Bacterial decolourization enhancement using a constructed mixed consortium

This study provides an attempt to construct a mixed consortium in high decolourization efficiency to a model dye- reactive red 22, since pure cultures of decolourizer have less colour removal capability in dye-bearing wastewater treatment. In the preceding study, we unintentionally found coexistence of DH5α and Pseudomonas luteola resulted in an enhancement for decolourization. Although non-decolourizers (Escherichia coli DH5α) were considered metabolically "dormant" in the constructed mixed consortium, their presence still significantly enhanced decolourization performance of the decolourizers (P. luteola). The crucial finding of this study indicates that DH5α serves as an active microorganism for biodecolourization enhancement. This "altruistic" characteristics of DH5α in mixed consortia gives rise to higher decolourization performance than that without such beneficial interaction (i.e., pure P. luteola cultures). To indicate the contributions due to the presence of DH5α, decolourization performances at various pHs, temperature, dissolved oxygen, and dye concentrations were evaluated. Results of repeated batch cultures also showed that consecutive acclimation of P. luteola significantly increased decolourization capability due to longer "age" in dye-containing environments for higher azo-reductase activity. This also supported progressive increases in decolourization performance in sequencing batch cultures. Extracellular metabolites released by non-decolourizers DH5α considerably enhanced the decolourization of P. luteola.