Inter‐relationships between acidic and alkali treatments of cotton straw and wheat straw and their fibre chemical properties

Abstract

AbstractThe amount of lignin in the cell walls of cotton straw (CS) and wheat straw (WS) was found to be the same, but the ratio between lignin and hemicellulose was considerably lower in CS than in WS. In CS the amount of soluble acid lignin was less than 1% of the total lignin, whereas in WS it was 20%.The amount of phenolics in concentrated sulphuric acid (72%) hydrolysates of the cell wall was reduced drastically in WS compared with the amount released by diluted (1 N) sulphuric acid; this may have been due to polymerisation of low‐molecular‐size lignin.The amount of alkali‐soluble lignin in WS was 3–7 times greater than in CS. Following acid treatment the amount of alkali‐soluble lignin was reduced from 20% of the total content to 5% in WS, and from 5% to 1% in CS.Enzymic hydrolysis was 49% higher in WS cell wall than in CS cell wall. In WS, acidic and alkali pretreatments followed by cellulase treatment increased glucose yield from cellulose by 260% and 280%, respectively. In CS, acidic pretreatment did not affect the glucose yield from cellulose, whereas alkali treatment increased it by 35%.