2.5. Analysis of transesterification reactions by immobilized
LipM7-PhaP
PHB nanofibers containing immobilized LipM7-PhaP (100 mg) were added to
a 10 mL solution of 1 M octanoic acid and 1 M MeOH. The reaction mixture
was incubated at 30°C under constant orbital shaking at 250 rpm. Samples
(100 µL) were withdrawn every 12 h until the reaction reached
equilibrium. Withdrawn samples were mixed with 900 µL of chloroform
containing n-hexane as an internal standard. Synthesized methyl
octanoate, and residual octanoic acid and methanol were analyzed by gas
chromatography on an HP-5 capillary column (30 m × 0.32 mm × 0.25 µm,
J&W Scientific; Agilent, Santa Clara, CA) equipped with a flame
ionization detector (FID). Helium was used as the carrier gas at a flow
rate of 1.3 mL/min. The temperatures of the injector and detector were
set at 250°C and 340°C, respectively. Starting from 100°C, the oven
temperature was sequentially raised to 260°C (15°C/min) and 315°C
(5°C/min), and held at this temperature for 15 min. Samples (1 µL) were
injected in the split mode.