Browsing by Author "Autio, Tuomo"

Cereal side streams, such as rice bran and dried distiller´s grain with solubles (DDGS) are formed in large quantities in industrial processes. These side streams contain considerable amounts of protein that could be better valorized. Deep eutectic solvents (DES) have been applied in various biomass fractionation studies and could be potentially used as protein extraction solvents. The literature review of this master´s thesis covered the characteristics of rice bran and DDGS, existing extraction methods and DESs. The aim of this work was to study the effect of water content of two DESs (choline chloride:urea, molar ratio 1:2 and sodium acetate:urea, 1:2) on the protein extraction from rice bran and DDGS. Protein extraction yield, protein content in dialyzed and freeze-dried extracts and protein fragmentation were studied. DDGS protein extraction yields with ChCl:urea at 30-50% water contents (56-57%) were significantly higher (p<0.05) than by NaOH (46%) and water (36%), which were used as reference solvents. With NaAcO:urea the water content did not affect the yields significantly and the yields did not differ from those of the reference solvents. In case of rice bran, a low water content produced higher yields and with NaAcO:urea at a water content of 10% the yield was 70%, which was significantly higher than with the reference solvents. Protein contents were measured by two methods, which gave conflicting results. According to BCA assay, the highest protein concentration from DDGS was obtained with NaOH, but according to elemental analysis with the DESs. In case of rice bran, the protein concentrations were extremely low with both methods. Based on these results, rice bran protein extraction using DESs does not appear feasible, whereas DDGS protein could be extracted more efficiently using the DESs than the reference solvents. Neither of the DESs at any water contents degraded protein to a significant extent.