Fungal strains were isolated from honey bee bread collected in Kamenny Malikov, Czech Republic (49°12′51.533″ N, 15°7′5.129″ E) in March/April 2019. Following their characterization, they were deposited as Talaromyces strains in the Fraunhofer strain collection (EXT111748–EXT111754). Seven strains were cultivated in duplicate on Sabouraud dextrose agar (SDA) for 1 week at 25 °C. The mycelia were transferred to a 100 mL malt peptone medium comprised of 30 g/L Difco malt extract (Thermo Fisher Scientific, Hessen, Germany) and 5 g/L mycological peptone from meat (Carl Roth, Karlsruhe, Germany) at pH 5.4 ± 0.2. The cultures were incubated at 28 °C for 6 h, shaking at 175 rpm (ø = 50 mm), and then at 26 °C and 70% relative humidity for a further 18 days as a static culture.
The cultures were freeze-dried and extracted with HPLC-grade methanol (VWR Chemicals, Darmstadt, Germany). Briefly, we added 40 mL of methanol and incubated the samples in an ultrasonic bath for 5–10 min before shaking them for 2 h at 175 rpm (ø = 50 mm). The samples were then passed through filter paper, and the extraction process was repeated. The crude extracts were then dried in preweighed Falcon tubes using a rotary vacuum concentrator (Christ, Frankfurt, Germany), redissolved in 80% acetone, and diluted to a final concentration of 8 mg/mL. The crude extracts and diluted stocks were stored at –20 °C.
The cultures were freeze-dried and extracted with HPLC-grade methanol (VWR Chemicals, Darmstadt, Germany). Briefly, we added 40 mL of methanol and incubated the samples in an ultrasonic bath for 5–10 min before shaking them for 2 h at 175 rpm (ø = 50 mm). The samples were then passed through filter paper, and the extraction process was repeated. The crude extracts were then dried in preweighed Falcon tubes using a rotary vacuum concentrator (Christ, Frankfurt, Germany), redissolved in 80% acetone, and diluted to a final concentration of 8 mg/mL. The crude extracts and diluted stocks were stored at –20 °C.