Mohamed Abdulkadir Gedi

Currently, there is an urgent need for the growing aquaculture sector to rely on sustainable ingredients which can achieve optimal growth while maintaining fish’s nutritional value (especially omega-3 fatty acid content) for human consumption. Here, C. reinhardtii biomass was substituted for fishmeal in zebrafish (Danio rerio) diets in wild-type and mutant (Casper) strains. Four isonitrogenous (46% cp), isocaloric (19–21 MJ/kg DW) diets were prepared with C. reinhardtii replacing 10% (C10), 20% (C20), and 50% (C50) of the fishmeal component of the diet formulation. Over 8 weeks of feeding trials, the zebrafish showed a significant growth improvement when fed C10, C20, and C50 compared with the control (no C. reinhardtii), with C20 giving the best performance in terms of growth, feed conversion ratio (FCR), and specific growth rate (SGR). Interestingly, C. reinhardtii in the diet increased the levels of linolenic acid (C18:3 n-3) and hexadecatrienoic acid (C16: 4-n-3) (p ≤ 0.05) in the zebrafish. Yellow pigmentation, which was shown to be lutein, was observed in eggs and zebrafish flesh for fish fed a diet containing C. reinhardtii. Moreover, the zebrafish assimilated β-carotene from C. reinhardtii and converted it to vitamin A. Overall, while replacing 20% of fishmen in the zebrafish’s diet with C. reinhardtii biomass offers the best results, replacement with only 10% showed a significant benefit for the zebrafish. Furthermore, replacing fishmeal with 50% C. reinhardtii is still possible and beneficial, and C. reinhardtii whole cells are digestible by zebrafish, thus demonstrating that C. reinhardtii not only has the potential to serve as a feed supplement but that it can also act as a feed substitute once the production cost of microalgae becomes competitive.

The lipophilic nutrients in a chloroplast-rich fraction derived from pea vine postharvest field-residue are released in an in vitro digestion model; the extent of their release (bioaccessibility) is affected by heat-treatment of biomass or juice.

Chlamydomonas reinhardtii is a green microalgae used as a model organism associated with biotechnological applications, yet its nutritional value has not been assessed. This study investigates the nutritional capacity of C. reinhardtii as an additional value for this species beyond its known potential in biofuels and bio-products production. The composition of key nutrients in C. reinhardtii was compared with Chlorella and Spirulina, the species widely regarded as a superfood. The results revealed that the protein content of C. reinhardtii (46.9%) was comparable with that of Chlorella (45.3) and Spirulina (50.4%) on a dry weight basis. C. reinhardtii contained all the essential amino acids with good scores based on FAO/WHO values (0.9–1.9) as in Chlorella and Spirulina. Unsaturated fatty acids predominated the total fatty acids profile of C. reinhardtii were ~74 of which ~48% are n-3 fatty acids. Alpha-linolenic acid (ALA) content in C. reinhardtii (42.4%) was significantly higher than that of Chlorella (23.4) and Spirulina (0.12%). For minerals, Spirulina was rich in iron (3.73 mg/g DW) followed by Chlorella (1.34 mg/g DW) and C. reinhardtii (0.96 mg/g DW). C. reinhardtii, unlike the other two species, consisted of selenium (10 µg/g DW), and had a remarkably lower heavy metal load. Moreover, C. reinhardtii contained relatively high concentrations of chlorophyll (a + b) and total carotenoids (28.6 mg/g DW and 6.9 mg/g DW, respectively) compared with Chlorella (12.0 mg/g DW and 1.8 mg/g DW, respectively) and Spirulina (8.6 mg/g DW and 0.8 mg/g DW, respectively). This study confirms that, based on its nutrient credentials, C. reinhardtii has great potential as a new superfood or ingredient for a food supplement.

Galactolipases allow the digestion of galactolipids, the most abundant lipids on Earth and the main source of α-linolenic acid.

In this chapter we introduce the concepts of upcycling and valorisation of food waste by highlighting some work at the University of Nottingham looking at valorisation of feed-stocks from brewers’ spent grain, Citrus waste, Pea Haulm and Bran, producing value-added products spanning macronutrients: fibre and protein, and lipids (chloroplast-rich fractions and waxes), as well as identifying carry over of micronutrients, as a result of careful and sustainable processing. The functionalised materials provide novel structuring capability and also nutritional benefits. Finally, a case study is presented turning food by-products into functionalised food ingredients that have been used to produce safe ingredients and final products with higher dietary fibre content, where products were well accepted in initial sensory tests, providing waste reduction and lower carbon emissions across the supply chain.

Increasing global aquaculture production, is putting pressure on fishmeal and fish oil supply. There is therefore a growing search for more sustainable sources of proteins and polyunsaturated fatty acids as fish feed ingredients. Chloroplasts are the organelles in the leaves of plants where many of the valuable nutrients, fatty acids (FAs), amino acids, vitamins and pigments, are synthesised. Chloroplasts could be incorporated into fish diets either retained in, or liberated from, plant cells. In this study zebrafish were fed with seven different diets individually; fish were fed with diets reducing fishmeal levels (10, 20 or 50%) using either spinach leaf powder (SLP) or a chloroplast rich fraction (CRF) prepared by an established method to recover chloroplasts. Both SLP and CRF had a positive impact on the growth, taste response, whole fish FA composition, and carotenoid profile. Fish fed with CRF diets showed significantly (P ≤ 0.05) greater α-linolenic (C18:3 n-3) and hexadecatrienoic (C16:3) acid contents than those of SLP and the control. Hexadecanoic acid (C16:3) is a unique FA in the galactolipids of the chloroplast; its presence in zebrafish tissues proves that zebrafish digest and absorb chloroplast galactolipids. The lutein profile of eggs produced by zebrafish fed with the CRF diet was significantly (P ≤ 0.05) higher than those of SLP and the control. Alterations in egg colour were also noted, warranting further investigations of the diet impact on fish fecundity, embryo fertility, hatch rate and larval survival.