Hemicellulose content in rice straws of several high-quality rice grains

Abstract

A by-product of rice farming, rice straw is made up of lignin, cellulose, and hemicellulose and comprises lignocellulosic biomass. Particularly rich in this biomass are rice-producing nations like Vietnam, which ranks sixth in the world for rice exports. Because 30-40% of this bioresource is burned to make way for new rice fields for cultivation, its use has not been optimum. Air pollution has been linked to this, particularly in Vietnam. Indeed, burning half of the world’s rice straw produces almost 100 million tons of carbon dioxide emissions. Therefore, to increase the benefits of rice and reduce environmental pollution, lignocellulosic biomass reuse is crucial. This paper reports the hemicellulose content in three rice straw types (OM5451, IR50404, and 6976 commons from An Giang province, Vietnam). Alkaline extraction assisted with ultrasound was employed. In this process, samples were mixed with 2 M sodium hydroxide and ultrasonicated for 30 min at 90^oC. Then, the mixture was continuously heated at 90^oC and stirred at 40 rpm for 1.5 h. Ethanol was used to precipitate hemicellulose. The highest yields obtained of crude hemicellulose were 23.17% in OM5451, 23.1% in IR50404, and 22.94% in 6976 at pH 4.0, however, there was no significant difference at a 95% confidence level as determined by a two-way ANOVA with p-values >0.05. The extracted hemicellulose was confirmed using Fourier- transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermo-gravimetric analysis (TGA).