Production of xylooligosaccharides and monosaccharides from poplar by a two-step acetic acid and peroxide/acetic acid pretreatment

Abstract

Background Populus (poplar) tree species including hybrid varieties are considered as promising biomass feedstock for biofuels and biochemicals production due to their fast growing, short vegetative cycle, and widely distribution. In this work, poplar was pretreated with acetic acid (AC) to produce xylooligosaccharides (XOS), and hydrogen peroxide–acetic acid (HPAC) was used to remove residual lignin in AC-pretreated poplar for enzymatic hydrolysis. The aim of this work is to produce XOS and monosaccharides from poplar by a two-step pretreatment method. Results The optimal conditions for the AC pretreatment were 170 °C, 5% AC, and 30 min, giving a XOS yield of 55.8%. The optimal HPAC pretreatment conditions were 60 °C, 2 h, and 80% HPAC, resulting in 92.7% delignification and 87.8% cellulose retention in the AC-pretreated poplar. The two step-treated poplar presented 86.6% glucose yield and 89.0% xylose yield by enzymatic hydrolysis with a cellulases loading of 7.2 m/g dry mass. Very high glucose (93.8%) and xylose (94.6%) yields were obtained with 14.3 mg cellulases/g dry mass. Both Tween 80 and β-glucosidase enhanced glucose yield of HPAC-pretreated poplar by alleviating the accumulation of cellobiose. Under the optimal conditions, 6.9 g XOS, 40.3 g glucose, and 8.9 g xylose were produced from 100 g poplar. Conclusions The AC and HPAC pretreatment of poplar represented an efficient strategy to produce XOS and fermentable sugars with high yields. This two-step pretreatment was a recyclable benign and advantageous scheme for biorefinery of the poplar into XOS and monosaccharides. Electronic supplementary material The online version of this article (10.1186/s13068-019-1423-x) contains supplementary material, which is available to authorized users.

Oxygen radical based on non-thermal atmospheric pressure plasma alleviates lignin-derived phenolic toxicity in yeast

“…Various biological, chemical, and physical pretreatment methods have been developed [8][9][10][11][12]. For economic reasons, alkaline hydrolysis is commonly used to prepare lignocelluloses for enzymatic saccharification and fermentation [58]; however, vanillin is generated as a toxic byproduct during this process [13,14].…”

“…Bioethanol production from lignocellulose generally involves three steps: (1) pretreatment to break down complex lignocellulose structures, (2) enzymatic hydrolysis of polysaccharides (i.e., cellulose and hemicellulose) into fermentable sugars, and (3) fermentation to convert sugars into ethanol [5]. Pretreatment is required to alter the biomass by changing its chemical or physical properties and to allow increased enzyme accessibility to cellulose [6,7], with various biological, chemical, and physical pretreatment methods having been developed [8][9][10][11][12]. Vanillin is generally generated as a byproduct during the process of fermentable-sugar production from lignocellulosic biomass, regardless of being herbage, softwood, or hardwood [13,14].…”

Co-production of Xylooligosaccharides and Xylose From Poplar Sawdust by Recombinant Endo-1,4-β-Xylanase and β-Xylosidase Mixture Hydrolysis

“…In the biomass industry, XOS and xylose can be converted into ethanol, furfural, and other valuable fuels or chemicals (Zhang et al, 2015 ; Li et al, 2020a ; Wang and Fang, 2020 ). At present, various pretreatment methods, such as self-hydrolysis, enzymatic hydrolysis, acid hydrolysis, microwave-assisted method, and enzymatic acid hydrolysis can be used to degrade xylan to obtain XOS with different polymerization degrees (Wei et al, 2018 ; Li et al, 2019b ; Wen et al, 2019 ; Jun et al, 2020 ). Among these methods, through the self-hydrolysis of lignocellulose, the yield is low, and the by-products are multiple; the acid hydrolysis method using sulfuric acid or hydrochloric acid brings great burden to the environment.…”

Alkaline post-incubation improves the saccharification of poplar after hydrogen peroxide–acetic acid pretreatment

“…100% HPAA pretreatment can remove 90.3% lignin of Jerusalem artichoke and improve enzymatic hydrolysis yield to 86.0% [ 9 ]. However, after the acetic acid-pretreated poplar was pretreated with 100% HPAA at 60 °C, the acetyl group increased from 5.9% to 8.0% [ 11 ]. The acetyl groups in glucan and xylan impacts its hydrolysis by cellulase or xylanase due to the steric hindrance of the acetyl groups [ 12 – 14 ].…”

“…The acetyl groups in glucan and xylan impacts its hydrolysis by cellulase or xylanase due to the steric hindrance of the acetyl groups [ 12 – 14 ]. Pretreatment with 0.1% sodium hydroxide can increase the glucose yield of HPAA-pretreated poplar from 67.2% to 74.4% [ 11 ]. However, the effect of sodium hydroxide incubation on the removal of acetyl in poplar has not been investigated.…”