BIOAUGMENTATION OF ACRYLAMIDE-DEGRADING BACTERIA IN THE MICROBIOTA OF RIVER SLUDGE

Abstract

Introduction. Bioaugmentation is an in situ bioremediation approach, which implies the introduction of a population of microorganisms with certain biodegrading abilities. Acrylamide is a biodegradable toxic substance. Our goal was to assess the survival of allochthonous bacterial cultures Alcaligenes faecalis 2 and Acinetobacter guillouiae 11h when introduced into river sludge and the efficiency of acrylamide decomposition by sludge with introduced amidase-containing bacteria. Methods. The microbiota of sludge from small rivers of Perm Territory was inoculated with the biomass of strains A. faecalis 2 and A. guillouiae 11h, which have amidase activity. In a laboratory experiment, we studied the survival of these bacteria as well as the biodegrading ability of the microbiota in relation to acrylamide after 3 and 6 months of incubation at 5 and 25°C. The transformation of acrylamide was assessed by HPLC, the biodiversity of river sludge was assessed by the method of metagenomic sequencing of 16S rRNA genes. Results. Incubation of sludge at 25°C for 3–6 months deteriorates the biodegrading abilities of the microbiota in relation to acrylamide, and the transformation of this pollutant occurs only during the augmentation of the biomass of amidase-containing bacteria, with acinetobacteria having an advantage over bacteria of Alcaligenes sp. Upon incubation of sludge at 25°C, the phylogenetic diversity increases, and the proportion of representatives of the phyla Actinobacteria, Chloroflexi, Ignavibacteriae, Candidatus Saccharibacteria, Acidobacteria increases as well, while the phylum Proteobacteria accounts for most of the bacterial biota in all samples, and the phylum Firmicutes accounts for 10–30%. The presence of representatives of Alcaligenes sp. and Acinetobacter sp. was confirmed in the microbiota of bioaugmented sludge after 6 months of incubation at 25°C. When incubated at 5°C, the microbiota of native sludge is capable of degrading acrylamide, but at a rate several times lower than during bioaugmentation. After incubation of Danilikha River sludge with the introduced biomass of strains A. guillouiae 11h and A. faecalis 2 at 5°C for 6 months, the complete transformation of acrylamide was observed in 4 and 20 days, respectively, with native sludge — in 35 days.