Effect of chemical pretreatments on the fermentation and ultimate digestibility of bagasse by <i>Phanerochaete chrysosporium</i>

Abstract

Abstract When sugarcane bagasse was pretreated at room temperature with various chemicals singly or in combination, (0.25 m NaOH; 0.5 m H 2 SO 4 ; 2.6 M NH 3 ;0.14 M Ca(OH) 2 +0.12 M Na 2 CO 3 ;4.2 m EDA; and 0.5 M H 2 SO 4 or 0.25 M NaOH followed by 4.2 M EDA), increases in in‐vitro digestibility range from 28.9 to 48.6% depending on the particular chemicals. With most pretreatments, the hemicellulose content decreased and the cellulose content increased slightly, while lignin levels decreased only with NaOH + EDA pretreatments. Further fermentation of the chemically pretreated bagasse with Phanerochaete chrysosporium gave increased digestibilities, the highest final digestibility (59%) being achieved by pre‐treatment with 0.25 M NaOH. Pretreatment with NaOH or Ca(OH) 2 +Na 2 CO 3 and fermentation gave greatly increased levels of hemi‐cellulose and cellulose and substantial decreases in lignin levels. Chemical pretreatments of bagasse together with autoclaving considerably enhanced in‐vitro digestibility (up to 75%) and lignin degradation (1.4%). Pretreatment with NaOH, Ca(OH) 2 +Na 2 CO 3 , and EDA plus autoclaving gave large increases in total hemicelluloses and cellulose and marked decreases in lignin. Further fermentation with P. chrysosporium gave only slight increases in digestibility.