Screening of activity towards decanoic acid. The biotransformations were performed using purified protein with a final enzyme concentration of 10 or 50 μM. Decanoic acid was added from 80 mM stock solution in DMSO, to give a final concentration of 0.5 mM (0.6% v/v final DMSO concentration). The reactions were in 0.1 M potassium phosphate buffer, pH 8, up to a final volume of 200 μL, and utilised a NADPH-regenerating system consisting of glucose dehydrogenase (GDH; 1 mg mL -1 , CDX-901, Codexis), NADP + (1 mg mL -1 ) and D-glucose (10 mg mL -1 ). The reactions were conducted in triplicate and incubated for 20 h, at 30 °C, and with agitation at 200 rpm.All biotransformations were worked up by quenching initially with 10 μL 5 M HCl (0.1 M), followed by the addition of an equal volume of dichloromethane containing nonanoic acid (1 mM) as an internal standard. The samples were centrifuged (20 627 g, 10 min); the organic phase was separated and dried with MgSO4, and centrifuged again (20 627 g, 10 min); and then samples were derivatised with N-methyl-N-(trimethylsilyl)trifluoroacetamide (MTSFA, 20 μL) for 15 min at 50 °C for GC-MS analysis. The GC system (Santa Clara, CA, USA) was coupled to an MS detector (Agilent Technologies) and Agilent HP-1 MS column (30 m x 0.32 mm x 0.25 µm) with helium gas as the carrier. The GC-MS method was 120 °C held for 4 min, increased to 200 °C at a rate of 20 °C min -1 then held at 200 °C for 2 min.