Survival of alkane-degrading microorganisms in biogas digestate compost in microcosm experiments

Abstract

The objective of the study was to investigate composted biogas digestate as a suitable carrier for the microorganisms to be used in bioremediation of petroleum hydrocarbon contaminated soils. The survival kinetics of alkane-degrading microorganisms was examined in microcosm experiments by two means: measuring the number of colony forming units and their ability to produce CO2 from alkanes. The viability of the cells of Rhodococcus strains in the compost lasted longer than those of the tested Brevundimonas, Chryseobacterium, Pseudomonas strains. The decimal reduction time (D-value) used to express the survival of the microorganisms depended on their cell structure and biological features. Their survival was also affected by some abiotic factors: higher temperature (26 °C) decreased the survival of the microbes while the addition of burned perlite to the compost medium increased it. All of the tested microorganisms were able to use diesel oil as a sole carbon source both in the pure, unamended compost and in the compost-perlite mixture. Moreover, the addition of perlite increased the alkane-degrading activity for the tested Rhodococcus and fungal strains. These results indicate that biogas digestate composts can be suitable carriers for microorganisms used in bioremediation. © 2014, ALÖKI Kft., Budapest, Hungary.