Thesis (Ph.D.)--Chulalongkorn University, 2011

Subcritical and supercritical fluid extractions have been developed in order to recover valuable compounds from lignocellulosic biomass. In this work, the authors focused on γ-oryzanol and proteins extraction from rice bran and de-oiled rice bran which are generally used as an animal feed. The experimental results showed that supercritical carbon dioxide (SC-CO₂) could be used to extract rice bran oil with relatively high γ-oryzanol concentration whilst subcritical water (SW) could recover 100% of protein. The kinetic information of rice bran protein hydrolysis under SW atmosphere indicated that proteins/polypeptides hydrolyze to amino acids within two pathways. Moreover, the increase in temperature and reaction time (over 200 ℃ and 30 min) favored the proteins/polypeptides degradation rate. Thus, the extraction condition for SW extraction should be optimized or the amino acid production would be focused instead. Finally, the multi-fluid processing or consecutive extraction process using SC-CO₂followed by SW was investigated. The suitable condition obtained from each single-fluid extraction was used. The results showed that SC-CO₂ extraction and SW extraction could be operated sequentially without any interaction. The obtained products were not only rice bran oil with high concentrated γ-oryzanol and proteins, but also sugars, amino acids and other value-added products.