Valorization of Solid Food Waste as a Source of Polyunsaturated Fatty Acids Using Aurantiochytrium sp. L3W

Abstract

Purpose: This study aimed at valorizing solid food waste containing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).Methods: Aurantiochytrium sp. L3W that produces DHA and EPA was cultivated on eight types of solid food waste: sake lees (SL), crown daisy, Japanese mustard spinach (JMS), soy sauce residue, lemon peel (LP), orange peel, grape skin, and Hiroshimana old pickle (HOP). The biomass mixture of the remaining food waste and strain L3W was analyzed for DHA and EPA. To characterize the types of food waste, the leachability of dissolved organic carbon (DOC) and dissolved nitrogen (DN) were compared.Results: The strain L3W grew on both pasteurized and unsterilized food waste such as SL and JMS. Elution of DOC and DN from the food waste might be a factor affecting the growth of strain L3W.However, the strain L3W might utilize solid-state organic compounds in JMS. Despite the unsterile conditions, the biomass mixture of SL contained both DHA and EPA, whereas DHA was found in the biomass mixtures of JMS, LP and HOP, thereby con rming the valorization of these types of solid food waste. Unsterile mass cultivation of the strain L3W using SL and HOP in a 200 L tank also produced a biomass mixture containing 12.6 mg-DHA/g and 0.217 mg-EPA/g. These DHA and EPA contents were 1500-times and 37-times higher, respectively, than that in commercial poultry feed, indicating that these mixtures could be used as an additive in poultry feed. Statement Of NoveltyThe demand for docosahexaenoic and eicosapentaenoic acids (DHA and EPA) from sh oil has been increasing because of its bene cial use in the aquaculture and food industries but sh oil resources are now becoming unsustainable. Therefore, we have focused on using the heterotrophic microorganism, Aurantiochytrium sp. L3W, to produce DHA and EPA. The present study demonstrated that solid food waste can be used for culturing Aurantiochytrium sp. L3W without sterilization and hydrolysis pretreatments and provided evidence that the strain L3W may utilize solid-state carbon and nitrogen. We obtained biomass mixtures consisting of the remaining food waste and analyzed them for DHA and EPA. The DHA and EPA contents were 1500-times and 37-times higher, respectively, than those in commercial poultry feed. This is the rst report on valorizing solid food waste as a source of PUFAs that are potentially usable as an additive for poultry feed to produce products enriched with PUFAs, such as eggs.