Assessment of Bioprocessed Post-Consumer Food Waste as Feed for Nile tilapia (Oreochromis niloticus)

Abstract

Fed aquaculture depends on a ready availability of affordable and nutritious proteins and essential lipids, especially the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Consequently, aquaculture is a fast-growing food industry capable of meeting the demand for nutritious food only if the burdening production expenses, to which aquafeed accounts for the major part, are decreased. Food waste (FW) is a sustainable and economical source of nutrients that could replace part of fish feed ingredients and decrease aquafeed cost. Nevertheless, prior to utilization as feed ingredient, FW necessitates processing to adjust its nutritional composition to meet animal needs and consumer preferences. Bioprocessing FW using microbial cells or microbial enzymes is an economical and environmentally friendly method to improve FW composition.

A preliminary study was performed to assess the effect of bioprocessing FW by Saccharomyces cerevisiae, Trichoderma virens and Aspergillus niger on protein, and EPA and DHA content. Results of the study indicated that both filamentous fungi failed to bio-convert fatty acids into EPA and DHA, but baker’s yeast successfully increased the protein content of oil-extracted FW by 15.3%. Accordingly, the present study assessed the potential benefits of substituting part of juvenile Nile tilapia (Oreochromis niloticus) diets with yeast-fermented FW (FWY). Seven isonitrogenous diets (34% crude protein) were prepared, with FWY substituting 0, 15, 20, 25, 30, 35, and 40% of the feed mix. Juvenile O.niloticus (11.070.01 g) were size sorted and stocked into 21 tanks. Each diet was randomly assigned to three replicate tanks, and the feeding trial was performed for 6 weeks.

Results suggest that up to 30% of Nile tilapia feed can be substituted with FWY without significant effect on final body weights and lengths, feed conversion ratio, specific growth rate, hepatosomatic and viscerosomatic indices, body moisture, protein, and lipid content of fish offered the various diets. Formulating Nile tilapia feed with up to 30% yeast-fermented food waste is one of several promising solutions to increasing demand for protein rich food. Aquaculture production costs will be greatly reduced, which will be reflected in enhanced sustainable food security.