Structural features of dilute acid, steam exploded, and alkali pretreated mustard stalk and their impact on enzymatic hydrolysis

Abstract

To overcome the recalcitrant nature of biomass several pretreatment methodologies have been explored to make it amenable to enzymatic hydrolysis. These methodologies alter cell wall structure primarily by removing/altering hemicelluloses and lignin. In this work, alkali, dilute acid, steam explosion pretreatment are systematically studied for mustard stalk. To assess the structural variability after pretreatment, chemical analysis, surface area, crystallinity index, accessibility of cellulose, FT-IR and thermal analysis are conducted. Although the extent of enzymatic hydrolysis varies upon the methodologies used, nevertheless, cellulose conversion increases from <10% to 81% after pretreatment. Glucose yield at 2 and 72h are well correlated with surface area and maximum adsorption capacity. However, no such relationship is observed for xylose yield. Mass balance of the process is also studied. Dilute acid pretreatment is the best methodology in terms of maximum sugar yield at lower enzyme loading.

Keywords: Acetic acid (PubChem CID: 176); Cellulose (PubChem CID: 14055602); Chemical pretreatment; Fermentable sugars; Formic acid (PubChem CID: 284); Furfural (PubChem CID: 7362); Glucose (PubChem CID: 79025); Hydrolysis; Hydroxymethyl furfural (PubChem CID: 237332); Lignin (PubChem CID: 73555271); Mustard stalk; Sodium Hydroxide (PubChem CID: 14798); Steam explosion; Sulphuric acid (PubChem CID:1118); Xylose (PubChem CID: 644160).