Enhanced phenol biodegradation and aerobic granulation by two coaggregating bacterial strains

The effect of coaggregation of the two bacterial strains Propioniferax-like PG-02 and Comamonas sp. PG-08 on phenol degradation and aerobic granulation was investigated. While PG-02 was characterized as a phenol-degrader with a low half-saturation kinetics constant, PG-08 possessed strong aggregation ability with poor phenol degradation ability. The two strains coaggregated through involvement of lectin-saccharide interactions with the adhesin protein on strain PG-02 and the complementary sugar receptor on strain PG-08. Using the V. harveyi reporter strain BB170, it was found that both strains could produce autoinducer-2-like signals. If incubated together, the two strains showed cooperation for phenol degradation. In batch, the coculture degraded phenol at an initial concentration of 250 mg L-1, faster than each strain separately. Bioaugmentation with simultaneously the two strains in sequencing batch reactors significantly improved phenol removal and aerobic granulation as compared to monoculture bioaugmentation. Bacterial coaggregation might be an integral component of the aerobic granulation process. Investigation of in situ occurrence of coggregation in aerobic granulation would help unveil its molecular mechanism. Then the granulation process could be improved through selection of specific microbial groups.