Brewers’ Spent Yeast and Grain Protein Hydrolysates as Second-Generation Feedstuff for Aquaculture Feed

Abstract

Aquafeeds are formulated to contain all the essential nutrients that fishes need to keep healthy. They are highly dependent on marine ingredients: fish meal and oil. Hence, alternative ingredients which successfully replace these marine ingredients are required to result in sustainable and economical feeds. In this context, brewers' spent grain and yeast arise as alternative potential ingredients for aquafeed due their availability and nutritional content. However, reducing aquaculture's dependence on marine resources depends not only on developing alternative ingredients but also on improving their feed efficiencies.In this context, Life Brewery project (LIFE16ENV/ES/000160) proposes an enzymatical hydrolysis step prior to the stabilization process to improve the digestibility of brewers' by-products and, therefore, increases the assimilation of nutrients by fishes. Hence, optimum hydrolysis conditions for both brewers' spent grain and yeast have been defined by comparing different enzymes combination and hydrolysis conditions at laboratory scale. Afterwards, selected enzymes and conditions have been validated at industrial scale. Finally, the digestibility of different experimental diets containing both hydrolysed and un-hydrolysed ingredients from brewers' waste has been determined with positive results.Based on obtained results, it can be concluded that both hydrolysed and un-hydrolysed brewers' spent grain and yeast are suitable as alternative ingredients which successfully replace marine ingredients. Nevertheless, hydrolysis step improves ingredients efficiency and involves higher digestibility than un-hydrolysed ingredients.

Characteristics of the Proteolytic Enzymes Produced by Lactic Acid Bacteria

“…It should be noted that a uniform protein distribution is not desirable, as the foamy beer is reduced and becomes “empty” in taste. On the other hand, insufficient protein distribution makes filtering more difficult and causes beer to become cloudy during storage [ 33 , 117 , 118 , 119 , 120 , 121 , 122 ].…”

Brewer’s Spent Grains—Valuable Beer Industry By-Product

“…Moreover, nutritional quality tests led by Nazzaro et al showed that brewer’s by-products might be suitable for marine ( Sparus aurata ) and fresh ( Oncorhyncus mykiss ) fish nutrition, with digestibility up to 88% for both fish species [ 123 ]. Another approach for utilization of BSG is enzymatic pre-treatment of mentioned by-product in order to cleave remaining cellulose and protein chains [ 124 ].…”

Barley Protein Properties, Extraction and Applications, with a Focus on Brewers’ Spent Grain Protein

“…In addition to this, large volumes of by-product are produced at nearly every step of the process including spent grain, spent yeast, wastewater and spent hops, among others. The brewing industry is responsible for a huge volume of waste with ~10,000 tonnes of liquid waste and 137–173 tonnes of solid waste produced per 1000 tonnes of beer [ 2 ], so the potential valorisation of these waste products is of great economic interest. Due to its high nutritional value, particularly in terms of high-quality protein, the application of BSG proteins in human nutrition is of particular interest.…”

“…The addition of BSG has already been examined in breads, biscuits and other bakery products as well snack-type products. In addition to this, applications of BSG include use in animal feed formulation for a range of species [ 1 , 2 , 3 , 4 ] as well as use as a potential substrate for other industrial processes, namely biogas production, polysaccharide extraction and phenolic compound isolation [ 4 , 5 , 6 ].…”