The byproduct-organic acids strengthened pretreatment of cassava straw: Optimization and kinetic study

The subcritical liquid hot water (SLHW) pretreatment could be strengthened by its byproduct-organic acids, such as acetic acid (AA), lactic acid (LA) and formic acid (FA). The effects of these three acids on the pretreatment were investigated by the yield of fermentable sugars. The results showed that the addition of acids could effectively catalyze the hydrolysis of hemicellulose to C5 sugars and contribute to the subsequent enzymatic hydrolysis of cellulose. It was found that all three organic acids promote xylose production, and the copresence of AA + LA could limit the content of the fermentation inhibitor. The optimum proportion of three organic acids were 0.33 wt%AA + 0.45 wt%LA + 0.20 wt%FA, and the yield of C5 sugars after pretreatment and C6 sugar after enzymatic hydrolysis were 89.06% and 78.56%, respectively. The kinetic studies proved that byproduct-organic acids could promote xylose production and inhibit its further degradation and explained that xylose would accumulate at lower temperatures.