CONSTRUCTION OF A SYNTHETIC CONSORTIUM OF DENITRIFYING MICROORGANISMS FOR THE TREATMENT OF GROUNDWATER FOR HUMAN CONSUMPTION

MASSICOT, AGUSTINA; CRISTIÁN DOTTO; EVA FIGUEROLA

Los Cocos, Córdoba

Congreso; XVII Congreso Argentino de Microbiología General; 2022

Sociedad Argentina de Microbiología General

Nitrate pollution of groundwater has increased worldwide due to human activities and populationgrowth. Nitrate in drinking water is harmful to health so, in Argentina, a limit of 45 mg/L of nitrate inwater for human consumption has been set.Biological denitrification (DB) is a well-established process at the industrial level in several countries. Ittransforms nitrate into gaseous nitrogen, harmless to the environment, with lower operating costs andgreater water recovery. The DB is mainly carried out in fixed bed reactors filled with an inert material assupport for the denitrifying biofilm made up of a consortium of native microorganisms naturally selectedby the operation conditions.In a previous stage, the optimal conditions for the development of mixed denitrifying bacterialcommunities in laboratory reactors were determined. A 10X scaling up was carried out, and a pilotplant was set up in a water well affected by high nitrate levels (Llavallol, PBA). An initial startup periodof approximately 100 hydraulic retention times was observed regardless of the scale of the experiment.Based on these results, the hypothesis arises that bioaugmentation with a synthetic consortium ofindigenous microorganisms will allow for shortening the period necessary to reach a steady state. Toadvance in this sense, the first step was to obtain and characterize isolates of autochthonous bacteria.For this purpose, cultures were made under anoxic conditions from sand grains coming from laboratory-scale bioreactors, using water from the well with added nutrients as a culture medium. The growthsobtained were subjected to the streak plate method to isolate individual colonies, which were replicatedand maintained for posterior analysis. Isolates were characterized by their ability to produce gas andcapacity to accumulate nitrite. MALDI-TOF analysis was performed to rule out redundant isolates.Temperature gradient polyacrylamide gel electrophoresis was performed on 16S rRNA gene ampliconsfrom non-redundant isolates and from the bioreactor metagenome to detect those strains able tocompete successfully in the operational conditions. As a consequence, a collection of autochthonousand dominant strains in the denitrification process is available. The next step is to study their genomiccharacteristics, to establish metabolic capacities and interactions that will allow us to choose the bestpossible combination, in terms of efficiency and stability, for the assembly of the denitrifying syntheticconsortium.