Casein tryptone

The gene encoding leaf-branch compost cutinase (LCC, GenBank: AEV21261), TrCBM (GenBank: AGI55989.1) and CfCBM (GenBank: P07984.1) were synthesized by Sangon Biotech (Shanghai, China) and the gene sequences of fusion proteins were listed in Table S7. E. coli BL21(DE3) and DH5α were purchased from TransGen Biotech (Beijing, China). The pET-26b(+) plasmid was obtained from GenScript (Nanjing, China). Ni²⁺-Sepharose 6FF was purchased from Solarbio (Beijing, China). Q5 high-fidelity 2× master mix^®, DpnI and T4 DNA ligase were purchased from New England Biolabs (Beijing, China). Yeast extract, casein tryptone, agar, kanamycin, ampicillin, PET granules, BHET, MHET and TPA were obtained from Sigma-Aldrich (Shanghai, China).

Pre-cultures for quark fermentation were obtained by inoculating L. lactis ssp. cremoris MG1363 in M17 media supplemented with 0.5% (w/v) carbon source and incubated overnight at 30 °C, with aeration (aerobic fermentation at 120 rpm) or without aeration (static fermentation). The quark making procedure is modified from Binda and Ouwehand [28 ]. Together with 45 ml pasteurised skim milk (Jumbo Biologische houdbare Magere Melk, Netherlands), 0.5% (w/v) carbon source, 1% (w/v) casein tryptone (Sigma) and 1% (v/v) pre-culture were added to 50 ml centrifuge tubes. Fermentation took place at 20 °C or 30 °C for 20 h, and the pH values of samples were checked to be similar to traditional quark products (4.6). After centrifugation at 3000×g for 10 min, the whey was discarded to obtain quark products.