Recycling Fermentation Strategy for Waste Cellular Residues in the Production of Polyunsaturated Fatty Acids

Cellular residues after lipid extraction are the primary waste by-products of microbial polyunsaturated fatty acid production. To mitigate the discharge of cellular residues and reduce the cost of DHA and ARA production, this study examined the utilization of enzymatically hydrolyzed Aurantiochytrium cellular residues (ACRs) and Mortierella alpina cellular residues (MCRs) as nitrogen sources. Results demonstrated that ACRs and MCRs could partially substitute yeast extract (YE) without adverse effects on DHA and ARA fermentation. Moreover, the implementation of a new fermentation medium incorporating ACRs, MCRs, and YE as mixed nitrogen sources resulted in DHA and ARA yields of 17.78 and 5.77 g/L, respectively. These values represented increases of 10.37% and 9.28% compared to traditional cultural methods, while simultaneously reducing the usage of YE by 80% and 60%, respectively. Therefore, the strategy of recycling waste cellular residues presents a novel approach for reducing the costs and environmental impact associated with microbial fermentations.