Fifty grams of cell-immobilized beads containing both Mycobacterium
sp. CHXY119 and Pseudomonas sp. YATO411 was inoculated
into spherical bottles containing simulated contaminated groundwater
consisting of 1000 ml of oxygen-saturated (about 7–8 mg l−1 of dissolved oxygen (DO)) water containing 20 mg l−1 of benzene,
toluene, ethylbenzene or p-xylene. The inoculated bottles were
incubated at 25 ◦C for reaction. During biodegradation, the DO of
the groundwater was monitored with a portable DO metre every
5 min, and the remaining dose of pollutants was measured every
1 h by GC-FID analysis of the headspace gas until DO value almost
stabilized. The oxygen uptake rate for BTEX biodegradation was
calculated as follows: