Cell lysis was performed by freezing and thawing cycles. Frozen cell pellets were resuspended in each 300 µl Tris•SO4 buffer, pH 7.0 supplemented with 1 mg mL -1 lysozyme and 1 pierce protease inhibitor tablet (Thermo Fisher Scientific) per 10 mL. The cell suspension was incubated at 30 °C and 700 rpm for 1 h before freezing at -20 °C for 30 min. The cell suspension was thawed again and incubated for another 1 h at 30 °C and 700 rpm. After the first 30 min, 50 µL DNaseI-solution (0.1 mg mL -1 DNase in 20 mM MgSO4) was added. Afterwards, the suspension was centrifuged (3494 g, 60 min, 4 °C) and the resulting cell free extract (CFE) was used for library screening.