Valorization of brewer's spent grain using fungi solid-state fermentation to enhance nutritional value

Brewer's spent grain (BSG) is a nitrogen and fiber rich waste generated in high volumes in beer manufacturing. Here we have investigated the use of fermentation for value addition to this waste material. In this study we use solid-state fermentation (SSF) using food grade Rhizopus oligosporus to enhance its nutrient content by valorization of BSG. Subsequently, untargeted GC–MS (Gas chromatography mass spectrometry) based metabolomics was used to analyse the constituents. We investigated different solvents to extract extracellular metabolites and best derivatization method, where methanol and silylation provided best results. We observed significant levels of metabolite changes in amino acids, citric acid, vitamins and antioxidants. This data provided insight on metabolites variations during fermentation, proving that fermentation enhanced BSG's nutrient content. Hence, data from metabolomics studies can be used to find novel applications for food wastes and innovative processing methods for valorization of waste materials.