Valorization of dairy wastewaters: large biomass and hydrogen production using an alga-bacterium consortium

Description

The microalgae Chlamydomonas reinhardtii and the bacterium Microbacterium forte have been successfully cultivated as a consortium for the bioremediation of simulated dairy wastewater (sDWW) and raw DWW with high organic loads (Chemical Oxygen Demand (COD) of 12,000 and 7,346 mg·L-1, respectively). The coculture allowed the obtaining of large amounts of biomass (up to 11.27 g·L-1/ 1.25 g·L-1·d-1) and the production of biohydrogen (up to 185.8 mL·L-1 after 14 days) when cultivated in sDWW. Moreover, the use of cocultures reduced CO2 emissions (71-89%) compared to sole bacterial cultures. Supplementation with trace elements was sufficient to allow the consortium to grow in DWW without requiring other major nutrients such as carbon, nitrogen or phosphorus. Illumination at 120 µmol photon·m-2·s-1 and no agitation were identified as optimal growth conditions. Chlamydomonas and M. forte established a mutualistic relationship that facilitated substantial growth of both the bacteria and the alga. The proteolytic activity of M. forte and the subsequent release of ammonium, along with the excretion of acetic acid by the bacterium, represent the core of the mutualistic relationship that enabled significant mixotrophic growth of Chlamydomonas. This study presents potential solutions for the bioremediation and valorization of DWW with high organic loads, where the use of pre-treatment methods is not feasible on an industrial scale.

Institutions

Categories

Funding

Licence