Chemical composition and monolignin in alkali and acid treated corncob affect sugar release

In order to understand how do chemical composition and monolignin in corncob material affect biomass digestion, the effect of alkali(NaOH), acid(H2SO4) pretreatment condition and the combined severity factors (CSF) on the chemical composition and monolignin content in corncob, and the effect of chemical composition and lignin monomers content in the pretreated corncob on sugar release were comparably investigated. In NaOH and H2SO4 system, lignin and hemicellulose content decreased to almost zero at combined severity factor (CSF) 9.5 and 10.5, respectively. 5 mol/L NaOH followed by enzymatic hydrolysis for 72 h could give rise to 84.62% reducing sugar yield, which was 2.02 times higher than that treated by H2SO4. A negative correlation was found between lignin, hemicellulose and sugar release upon alkali and acid pretreatment, respectively. Evaluation of monolignin in corncob samples suggested that higher S/G ratio or removal of H-monomer was favorable to sugar release in both alkali and acid system. Thus, corncob substrates with lower lignin and hemicellulose content and higher S/G ratio may be conducive to enzymatic digestibility of biomass.