Rhamnosylation Biotransformation in G. oxydans

G. oxydans cells were grown to an OD₆₀₀ of 1.3, centrifuged (4,000 × g, 5 min) and washed twice with 50 mM phosphate buffer (pH 6). After the second washing step, cells were resuspended in biotransformation buffer (6.6 g L⁻¹ Na₂HPO₄, 3 g L⁻¹ KH₂PO₄, 1 g L⁻¹ NH₄Cl, 0.5 g L⁻¹ NaCl, 0.49 g L⁻¹ MgSO₄, 0.02 g L⁻¹ CaCl₂) supplemented with 2% (w/v) l-rhamnose and incubated for 24 h at 30°C and 200 rpm. Then, the cells were removed from the buffer (4,000 × g, 5 min) and the supernatant was used for analysis by gas chromatography (Agilent 6,890 N, Agilent Technologies) coupled to a Waters Micromass GCT Premier high-resolution time-of-flight mass spectrometer (Waters). Sample handling for derivatization, GC-TOF-MS operation, and peak identification were carried out as described (Paczia et al., 2012 (link)). As a control, samples from biotransformation buffer with l-rhamnose and without cells as well as biotransformation buffer without l-rhamnose yet with cells were prepared.