Our studies on soil bioremediation, wastewater treatment and air biofiltration embrace a broad range of methodical approaches and target microorganisms. Application of biostimulation and bioaugmentation tools provide a great variety of biodegradation scenarios under contrast/seasonal/globally changing environmental conditions. Soil bioremediation: our studies showed a stimulating effect of the cabbage leaf extract (amended with molasses and inorganic salts) on the bacterial degrading activity towards nitroaromatic compounds . The biomass preparation mode for bioaugmentation also plays an imperative role in increasing efficiency of biodegradation processes. In our earlier study, a population–reaction model based on a combination of microbial experimental ecosystems and a hierarchical dynamic model was tested on the consortium of eight bacterial cultures belonging to the Pseudomonas spp. and Stenotrophomonas maltophilia groups. Serial batch cultivations (seven days each) with a stepwise increase (1%, 3%, 5% w/w) in diesel oil concentration resulted in a considerable increase of biomass, production of biosurfactants and enzyme activity at the second step, i.e., with 3 % diesel oil. Furthermore, molasses concentrations below 1 % are likely to be more efficient for microbial activity when grown with diesel oil. Wastewater treatment: biodegradation of pharmaceutical residues has been studied with emphasis on bioaugmentation and combined biodegradation/biosorption . The response of microbial community of activated sludge to ibuprofen (IBP) was studied at the concentrations of 50–5000 mg/L. Batch incubation was performed in an OxiTop® device for 21 days. Massive DNA sequencing analysis of the activated sludge revealed that Proteobacteria became more dominant when grown in the presence of IBP. Incubation of activated sludge in the presence of 1000 mg/L IBP led to an increased occurrence of ciprofloxacin-resistant bacteria. The predominance of Enterobacteriales in the activated sludge is suggested as one of the possible explanations of the enhanced resistance to ciprofloxacin. Industrial wastewaters were tested for the presence of heterotrophic nitrifiers. It has been suggested to strengthen the role of heterotrophic nitrifiers in the treatment of industrial wastewaters, where toxicity obstacles inhibited nitrification under conventional conditions. Air biofiltration: Our experiments with hydroponic cultures in the green wall system module, which provides air biofiltration and automatic irrigation, showed a significant (p<0.05) effect of bioaugmentation for the growth of Mentha aquatica after 47 days of vegetation. Sewage sludge treatment: sewage sludge (SS) disposal is one of the greatest challenges of the 21st century. It was recently reported, that wheat straw stabilized the SS better than faba bean straw and wood-chip pellets. Treatment of SS lead to an increase of Firmicutes, i.e., 32.70–53.84%. The incubated non-amended SS showed an increase in virus abundance. Bioaugmentation and amendments increased the yield of gene families GO ID.
An improvement of the biodegradation performance is related the problems of long-term residence of special functional bacteria and maintenance of multi-bacteria interactions. If the total breakdown of the remaining contaminants is not achievable, immobilising and reducing the bioavailability of organic pollutants in soils is critical . Multi-compound pollution, new findings in inoculum conservation for commercial uses, and the further development of process monitoring will be the main topics for further research in the field of bioaugmentation-assisted bioremediation.
The research group: www.lu.lv/en/mbi/laboratories/laboratory-of-environmental-microbiology/
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