Zhengyu Wang;Ying Xu;Hao-Yun Wang;Jian Zhao;Gao Dongmei;Fengmin Li;Baoshan Xin

Chemical and Mineral Metal Material Testing Center, Tianjin Entry-Exit Inspection and Quarantine Bureau, Tianjin 300456 (China); Department of Plant, Soil and Insect Sciences, University of Massachusetts, Amherst MA 01003 (USA);College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100 (China); Department of Plant, Soil and Insect Sciences, University of Massachusetts, Amherst MA 01003 (USA;College of Animal Science and Veterinary Medicine, Qingdao Agricultural University, Qingdao 266109 (China); College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100 (China)

beads;immobilized;sad;crude oil;systems;0

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 x 10(4) colony forming units (cfu) kg(-1) (low concentration, L), 5 x 10(4) cfu kg(-1) (medium concentration, M), and 1 x 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.