Controlled instant pressure drop (DIC) pretreatment to enhance fractionation and enzymatic saccharification of poppy capsule waste

Abstract

Lignocellulosic biomass is an important resource for biofuels, chemicals, and bioproducts; however, deconstructing its recalcitrant structure is a challenge. In this study, controlled instant pressure drop (DIC)-assisted alkaline pretreatment process of poppy capsule waste (PCW) was developed and statistically optimized with the aim of enhanced fractionation efficiency and production of fermentable sugars and xylooligosaccharides (XOs). The effects of DIC process variables on PCW fractionation were investigated. The optimal DIC conditions were found as 5 bar vapor pressure, 540 s processing time, and 9% (w/w) moisture content. At the second stage, optimum conditions for alkaline extraction were found as 22.58% (w/w) KOH, 1-h extraction time, and 22.15 mL precipitant volume. Process optimization concluded a hemicellulose separation yield of 26.37±0.08%, corresponding to 104.7% increase. Process optimization also contributed to the sustainability of the process by reducing KOH and precipitant consumption by 9.7% and 11.4%, respectively, with a concurrent shortening of the processing time from 24 to 1 h. DIC pretreatment enhanced the enzymatic hydrolysis yield of PCW, and a maximum glucan-to-glucose conversion yield of 22.85±0.74% was obtained, which corresponds to a 9-fold increase. Hydrolysis of PCW and hemicellulose-rich fraction by xylanase yielded xylose-free xylobiose (X2) as the principal product. SEM analysis demonstrated the expansion of PCW structure by DIC pretreatment, reasoning the higher fractionation efficiency and enzymatic hydrolysis yields. The optimized process could be an efficient option for lignocellulose fractionation, enzymatic saccharification, and XOs production within biorefinery concept while reducing the requirement for chemicals and processing time.