Aquafeed Production from Fermented Fish Waste and Lemon Peel

Abstract

In order to obtain a high-protein-content supplement for aquaculture feeds, rich in healthy microorganisms, in this study, Saccharomyces cerevisiae American Type Culture Collection (ATCC) 4126 and Lactobacillus reuteri ATCC 53608 strains were used as starters for fermenting fish waste supplemented with lemon peel as a prebiotic source and filler. Fermentation tests were carried out for 120 h until no further growth of the selected microorganisms was observed and the pH value became stable. All the samples were tested for proteins, crude lipids, and ash determination, and submitted for fatty acid analysis. Moreover, microbiological analyses for coliform bacteria identification were carried out. At the end of the fermentation period, the substrate reached a concentration in protein and in crude lipids of 48.55 ± 1.15% and 15.25 ± 0.80%, respectively, representing adequate levels for the resulting aquafeed, whereas the ash percentage was 0.66 ± 0.03. The main fatty acids detected were palmitic, oleic, and linoleic acids. Saturated fatty acids concentration was not affected by the fermentation process, whereas monounsaturated and polyunsaturated ones showed an opposite trend, increasing and decreasing, respectively, during the process. Coliform bacteria were not detected in the media at the end of the fermentation, whereas the amount of S. cerevisiae and L. reuteri were around 1011 and 1012 cells per g, respectively.

Single Cell Protein Production through Multi Food-Waste Substrate Fermentation

“…The mixture was allowed to stand overnight and the lower lipid layer, transferred into a pretreated and weighed flask, was dried off. The difference in the two weights gave the weight of the fat [16].…”

“…This decrease can be ascribed to the autolysis phenomena due to the yeast cells deaths during the decline phase of the growth curve [55,56]. The protein percentage increased during the substrate fermentation by the yeast, allowing the obtainment of a substrate enriched in protein, having a suitable percentage for aquafeed [16,22] and for feed [30,57]. Moreover, comparing these results with previous studies where the fermentation medium was represented by a single variety of waste per time, it is possible to notice that a higher percentage of protein was reached using a multi complex medium.…”

“…From a chemical point of view, food waste is mainly composed by carbohydrate polymers such as starch, proteins, lipids, cellulose, and other microelements [7][8][9][10]. Due to this composition, it is classified as a low cost, high potency second generation feedstock [1], and usable as a substrate for microbial fermentation for bioconversion into value added products, such as enzymes, feed additives, biofuels, animal feeds as well as other useful chemicals or products, food grade pigments, and single cell protein (SCP), enhancing food security and environmentally sustainable development [11][12][13][14][15][16][17][18][19][20][21].…”

“…Previous studies refer to SCP production via fermentation by testing a single kind of food processing or agricultural waste each time, such as wheat bran [28], orange and lemon peel [29,30] banana peel [31,32], fish waste [16], pineapple waste [23,24], whey [33] and others.…”

“…The yeast Saccharomyces cerevisiae is widely accepted, considering its use in traditional fermentation and its nutritional quality [22]. Moreover, due to its immunostimulating compounds, such as nucleic acid, b-glucans and mannan oligosaccharides [40,41], it has been used, e.g., for aquafeed production by fish waste fermentation, after medium supplementation with lemon peel used as natural filler [16] for reducing natural liquefaction occurring during fish waste fermentation. This study has evaluated the possibility of using a multicomplex substrate, made up of fish waste and different agricultural wastes, to set up a fermentation process, carried out by Saccharomyces cerevisiae ATCC 36858, which allows the simultaneous biovalorization of different food wastes without the necessity to separate the waste coming out from food process to obtain a single cell protein suitable as feed.…”