Application of Aurantiochytrium sp. L3W for food-processing wastewater treatment in combination with polyunsaturated fatty acids production for fish aquaculture

Thraustochytrids such as Aurantiochytrium are heterotrophic microorganisms that are known to produce valuable polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). In this study, Aurantiochytrium sp. strain L3W was used to remove dissolved organic carbon (DOC) and dissolved nitrogen (DN) from bean-boiling (BB) and miso-processing (MP) wastewater and to simultaneously produce PUFAs. Strain L3W removed 52% of the DOC and 37% of the DN from sterilized BB wastewater and produced biomass that contained 137 mg/g of fatty acids (FAs), including 96.2 mg/g of DHA. Growth of strain L3W in sterilized MP wastewater resulted in the production of biomass containing 147.6 mg/g of FAs, including 97.8 mg/g of DHA, and removal of 47% of the DOC and 55% of the DN from the wastewater. The biomass of strain L3W was digestible by the enzymes extracted from the stomachs of rainbow trout. These results confirmed the potential for use of strain L3W to remove DOC and DN from food processing wastewater and to produce PUFAs. This study also provided the first evidence that the raw biomass of Aurantiochytrium sp. can be used as a fish feed additive. [Display omitted] •Aurantiochytrium sp. strain L3W was successfully cultivated in the wastewaters discharged from a miso soup factory.•Removal of dissolved organic carbon and nitrogen and production of polyunsaturated fatty acids were confirmed.•The strain L3W produced docosahexaenoic acid in the wastewaters under sterile and unsterile conditions.•Raw biomass of the strain L3W was digestible by the enzymes in rainbow trout stomach.