초록
<P><B>Abstract</B></P> <P>Comprehensive evaluation of an integrated process for cellulosic ethanol production from lactic acid+choline chloride+water (LA-CC-H<SUB>2</SUB>O) mixture based natural deep eutectic solvent (NADES) pretreated rice straw; solvent recovery and its reusability; extraction of value added products viz., lignin and xylan; enzymatic saccharification and fermentation were studied. Four separate processes viz. pretreatment at 5% (<I>w/v</I>) and 10% (<I>w/v</I>) solids loading and enzymatic hydrolysis at 10% (<I>w/v</I>) and 25% (<I>w/v</I>) solids loading were investigated. No significant difference was observed in holocellulose recovery and lignin solubility in all the tested processes. Hydrolysis at 10% (<I>w/v</I>) and 25% (<I>w/v</I>) solids loading produced maximum glucose yields of 38.6±1.2g/L and 90.3±2.3g/L, respectively. Additional concentration step of sugars is needed from 10% (<I>w/v</I>) hydrolysis for direct ethanol fermentation using <I>Clavispora</I> NRRL Y-50464, while this could be voided with 25% (<I>w/v</I>) hydrolysis sugars. Maximum ethanol yield of 36.7g/L was obtained with 9% (<I>w/v</I>) glucose with a theoretical conversion efficiency of 79.9% which estimated to produce ~129L of ethanol per ton of raw biomass. Alongside, NADES pretreatment resulted in solubilization of 72-75% (<I>w/v</I>) of biomass bound lignin from which 86–90% (<I>w/v</I>) of lignin was recovered. Additionally, >98% (<I>v/v</I>) of the treated NADES reagent was recovered and reused in three consecutive biomass pretreatment cycles with no loss in pretreatment efficiency. This study clearly demonstrated that pretreatment at 10% (<I>w/v</I>) solids loading followed by enzymatic hydrolysis at 25% (<I>w/v</I>) solids loading is the most effective integrated biorefinery process using NADES pretreated rice straw.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Four different process conditions for integrated biorefinery were evaluated. </LI> <LI> NADES reagent was used in biomass pretreatment of rice straw. </LI> <LI> Maximum recovery of solvents and water and its res-use. </LI> <LI> Biomass valorization by generating high purity by-products. </LI> <LI> High yield ethanol production from NADES pretreated rice straw. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>