The Effect Of Lignosulfonate On The Rheology And Enzymatic Hydrolysis Of High-solid Corncob Slurries

The conversion of lignocellulosic biomass to biofuels and other chemicals through lignocellulose-to-sugar platform has been recognized as an effective way to ease energy crisis and reduce environmental pollution. Current conversion process of ethanol fuel utilizing lignocelluloses as a substrate involves pretreatment, enzymatic hydrolysis, fermentation and distillation. Corncob, as a low-cost abundant agricultural residue, has been regarded as an important feedstock for furfural and xylose production due to its high xylan content. Because the process of production has greatly removed its hemicellulose fraction and destroyed its lignocellulose cell wall structure and its cellulose content is high, corncob residues are cheap raw material for ethanol without pretreatment. To make the subsequent distillation economical, enzymatic hydrolysis should be conducted at high-solid loading to increase the concentration of sugar and ethanol and decrease the cost of distillation. However, the solid-loading is an essential parameter to affect the enzymatic hydrolysis e?ciency and the rheological properties of lignocellulose. Therefore, the improvement of enzymatic hydrolysis e?ciency and rheological properties of lignocellulosic substrate at high-solid loading is important for the industrial production of cellulosic ethanol.The effects of lignosulfonate(SXSL) on the rheology and enzymatic hydrolysis of high-solid corncob slurries were investigated. The application of 2.5%(w/w) SXSL increased the substrate enzymatic digestibility(SED) of high-solid corncob slurries at 72 h from 31.7% to 54.0%. The results also showed that SXSL have strong enhancement on enzymatic hydrolysis of corncob residues in the different buffer p H, however it resulted in the increase of the slurry’s yield stress from 77.5 Pa to 140 Pa and the complex viscosity increased from 35968 Pa·s to 39060 Pa·s. Although SXSL improved the enzymatic hydrolysis of high-solid corncob slurry, it increased the slurry’s yield stress and complex viscosity.Hexadecyl trimethyl ammonium bromide(CTAB) and long-chain fatty alcohols(LFAs) were applied to increase the SED and improve the rheological properties of high-solid corncob slurries with the addition of SXSL. The study found that the compound of SXSL and CTAB has a stronger enhancing effect on the enzymatic hydrolysis of high-solid corncob slurry, but the compound of SXSL and CTAB has no significant improvement in the rheology of high-solid slurry. In the presence of 2.5% SXSL, 2.5% n-Octanol(C8) and n-Decanol(C10) increased the SED at 72 h from 54.0% to 60.3% and 58.7%, respectively. Meanwhile, the yield stress of high-solid corncob slurry decreased to 86.7 Pa and 58.7 Pa, and the complex viscosity decreased to 21850 Pa·s and 14770 Pa·s. The results indicated that LFAs clearly enhanced the enzymatic hydrolysis of high-solid corncob slurries with SXSL. Furthermore, LFAs could improve the rheology of high-solid corncob slurry with the application of SXSL, and the improvement of LFAs increases with the carbon chain length.Four SXSL fractions prepared by ultra?ltration were applied to compare the enzymatic hydrolysis e?ciency and rheological properties of high-solid corncob slurry at the same loading of 2.5% with and without LFAs. In the absence of LFAs, all SXSL fractions enhanced the enzymatic hydrolysis of high-solid corncob and the order of enhancement at 72 h is SL4 > SL3 ≈ SL2 > SL1. The smallest molecular weight(MW) SXSL fraction had the strongest enhancement on SED. However, all SXSL fractions had no significant improvement in the rheology of high-solid slurry and the SXSL fraction with large MW had a negative effect on rheology. LFAs improved the rheological properties of high-solid slurry and were strong enough to counteract the negative effect of SXSL fractions.