Pseudo-lignin Retarded Bioconversion of Sugarcane Bagasse Holocellulose after Liquid Hot Water and Acid Pretreatments

Pseudo-lignin derived from the condensation of carbohydrate degradation products can retard the bioconversion of lignocellulose. In this work, liquid hot water (150 to 190 degrees C) and 1% H2SO4 pretreatments (130 to 190 degrees C) were used on sugarcane bagasse holocellulose for 3 h to generate pseudo-lignin. The effects of pseudo-lignin generation on structural characteristics and bioconversion of substrates were evaluated. The results showed that the formation of pseudo-lignin increased the hydrophobicity of the substrates. After LHW pretreatments and acid pretreatments at low temperatures (<150 C), most of the xylans were removed, yielding 2.1 to 5.4% pseudo-lignin. Increasing acid pretreatment temperature to 170 and 190 degrees C yielded 34.3% and 93.6% pseudo-lignin, respectively. After pretreatment, the accessibilities and bioconversions of substrates were enhanced by degradation of xylans, increasing glucose conversions and bioethanol productions of substrates from 53.2 to 85.3%, and 9.9 to 13.1 g/L, respectively. However, large amounts of pseudo-lignin were generated during acid pretreatments at 170 degrees C, reducing glucose conversion and bioethanol yield to 45.6% and 6.3 g/L, respectively.

Automated summary

Pseudo-lignin derived from the condensation of carbohydrate degradation products can affect the hydrophobicity of substrates and their accessibility for bioconversion. Degradation of xylans during pretreatment enhances the bioconversion of substrates, while high-temperature acid pretreatment results in excessive pseudo-lignin generation and decreased ethanol yields.