초록
<P><B>Abstract</B></P> <P>Fermentation wastewater (FW) and algal residue are major by-products of docosahexaenoic acid (DHA) fermentations utilizing <I>Schizochytrium</I> sp. In order to reduce production costs and environmental pollution, we explored the application of FW and algal-residue extract (AE) for DHA production. Components analysis showed that FW and AE contained some mineral elements and protein residues, respectively. When they were used for DHA fermentation, results showed that 20% replacement of fresh water by FW and 80% replacement of yeast extract nitrogen by AE reached DHA content of 22.23 g/L and 27.10 g/L, respectively. Furthermore, a novel medium that utilizes a mixture of FW and AE was applied for DHA fermentation, whereby the final DHA yield reached 28.45 g/L, 24.56% higher than conventional medium. The strategy of valorizing fermentation waste provides a new method for reducing the costs and reducing environmental pollution of microbial fermentations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A strategy of using fermentation waste by-product for DHA production was developed. </LI> <LI> Lipids extraction process was combined with by-product pretreatment. </LI> <LI> Algal-residue extract was a novel available nitrogen source to replace yeast extract. </LI> <LI> Low replacement ratio of fresh water by fermentation wastewater was beneficial to DHA production. </LI> </UL> </P>