Bioremediation Potential of Biochar-Immobilized Cells of Azospirillum brasilense

— A biopreparation consisting of the cells of Azospirillum brasilense strain SR80 immobilized on wood biochar was characterized. Sorption of oil by biochar and its colonization by Azospirillum were studied in liquid medium. Oil sorption by biochar was found to decrease in the presence of microbial cells. Within the 22–45°C temperature range, the highest oil biodegradation efficiency by biochar-immobilized and suspended cells was observed at 22 and 38°C, respectively. These data were confirmed by soil experiments. Under conditions of a laboratory pot experiments, the biochar-immobilized microbial culture in combination with two plants ( Sorghum bicolor and Medicago falcata ) exhibited the highest oil removal efficiency compared to other variants. The introduced strain A. brasilense SR80 exhibited high survival in tilled soil during two-month incubation, as was confirmed by molecular biological assays. Suspended Azospirillum cells exhibited higher oil-oxidizing activity than the immobilized ones in a field experiment under real-life conditions of a hot dry summer. The present work shows high dependence of bioremediation technologies upon environmental factors and indicates the need for thorough investigation of the processes involved.