Contemporary issues in fisheries and aquaculture: a review on non – conventional feed ingredients for fish feed in Nigeria

In Africa, Nigeria offers the largest market for fisheries products. Fish culture is gaining importance in Nigeria as locally available raw materials such as yam, plantain, banana, cowpeas, mucuna, maize, cassava, millet, sorghum, groundnut, sunhemp seed and brewery wastes are considered as potential materials for fish feed. Non–conventional feeds are locally available feedstuff which are not standardized and the usage is not widely-spread. In most cases, they are not consumed by man. Sadly, Nigerian economy had depended on imported feedstuffs to supplement the domestic conventional feedstuffs, however, the country is currently looking into a way of improving local feedstuffs production to minimize importation. In Fisheries and Aquaculture, there are many contemporary issues but this paper focuses on the use of non–conventional feed ingredients like Typha flour in fish feed. Several parts of Typha are edible including the rhizome. Research has shown that the plant is rich in energy, carbohydrates, sugars, dietary fiber, protein, vitamins, minerals and water. The competition for the conventional feed ingredients for human and animal consumption has resulted in significant price escalations hence the need for on-going research on alternativeingredients for use in aquafeed. Thus, great attention is given to the production of effective and cheap feed that will benefit fish farmers in Africa because fish feed is very important. Despite the fact that several studies have been done in Nigeria to replace fishmeal with other proteins of plant & animal origin but the results have been range from poor to very good in terms of fish growth and fish conversion efficiency.

Circular economy in the brewing chain

The main aim of this review was to check for the applicability of the concept of circular economy to brewing chain. By analyzing the beer brewing process, it was possible to identify the main brewery wastes formed and packaging materials used as well as their range of composition and yields. In order to reduce the contribution of packaging material to the carbon footprint of beer, it would be necessary to replace one-way containers used nowadays with lighter, reusable, or recycled ones. Even if the contribution of beer consumption phase was taken into account, there was no definitive solution about the less environmentally impacting beer packaging format. The direct management of polyethylene terephthalate (PET) packaging for liquid foodstuffs could make available 100% recycled PET flakes to be reconverted into food-grade bottles with minimum downcycling to other non-food usage. The countless potential uses of brewery wastes in nutritional and biotechnological fields were tested in laboratory by disregarding any cost–benefit or market analysis. This was mainly because the estimated market price of dried brewer’s spent grain (BSG) resulted to be about 450% higher than that of conventional lignocellulose residues. All the alternative uses hailed in the literature appeared to be more useful for publishing articles than for defining any economically feasible reusing procedure for all brewery wastes. Owing to their high moisture content, such wastes are so perishable as to prevent their safe usage in the human food chain. Currently, their use as-is in animal feeding is the disposal method not only economically feasible but also able to reduce the greenhouse gas load of beer packed in glass bottles (GB) by about one-third of that associated with packaging materials. Not by chance, it is practiced by most industrial and craft breweries.

Valorization of Brewery Wastes for the Synthesis of Silver Nanocomposites Containing Orthophosphate

Brewery wastes from stage 5 (Wort precipitate: BW5) and stage 7 (Brewer’s spent yeast: BW7) were valorized for the synthesis of silver phosphate nanocomposites. Nanoparticles were synthesized by converting silver salt in the presence of brewery wastes at different temperatures (25, 50, and 80 °C) and times (10, 30, and 120 min). Unexpectedly, BW7 yielded Ag3PO4 nanoparticles with minor contents of AgCl and Ag metal (Agmet). Contrastingly, BW5 produced AgCl nanoparticles with minor amounts of Ag3PO4 and Agmet. Nanocomposites with different component ratios were obtained by simply varying the synthesis temperature and time. The morphology of the nanocomposites contained ball-like structures representative of Ag3PO4 and stacked layers and fused particles representing AgCl and Agmet. The capping on the nanoparticles contained organic groups from the brewery by-products, and the surface overlayer had a rich chemical composition. The organic overlayers on BW7 nanocomposites were thinner than those on BW5 nanocomposites. Notably, the nanocomposites exhibited high antibacterial activity against Escherichia coli ATCC 25922. The antibacterial activity was higher for BW7 nanocomposites due to a larger silver phosphate content in the composition and a thin organic overlayer. The growth of Agmet in the structure adversely affected the antimicrobial property of the nanocomposites.

Brewery’s waste streams as a valuable substrate for Black Soldier Fly Hermetia illucens (Diptera: Stratiomyidae)

The growing population and, consequently, the demand for food, has led to an increase in the agro-food activities, causing irreversible exploitation of natural resources. The use of insects for the management and recycling of by-products of the agro-food industry and for the production of proteins is growing. The Diptera Hermetia illucens is of particular interest as larvae are able to grow rapidly on numerous organic matters and are rich in proteins and fats. The identification of a low-cost and low-impact substrate suitable for the mass rearing of H. illucens is consequently of great interest. In this study, we evaluated the suitability of brewery wastes, spent grain and trub (used separately or mixed), as rearing substrate for the larvae. We evaluated the effect of these diets on preimmaginal performance (survival, developmental time, and weight reached) and adult traits (sex-ratio, dimension, and female fertility). As a result, the different substrates significantly impacted different biological traits. Best results, both for larvae and adults, were reported when the brewery wastes were provided together, leading to similar results obtained in a control diet and comparable to other previous studies. We conclude that brewery by-products can be valuable substrate for larval growth and in this way can be efficiently recycled and valorised.