Psychrophilic bacterial communities for biological treatment of wastewater at low temperatures

Augelletti, Floriana [UCL] Gerin, Patrick A. [UCL] Agathos, Spiros N. [UCL] Stenuit, Benoit [Yachay Tech University, Ecuador]

Psychrophiles have the potential to thrive efficiently at low and moderate temperatures using cold-adapted enzymes (Margesin, Feller et al. 2003, Margesin and Shinner 1999, Feller and Gerday 2003). Therefore, the applications of psychrophilic bacteria for specific clean-up operations (e.g., carbon removal in water resource recovery facilities) might be advantageous in cold and temperate climates. The research seeks to construct artificial bacterial consortia for the treatment of synthetic wastewater at 4°C. and to understand the link between microbial community biodiversity (e.g., species richness and functional diversity) ecosystem functionality and robustness. In particular two hypotheses will be tested for complete carbon removal:1) positive net biodiversity effects are predominantly driven by functional complementarity between species; 2) the increase of biodiversity ensures higher stability of ecosystem functioning under disturbances (e.g., wastewater strength fluctuations and salt stress). A synthetic wastewater, simulating a real municipal one, has been formulated on the basis of the unit Population Equivalent measured in Belgium (750 mg O2 L-1 COD (chemical oxygen demand), 55 mg L-1 Ntot, 11 mg L-1 Ptot). The collection of psychrophiles is made from commercial and new isolated bacteria. Synthetic psychrophilic mixed cultures (up to 4 different strains) are constructed in batch reactors using a full factorial design and tested for their degradation ability under normal operating conditions or under disturbances. Six commercial strains (DSMZ resources) have been screened for their ability to grow on the synthetic wastewater at 4°C. Two other new strains have been isolated in our laboratory and identified as Rhodococcus sp. and Pedobacter sp using the sequencing of almost full-length 16S rRNA genes. The preliminary biodegradation assays using individual pure cultures have shown an incomplete ability in the removal of the total organic content (up to 50 % of initial COD). All the strains are unable to completely consume the total organic content, indicating that the use of bacterial consortia (containing different bacterial species) could be a promising strategy to favour positive species interactions (facilitation) and complementary resource use (niche differentiation). This work can provide new insights into the relationships between biodiversity, community functioning and robustness as well as the applications of psychrophilic bacterial formulations to treat wastewater in cold environments and complement the commonly used mesophilic communities.