Continuous oscillatory flow as process intensification strategy in protein extraction from brewer's spent grain

A continuous oscillatory flow bioreactor (COFB) set-up was designed, constructed and evaluated for a biorefining application. Protein solubilisation was carried out in the COFB with brewer's spent grain (BSG) as substrate at high solid loading and without pre-treatment. The process objective was to proof the feasibility of COFBs as reactor technology for direct conversion of BSG in a simple but efficient continuous process prior to subsequent anaerobic digestion. The characterization of the overall process performance was measured via the achieved protein concentration at the reactor's outlet. Protein yields of 40–90 % throughout all tested operating conditions were achieved, which corresponded to protein hydrolysate concentrations of 16–39 mg_protein/ml. Thereby, most abundant amino acids found were glutamic acid, leucine, aspartic acid, phenylalanine and valine. Residual solids after protein extraction were treated in anaerobic digestion and the biomethane potential (BMP) was determined. Untreated BSG and hydrolysed BSG resulted in similar biogas yields per organic dry matter in the range of 376 – 422 [Nm³/to_VS].