New Biocomposite Materials Based on Hydrocarbon-Oxidizing Microorganisms and Their Potential for Oil Products Degradation

Abstract— Increasing the stability of biopreparations of hydrocarbon-oxidizing bacteria (HOB), which are used for bioremediation of oil-contaminated environmental objects, is presently an important task. In the present work, new biocomposite materials were developed for HOB immobilization on the surface of microcapsules (MCs) from: pure and chitosan- or gelatin-modified polyurea; polylactic and polyglycolic acids; and cell incorporation into the gels of humic acids silanol derivatives. The tested organisms used were gram-negative HOB Acinetobacter seifertii WS1, Pseudomonas extremaustralis WS-1, P. aeruginosa OIS 4.8.1, gram-positive bacteria Rhodococcus qingshengii 367-6, and Dietzia maris 367-2, as well as yeasts Yarrowia lipolytica 367-2. HOB cultivation in liquid media with chitosan-polyurea-based MCs (but not MCs of pure or gelatin-modified polyurea) resulted in viable cell numbers (CFU/mL) 2‒5 times higher than in the control (without MCs) both in freshly grown cultures and in those stored at room temperature under access to air for a long time (up to 7 months). HOB cultivation together with polylactic acid MCs resulted in active surface growth. Surface growth was less pronounced in the variants with polyglycolic MC, as was confirmed microscopically. Survival of the R. qingshengii grown in the presence of polylactide MCs after storage for 1 month was three orders of magnitude higher than in the control (without MCs). HOB immobilization in the gels of humate silanol derivatives was the most efficient approach, which resulted in CFU titers up to 100 times higher than in the control variant after storage for 7‒12 months; respiration rates were also higher than in the control. The biopreparations with HOB immobilized in new biocomposite materials had high oil-oxidizing activity both in liquid media and oil-contaminated soil microcosms. After 4-month storage at room temperature, the rate of oil oxidation by these biopreparations was 2 to 4 times higher than in the control. The practically important features of new biocomposite materials are: prolonged HOB cell viability in the course of long-term storage (up to 12 months); homogeneity of the cultures at the time of application; and presence of additional growth substrates, which may be used for hydrocarbon co-oxidation.