As the hexane was completely removed, the pan was kept in a desiccator before weighting. The remaining in the pan was called total hydrocarbon. In the sonicationhexane extraction, dried filter with cell was placed in 50-mL glass tube containing 30-mL hexane. The tube was put into a sonicator with frequency of 60 Hz for I h. The mixed suspension was centrifuged and extracted the total hydrocarbon as mentioned above. In the combined grinding-and-sonication-hexane extraction, the dried filter with cell was manually ground and mixed with 30-mL hexane prior to sonication and extracted the total hydrocarbon in the similar manner. Total hydrocarbon yield was
calculated from [extracted hydrocarbon (g L·I) x 1001cell dry weight (g L·I)].
3.