between the mean diameters of the substrates’ degradation halos and the average diameters of colonies [39 (link)]. All the chemicals used in the medium were reagent grade from Solarbio (Beijing, China) and Sinopharm (Shanghai, China).

A. niger CICC 2214 and A. niger CICC 41481 were all sourced from China Center of Industrial Culture Collection (CICC). M. anka GIM 3.592 was sourced from Guangdong Microbial Culture Collection Center (GDMCC). Eurotium cristatum FEc.1-1 was generously provided by Professor Ling Tiejun from Anhui Agricultural University. All four fungi were maintained on Potato Dextrose Agar (PDA) medium purchased from Solarbio (Shanghai, China). For solid-state fermentation (SSF), specific amounts of substrates were prepared for each strain. In Petri dishes with a diameter of 75 mm, the mixture of 0.5 g of rice flour and 3.0 g of grape pomace seed powder was used as the substrate for M. anka SSF, while the mixture of 0.8 g of rice flour and 3.0 g of grape pomace seed powder was used for E. cristatum SSF. Additionally, 1.0 g of grape pomace seed powder was used as the substrate for A. niger SSF.