Biocatalysis for rice bran valorization

Rice is the staple food for over half the world's population. As a consequence, rice milling gives rise to a massive amount of waste, namely rice bran (70 kg/ton of rice) and rice husk (200 kg/ton of rice). Although rice bran (RB) is a rich source of fibers (7-11%), highly nutritional proteins (10-16%), lipids (15-22%), carbohydrates (34-52%), and a number of micronutrients, it is currently underutilized. The aim of this work was to exploit the protein and the oil fraction of RB as a source of high-added value products by biocatalysis according to the biorefinery concept. Rice bran proteins (RBP) have a high nutritional value and optimal digestibility and are rich in essential amino acids; last but not least, they are gluten-free and hypoallergenic. However, structural complexity, poor solubility, strong aggregation as well as difficult separation from the other components of the vegetable material make RBP hardly available, thus hampering a possible industrial application. The sequential treatment of RB with carbohydrases and proteases was here used to prepare mixtures of water-soluble peptides (HVP, Hydrolyzed Vegetable Proteins) to be tested as antibacterial, antioxidant and anticholesterol agents, as well as flavour enhancers. To date, activity assays are in progress. Rice bran oil (RBO) represents one of the most underutilized agricultural commodities. Only a limited amount of RBO (<10%) is currently processed into edible oil due to its high free fatty acids (FFA) content. However, a significant number of high-value products require FFA in their manufacturing. We have here investigated the use of RBO as a feedstock for the production of FFA-derived chemicals. To this aim, RBO was submitted to a preparative lipase-catalyzed hydrolysis to obtain pure FFA. Upon process scaling-up and product purification by flash chromatography, FFA were obtained in moderate to good yield. The high acidity of RBO, so far considered as a bottleneck in the exploitation of RBO, has been here turned into an advantage, that is making available FFA mixtures as valuable synthetic precursors.