Solid-state fermented brewer's spent grain enzymatic extract increases in vitro and in vivo feed digestibility in European seabass

Abstract

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.

Application of Fermented Brewer’s Spent Grain Extract in Plant-Based Diets Improves Pre- and Post-mortem Oxidative Status of European Seabass (Dicentrarchus labrax)

“…Previously, it was observed that the BSG-extract increased cellulose and hemicellulose digestibility [31], which may also have contributed to the reduction of the oxidative intestine damage of European seabass since the dietary complex carbohydrates negatively impact fish intestine oxidative status. Moreover, by disrupting cell walls through enzymes action, embedded phenolic compounds may also become available, thus enhancing their direct antioxidant action.…”

“…The observed role of BSG-extract in increasing NSP digestibility (see [31]) may also have modulated the activity of hepatic antioxidant enzymes. The effect of dietary supplementation with exogenous enzymes on liver oxidative stress has been evaluated with variable results.…”

“…Previously, it was shown that SSF of BSG with Aspergillus ibericus led to the production of an extract rich in carbohydrases, with high activity and thermostability, and high antioxidant activity [30]. Supplementation of a practical diet with this extract increased energy and cellulose digestibility [31] and improved feed utilization efficiency of European seabass (Dicentrarchus labrax) [32]. The present study aimed to evaluate the effect of dietary supplementation with this extract on the pre-and postmortem oxidative status of European seabass.…”

The Potential of Brewer’s Spent Grain in the Circular Bioeconomy: State of the Art and Future Perspectives

“…Solid-state fermentation (SSF) technology is a promising technology for the treatment of lignocellulosic materials for various applications (Tišma et al, 2021b). Xylanase pretreatment BSG for chicken feed reduced the reduced the concentration of polymeric arabinose and xylose by 15%-30% (Denstadli et al, 2010), and the inclusion of BSG treated with SSF by Aspergillus ibericus in fish diet increased dry matter digestibility and energy (Fernandes et al, 2021). SSF was used for BSG treatment for the production of food, wherein the properties of whole-wheat bread with the addition of fermented BSG by Aspergillus awamory increase the amount of ferulic acid by 198% (Dos Santos Costa et al, 2020).…”

Solid-State Hydrolysis (SSH) Improves the Nutritional Value of Plant Ingredients in the Diet of Mugil cephalus

“…The efficiency of hydrolysis produced by such enzymes is greatly conditioned by several aspects. As an example, there may be interactions between gastric and intestinal proteases produced by fish and the exogenous enzymes that can negatively affect their potential beneficial effects [14]. Furthermore, the effectiveness of the exogenous enzymes may be greatly reduced by the high temperatures reached during feed preparation or, in the case of being applied post-extrusion via oil top coating or spraying, by the time available for the enzymatic action inside the digestive system of the species, which is closely related to gut transit rates linked to water temperature.…”