The efficiencies of free and immobilized bacterial cultures of petroleum hydrocarbon degraders were evaluated and compared in
this study. Hydrocarbon-degrading microbial communities with high tolerance to and high degrading ability of crude oil were obtained
from the soil contaminated with crude oil in the Yellow River Delta. Then, the microbial cells were immobilized in sodium alginate
(SA) beads and sodium alginate-diatomite (SAD) beads. The biodegradation of crude oil in soil by immobilized cells was compared
with that by free cells at three inoculation concentrations, 1
×
10
4
colony forming units (cfu) kg
−
1
(low concentration, L), 5
×
10
4
cfu
kg
−
1
(medium concentration, M), and 1
×
10
5
cfu kg
−
1
(high concentration, H). At 20 d after inoculation, the maximum degradation
rate in the immobilized systems reached 29.8% (SAD-M), significantly higher (
P<
0
.
05) than that of the free cells (21.1%), and the
SAD beads showed greater degradation than the SA beads. Moreover, both microbial populations and total microbial activity reached
significantly higher level (
P<
0
.
05) in the immobilized systems than free cell systems at a same initial inoculation amount. The
scanning electronic microscope (SEM) images also confirmed the advantages of the immobilized microstructure of SAD beads. The
enhanced degradation and bacterial growth in the SAD beads indicated the high potential of SAD beads as an effective option for
bioremediation of crude oil-contaminated soils in the Yellow River Delta