Although different BTEX pollutants showed different removal
dynamics, the doses of the immobilized Mycobacterium sp.
CHXY119 had almost no effect on removal efficiency (Fig. 2),
suggesting the treatment characteristic of the immobilized bead.
The immobilized bead removed BTEX in two separate steps, i.e.,
transport from the outside of the bead to the inside and then
biodegradation by the immobilized cells. In general, biodegradation
processes were relatively fast ones due to the high activity
of the immobilized cells [25]; whereas the pollutant transportation
processes relying on the thickness and structure of the beads
were slower ones as the rate-limiting step. Therefore, even lower
doses of immobilized cells were effective for bioremediation of
BTEX-contaminated groundwater.