Production of reducing sugars from bagasse and rice husk by acid hydrolysis

Abstract

The agricultural residues bagasse and rice husk can be utilised for the production of reducing sugars through conc. H 2SO 4 hydrolysis. Various process conditions like solid-liquid ratio, particle size, reaction time and concentration of acid have been optimised. To carry out a selective hydrolysis of cellulosic residues, these were delignified by alkali pretreatment prior to hydrolysis. Micro-crystalline cellulose powder was used for comparison. Delignification of agricultural residues improves the yield of reducing sugars. In the present studies, conc. H 2SO 4 was fpund to be a better hydrolytic agent than conc. HCl. An acid concentration of 75% (w/w) with soaking period of 1 h, temperature 50°C, solid-liquid ratio of 1:12, particle size less than 417 microns for primary hydrolysis and heating time of 3 h at 100°C after dilution with 3 volumes of water, were found to be the optimum conditions for the hydrolysis of bagasse and rice husk. Under these conditions, the saccharification attained was 78% and 74·5% for NaOH delignified bagasse and rice husk, and 58% and 49·5% for untreated bagasse and rice husk. Pretreatment of the materials with conc. HCl was found to slightly enhance the yield of reducing sugars in the conc. H 2SO 4 hydrolysis.