A Comprehensive Processing of Rice Bran as a Multicomponent Resource

Abstract

A comprehensive liquefaction/disintegration and fractionation of agricultural side streams gives an opportunity to utilize agricultural materials in various applications. Such an approach that simultaneously may reduce land utilization and resources can be helpful to meet sustainability requirements. In this work, the liquefaction and partial fractionation of defatted rice bran was of interest. Relatively simple processes and mild conditions (extraction, membrane separation and hydrothermal disintegration) were investigated. A single step disintegration was also compared to a 3-steps cascade procedure. Apart from cellulose and lignin, almost all rice bran could be transformed into liquid form (~85%). The enzymatic pre-extraction of starch-glucose resulted in a product having ~70% purity which can be increased (>85%) by applying nanofiltration. The protein yield obtained from a 3 steps cascade process at 120 °C and pH 2 was 82% while in the conventional extraction at pH 11.5 only 38% was achieved. The cascade process leads to higher disintegration degree and is helpful to reduce by-products significantly. Nevertheless, it is significantly more water consuming than the single step process. The liquefaction step, including starch/glucose and protein separation, appears not to be the techno-economical limiting factor for the comprehensive utilization of rice bran.