Rice husk integrated biochemical refinery for the production of nano- and bioproducts

Abstract

Rice husk contains high contents of cellulose, lignin, and inorganic compounds, which can be recovered and utilized in a variety of useful applications. In this study, rice husk was refined using a multistage process for producing nano- and bioproducts. To begin, the material was treated with dilute sulfuric acid for obtaining a pentose solution, which was then used for Candida utilis yeast fermentation. In the next stage, the pre-hydrolyzed rice husk was treated with an alkaline solution under regular pulping conditions to break down all chemical bonds between the substances in the material. Subsequently, cellulose was extracted for nanocellulose production, while lignin and silica were isolated via acid precipitation. Proper conditions for these processes were established. Under suitable conditions, about 55.0% of the rice husk was effectively utilized. Over 75.0% of the rice husk pentosan was converted into xylose and arabinose for single-cell protein fermentation. Lignin was mostly transformed into lower molecular weight compounds or single substances, resulting in a recovery rate of about 17.0%. The precipitation’s pH for silica and lignin recovery was 8.5 and 3.0, respectively. The findings of this work provide an effective solution for the utilization of agricultural residue and contribute significantly to the sustainable development.