Department of Biology, Faculty of Sciences of University of Oporto (FCUP), Porto, Portugal.
Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), Matosinhos, Portugal.
Sci Rep. 2021 Nov 25;11(1):22946. doi: 10.1038/s41598-021-02393-x.
Brewer's spent grain (BSG) is the largest by-product originated from the brewery industry with a high potential for producing carbohydrases by solid-state fermentation. This work aimed to test the efficacy of a carbohydrases-rich extract produced from solid-state fermentation of BSG, to enhance the digestibility of a plant-based diet for European seabass (Dicentrarchus labrax). First, BSG was fermented with A. ibericus to obtain an aqueous lyophilized extract (SSF-BSG extract) and incorporated in a plant-based diet at increasing levels (0-control; 0.1%, 0.2%, and 0.4%). Another diet incorporating a commercial carbohydrases-complex (0.04%; Natugrain; BASF) was formulated. Then, all diets were tested in in vitro and in vivo digestibility assays. In vitro assays, simulating stomach and intestine digestion in European seabass, assessed dietary phosphorus, phytate phosphorus, carbohydrates, and protein hydrolysis, as well as interactive effects between fish enzymes and dietary SSF-BSG extract. After, an in vivo assay was carried out with European seabass juveniles fed selected diets (0-control; 0.1%, and 0.4%). In vitro digestibility assays showed that pentoses release increased 45% with 0.4% SSF-BSG extract and 25% with Natugrain supplemented diets, while amino acids release was not affected. A negative interaction between endogenous fish enzymes and SSF-BSG extract was observed in both diets. The in vivo digestibility assay corroborated in vitro data. Accordingly, the dietary supplementation with 0.4% SSF-BSG increased the digestibility of dry matter, starch, cellulose, glucans, and energy and did not affect protein digestibility. The present work showed the high potential of BSG to produce an added-value functional supplement with high carbohydrases activity and its potential contribution to the circular economy by improving the nutritional value of low-cost and sustainable ingredients that can be included in aquafeeds.
啤酒糟（BSG）是啤酒厂产生的最大副产物，具有通过固态发酵生产碳水化合物酶的巨大潜力。本研究旨在测试来源于啤酒糟固态发酵的富含碳水化合物酶的提取物的功效，以提高植物性饲料对欧洲鲈鱼（Dicentrarchus labrax）的消化率。首先，将 A. ibericus 发酵啤酒糟以获得水冷冻干燥提取物（SSF-BSG 提取物），并将其以不同水平（0-对照组；0.1%、0.2%和 0.4%）添加到植物性饲料中。另一种包含商业碳水化合物酶复合物（0.04%；Natugrain；BASF）的饲料也进行了配制。然后，在体外和体内消化率测定中对所有饲料进行了测试。在体外消化率测定中，模拟了欧洲鲈鱼的胃和肠道消化，评估了饲料中的磷、植酸磷、碳水化合物和蛋白质水解，以及鱼酶和饲料 SSF-BSG 提取物之间的相互作用。然后，用欧洲鲈鱼幼鱼进行了体内消化率测定，幼鱼喂食了选择的饲料（0-对照组；0.1%和 0.4%）。体外消化率测定表明，添加 0.4% SSF-BSG 提取物和添加 Natugrain 可使戊糖释放增加 45%和 25%，而氨基酸释放不受影响。在两种饲料中均观察到内源性鱼酶与 SSF-BSG 提取物之间存在负相互作用。体内消化率测定结果与体外数据一致。因此，在饲料中添加 0.4% SSF-BSG 提高了干物质、淀粉、纤维素、葡聚糖和能量的消化率，而不影响蛋白质消化率。本研究表明，BSG 具有生产高碳水化合物酶活性的高附加值功能性补充剂的巨大潜力，并通过提高低成本和可持续成分的营养价值，为循环经济做出贡献，这些成分可被纳入水产饲料。
