Development of an alternative low-cost culture medium for a new isolated high-production DHA strain using kitchen wastewater

Docosahexaenoic acid (DHA) is a high-value polyunsaturated fatty acid. The industrial development of microbial DHA was restricted due to high medium cost. Kitchen wastewater was always rich in nitrogen, phosphorous, carbohydrates, which can be used for microorganism growth. This study developed of a primitive low-cost culture medium for a new isolated high-production DHA strain using kitchen wastewater. The results showed that, a total of 66 strains were isolated from mangrove habitats. The highest DHA-producing strain N6 was identified as Aurantiochytrium sp. (GenBank accession number OL455742) with a DHA production of 6.56 g/L. Then the optimization of kitchen wastewater medium was designed by Response Surface Methodology, and 7.14 similar to 7.23 g/L of DHA production was obtained. At the same time, the lipid content in Aurantiochytrium sp. N6 was as high as 75.68%, which contributed to the increase of DHA production in optimal kitchen wastewater medium. Finally, the substrate cost of kitchen wastewater medium was reduced by 43.95%. Meanwhile, the dissolved organic carbon (DOC), dissolved nitrogen (DN) and dissolved phosphorus (DP) in kitchen wastewater were utilized by Aurantiochytrium sp. N6 more than 90%. This work enriched the competitive candidate DHAproducing microbes, and provided a perceptive idea for both the medium substrate cost reducing and kitchen wastewater recycling.