A Combination Method of Liquid Hot Water and Phosphotungstic Acid Pretreatment for Improving the Enzymatic Saccharification Efficiency of Rice Straw

Abstract

Chemical pretreatment can significantly improve the enzymatic hydrolysis efficiency of lignocellulosic biomass, thereby improving the yield of sugar materials for the production of cellulosic ethanol, but commonly used acid–base catalysts are difficult to recover and reuse. In this work, a combination method of liquid hot water (LHW) and phosphotungstic acid (PTA) pretreatment was performed to improve the saccharification efficiency of rice straw, and we attempted to evaluate the reuse effect of PTA catalysts. The rice straw was first treated with LHW at 180 °C for 90 min, and then treated with 20 mM PTA at 130 °C for 60 min. After pretreatment, the cellulose hydrolysis efficiency and glucose recovery of the rice straw increased by 201.85% and 164.25%, respectively. Glucose accounted for 96.8% of the total reducing sugar in the final enzymatic hydrolysate. After each PTA pretreatment, approximately 70.8–73.2% of the PTA catalyst could be recycled. Moreover, the catalytic activity of the PTA catalyst that had been used five times did not decrease. The improved enzymatic saccharification efficiency was attributed to the removal of 89.24% hemicellulose and 21.33% lignin from the lignocellulosic substrate. The two-step LHW-PTA pretreatment could pretreat biomass in the field of cellulosic ethanol production.

Biological conversion of agricultural wastes into indole-3-acetic acid by S. lavenduligriseus BS50-1 using response surface methodology (RSM)

“…The crystallinity index of pretreated bagasse was observed due to the elimination of the amorphous structure of hemicellulose and lignin; nevertheless, the crystalline structure of cellulose was relatively unaffected. Previously, increases in lignocellulose crystallinity were observed in various lignocelluloses pretreated with LHW, for instance, rice straw pretreated with LHW 25 and other pretreatment methods, e.g., dilute acid pretreatment 26 and alkaline pretreatment 27 . On the other hand, certain pretreatment techniques, such as ionic liquids, have been reported to cause complete destruction of the crystalline cellulose structure 28 .…”

Biological Conversion of Agricultural Wastes into Indole-3-acetic Acid by Streptomyces lavenduligriseus BS50-1 Using a Response Surface Methodology (RSM)

“…The increased crystallinity index of the pretreated bagasse was caused by the elimination of the amorphous hemicellulose and lignin structures; nevertheless, the crystalline structure of cellulose was relatively unaffected. Previous studies have found increased crystallinity indexes in various lignocelluloses pretreated with LHW, for example, rice straw pretreated with LHW, as well as other pretreatment methods such as dilute acid and alkaline pretreatment . However, certain pretreatment techniques such as those involving ionic liquids are known to completely destroy the crystalline cellulose structure .…”

A Value-Added Utilization Method of Sugar Production By-Products from Rice Straw: Extraction of Lignin and Evaluation of Its Antioxidant Activity

“…The process of producing glucose from rice straw was referred to the method of our previous study with some modifications [34]. Briefly, approximately 15 g of RS powder was extracted with absolute ethanol by the Soxhlet extraction method for 24 h and vacuum dried to obtain the extract-free RS.…”

“…In the previous study, a combined process of liquid hot water (LHW) and phosphotungstic acid (PTA) pretreatment and enzymatic hydrolysis was used to produce fermentable sugars from rice straw [34]. The glucose yield was about 27.6% by the mass of air-dried straw.…”