Improvement of the Nutraceutical Profile of Brewer’s Spent Grain after Treatment with Trametes versicolor

Abstract

Brewer’s spent grain (BSG) is an important secondary raw material that provides a readily available natural source of nutraceuticals. It finds its largest application as animal feed and part of the human diet, while the future perspective predicts an application in the production of value-added products. In order to investigate a sustainable BSG treatment method, two BSG samples (BSG1 and BSG2) were evaluated as substrates for the production of hydrolytic (xylanase, β-glucosidase and cellulase) and lignolytic enzymes (laccase, manganese peroxidase and lignin peroxidase) by solid-state fermentation (SSF) with Trametes versicolor while improving BSG nutritional value. The biological treatment was successful for the production of all hydrolytic enzymes and laccase and manganese peroxidase, while it was unsuccessful for the production of lignin peroxidase. Because the two BSGs were chemically different, the Trametes versicolor enzymes were synthesized at different fermentation times and had different activities. Consequently, the chemical composition of the two BSG samples at the end of fermentation was also different. The biological treatment had a positive effect on the increase in protein content, ash content, polyphenolic compounds, and sugars in BSG1. In BSG2, there was a decrease in the content of reducing sugars. Cellulose, hemicellulose, and lignin were degraded in BSG1, whereas only cellulose was degraded in BSG2, and the content of hemicellulose and lignin increased. The fat content decreased in both samples. The safety-related correctness analysis showed that the biologically treated sample did not contain any harmful components and was therefore safe for use in nutritionally enriched animal feed.

Bioconversion of Grape Pomace with Rhizopus oryzae under Solid-State Conditions: Changes in the Chemical Composition and Profile of Phenolic Compounds

“…Animals exposed to PAHs experience disorders of the immune system, urinary system, body fluids, and skin and lung damage. In studies of feed mixtures for pigs and cows, PAHs were detected at concentrations of 0.082 and 0.128 mg/kg [61], while in a study published by Zeko-Pivač et al [5], they were <0.020 mg/kg LOQ for raw and fermented brewers spent grain. According to EU DIRECTIVE 2002/32/ EC [60], the maximum allowed concentration of aflatoxin in animal feed is 0.02 mg/kg.…”

“…The preparation of animal feed requires the presence of certain minerals necessary for animal health and productivity, and numerous trace elements are added to animal feed as additives. Some elements, such as As, Cd, F, Pb, and Hg, are considered undesirable if they exceed the prescribed permissible concentrations [5]. Table 3 shows the results of minerals and heavy metals detected in GP before and after 15 days of SSF by R. oryzae.…”

“…Grape pomace (GP) is generally considered as waste, and its disposal is a major challenge for wineries. As a raw material, GP has been the subject of numerous studies, especially in the field of production of high-value products, such as polyphenols [1,2], organic acids [3], enzymes [4,5], GP extracts with improved antioxidant and prebiotic activity [6], application to fertilizer production [7], and others [8]. The high content of lignocellulosic components in GP requires the development of biorefinery approaches aimed at recycling GP and separating some high-value products, such as polyphenols.…”

“…In order to break the complex lignocellulosic structure, release some bioactive compounds, and improve the nutritional properties of biomass, such as GP, different pretreatment methods (chemical, physical, biological) are used, with biological processes having advantages because they are efficient, cost-effective, and environmentally friendly [9,10]. Since the abovementioned properties are characteristic of solid-state fermentation (SSF), this biological treatment is often used as a pretreatment method for lignocellulosic biomass [5,[10][11][12]. SSF involves different microorganisms that produce a complex enzyme system during growth that is responsible for breaking down complex molecules into simpler ones and releasing them from the lignocellulosic structure [11].…”

“…Moreover, SSF is a sustainable process that has the potential to recover bioactive phenolic compounds and valorize waste materials, such as pineapple waste, wheat bran, brewer's grains, etc. [5,11,12]. Valorized material with enhanced nutritional properties has the potential to be used as animal feed [10,13].…”