The culture medium containing the degradation products after
the incubation period were centrifuged and the supernatants were
extracted thrice with equal volume of ethyl acetate and dried over
anhydrous Na2SO4. The solvent was evaporated in a rotary
evaporator (SUPERFIT, PBU-6). Gas chromatography (Thermo
TRACE ULTRA GC) equipped with mass spectrometry (TSQ
QUANTUM) detector was used in the analysis of ethyl acetate
extract. Helium (99.999%) was used as the carrier gas with a flow
rate of 1.5 ml min1 in the split less mode. An aliquot of 1ml of the
sample was injected into the column. The oven temperature was
programmed from 40 C (isothermal for 2 min), with an increase of
12 C min1, to 300C ending with an isothermal at 300 C for
5 min. Both the injector and auxiliary temperatures were set at
275 C, respectively. Ion source temperature was maintained at
225 C. The mass spectrum of compounds in samples was obtained
by electron ionization at 70 eV and the detector was operated in
scan mode from 45–450m/z. The total running timewas 28.67 min.
Identification was based on the molecular structure, molecular
mass and calculated fragments. Interpretation on mass spectrum
GC–MS was conducted using the database of NIST, Library. The
spectrum of the unknown component was compared with the
spectrum of the component stored in the NIST library.