Enhanced Enzymatic Hydrolysis of Poplar after Combined Dilute NaOH and Fenton Pretreatment

Abstract

Five types of pretreatment processes were investigated to confirm the enhancement of the enzymatic hydrolysis of poplar. These processes included a hot water pretreatment, a calcium oxide pretreatment, NaOH extraction at low temperature, a Fenton reaction, and a combined dilute NaOH and Fenton pretreatment. The combined dilute NaOH and Fenton pretreatment was found to be the most effective pretreatment process. After enzymatic hydrolysis for 72 h, 74% of the cellulose recovery yield was obtained when the poplar substrates were pretreated with 2% NaOH at 75 °C for 3 h, followed by 20 mmol/g of H2O2 (30%) and 0.2 mmol/g of FeSO4·7H2O for a Fenton reaction period of 12 h. The cellulose recovery yield was approximately five-fold greater than that of the untreated sample directly processed by enzymatic hydrolysis. Furthermore, microscopic observations of changes in the surface structure of the pretreated residue were correlated with the enhancement of the enzymatic hydrolysis of cellulose. In conclusion, the combined dilute NaOH and Fenton pretreatment shows high potential for future application.

A Comparison of NaOH, Fenton, and Their Combined Pretreatments for Improving Saccharification of Corn Stalks

“…From the literature, the basic parameters involved in combinative pretreatment were considered to include particle size, and NaOH and Fenton loading. ,,,, A two-level Plackett–Burman experimental design (PBD) of 12 runs was introduced to screen the important variables significantly influencing the pretreatment efficiency. The Fenton loading was studied between 0.57 and 1.13 mmol/g-TS (on a Fe 2+ concentration basis) to investigate the effect of Fenton oxidation treatment.…”

“…In recent years, other methods, such as Fenton oxidation (FO) which mimics the degradation of plant cell walls by fungi, were used to pretreat lignocellulosic biomass . The mechanism of action of FO is the generation of two kinds of hydroxyl radicals (HO· and HOO·) when Fe 2+ catalyzes H 2 O 2 decomposition under acidic conditions . The generated hydroxyl radicals could both depolymerize carbohydrates and lignin to breakdown lignocellulosic biomass, making it more accessible for enzymes .…”

“…The generated hydroxyl radicals could both depolymerize carbohydrates and lignin to breakdown lignocellulosic biomass, making it more accessible for enzymes . Since FO and NaOH extraction (AE) operate under different mechanisms of action, several works investigated the possibility that the combination of FO with NaOH extraction (AE) could be synergetic for herbaceous crops pretreatment. ,, Those previous studies optimized the process parameters of synergistic pretreatment by a one-factor-at-a time approach, which was performed by changing one independent variable while fixing all others at a fixed level. ,, So far, no statistical analysis has been performed to compare the effectiveness of these pretreatments for enzymatic saccharification of CS. On the other hand, the one-factor-at-a time method was difficult to pick out significantly affected factors due to the interactions among factors .…”

“…13 The mechanism of action of FO is the generation of two kinds of hydroxyl radicals (HO• and HOO•) when Fe 2+ catalyzes H 2 O 2 decomposition under acidic conditions. 14 The generated hydroxyl radicals could both depolymerize carbohydrates and lignin to breakdown lignocellulosic biomass, making it more accessible for enzymes. 15 Since FO and NaOH extraction (AE) operate under different mechanisms of action, several works investigated the possibility that the combination of FO with NaOH extraction (AE) could be synergetic for herbaceous crops pretreatment.…”

“…15 Since FO and NaOH extraction (AE) operate under different mechanisms of action, several works investigated the possibility that the combination of FO with NaOH extraction (AE) could be synergetic for herbaceous crops pretreatment. 14,16,17 Those previous studies optimized the process parameters of synergistic pretreatment by a one-factor-at-a time approach, which was performed by changing one independent variable while fixing all others at a fixed level. 14,16,17 So far, no statistical analysis has been performed to compare the effectiveness of these pretreatments for enzymatic saccharification of CS.…”