EFFECT OF ALGINATE ENCAPSULATION AND SELECTED DISINFECTANTS ON SURVIVAL OF AND PHENANTHRENE MINERALIZATION BY PSEUDOMONAS SP UG14LR IN CREOSOTE-CONTAMINATED SOIL

The survival and phenanthrene-mineralizing ability of free and alginat e-encapsulated Pseudomonas sp UG14Lr cells were examined in a creosote -contaminated soil. Alginate encapsulation adversely affected both sur vival and phenanthrene mineralization, This was postulated to be due t o concentration of water-soluble toxic compounds in the alginate beads , Toxicity studies showed that the concentrated water-soluble fraction of the creosote-contaminated soil may be toxic to Pseudomonas sp UG14 Lr in soil with a low moisture content. Survival of alginate-encapsula ted cells improved with increasing soil moisture content, Free cells s urvived well at a steady population of 10(8) CFU g(-1) dry soil for 28 days in the creosote-contaminated soil. However, phenanthrene mineral ization was not improved compared to the uninoculated control, This wa s attributed to the existence of indigenous phenanthrene-mineralizing microorganisms already present in this contaminated soil, The effect o f calcium hypochlorite and Germiphene on survival of and phenanthrene mineralization by free and alginate-encapsulated Pseudomonas sp UG14Lr cells in creosote-contaminated soil was also studied. Addition of 0.1 % (w/w dry soil) calcium hypochlorite reduced the introduced free cell s to below detection limits (10 CFU g(-1) dry soil) within 14 days, wh ile Germiphene had no effect on cell numbers, Phenanthrene mineralizat ion by free cells was not adversely affected by treatment with calcium hypochlorite or Germiphene. Survival of alginate-encapsulated cells a fter treatment with disinfectants was as poor as that without disinfec tion, The results show that alginate encapsulation may not be a suitab le formulation for introduction of Pseudomonas sp UG14Lr into creosote -contaminated soils.