Improvement Of Enzymatic Hydrolysis Research Articles

Distinct effects of dilute acid prehydrolysate inhibitors on enzymatic hydrolysis and yeast fermentation.

The effects of dilute acid prehydrolysate from poplar were investigated and compared in the enzymatic hydrolysis, fermentation, and simultaneous saccharification fermentation (SSF) in this study. The improvement of enzymatic hydrolysis and fermentation with resin adsorption and surfactant addition has also been represented. A total of 16 phenolic alcohols, aldehydes, acids and 3 furan derivatives in the prehydrolysates were identified and quantified by gas chromatography/mass spectrometry (GC/MS). The degree of inhibition from the phenolic compounds (26.55%) in prehydrolysate on the enzymatic hydrolysis was much higher than carbohydrates-derived inhibitors (0.52-4.64%). Around 40% degree of inhibition was eliminated in Avicel enzymatic hydrolysis when 75% of prehydrolysates phenolic compounds were removed by resin adsorption. This showed distinguishing inhibition degrees of various prehydrolysate phenolic compounds. Inhibition of prehydrolysate on enzymatic hydrolysis was more dosage-dependent, while their suppression on the fermentation showed a more complicated mode: fermentation could be terminated by the untreated prehydrolysate, while a small number of prehydrolysate inhibitors even improved the glucose consumption and ethanol production in the fermentation. Correlated with this distinct inhibition modes of prehydrolysate, the improvement of Tween 80 addition in SSF was around 7.10% for the final ethanol yield when the glucose accumulation was promoted by 76.6%.

Improved high solids loading enzymatic hydrolysis and fermentation of cotton microdust by surfactant addition and optimization of pretreatment

Cotton microdust (CMD) was pretreated by a two-stage alkali-acid pretreatment and subsequently subjected to high solids loading enzymatic hydrolysis (HSLEH) and fermentation. The efficiency of the HSLEH of pretreated CMD was enhanced by optimizing the pretreatment condition using central composite design (CCD) and further improvement of enzymatic hydrolysis was facilitated by the addition of surfactant polyethylene glycol (PEG). The predicted optimized pretreatment conditions for maximum digestibility of cellulose from the regression model were 0.8 % (w/v) H2SO4 and 163 °C. The pretreated CMD was efficiently hydrolyzed at high solids loading (35 %) to produce high glucose concentration. When PEG was added to the HSLEH mixture with a lower cellulase loading of 22 FPU/g glucan, the concentration of glucose produced was 134 g/L. The fermentation of glucose after the surfactant assisted HSLEH at 35 % solids loading produced 66 g/L of ethanol with 96 % metabolic yield. The observed levels of reduction of cellulase load and improvement of ethanol production are higher than the reported values for cotton gin wastes. Hence the observed results demonstrated the feasibility of producing high concentration of ethanol from CMD, which would be useful for further improvement and scale-up of the process.

Comparative study on enzymatic digestibility of acid-pretreated poplar and larch based on a comprehensive analysis of the lignin-derived recalcitrance

Enzymatic digestibility of an acid-pretreated poplar (AP, 42.9%) was superior to that of a similarly acid-pretreated larch (AL, 12.5%). Effects of lignin-related recalcitrance on enzymatic hydrolysis were comprehensively investigated by disrupting the two predominant lignin fractions present in acid-pretreated material (extractable lignin and bulk lignin). Lignin removal and bovine serum albumin (BSA) addition were performed to estimate the relative contributions of lignin towards physical blocking and enzyme binding on enzymatic hydrolysis. The lignin physical blocking played a more significant role in limiting the enzymatic hydrolysis of AL. BSA addition improved enzymatic hydrolysis of AP more significantly than AL. Moreover, the effects of lignin embedded in the lignocellulosic matrix on enzyme non-productive binding were compared with the isolated lignin. It indicated that the lignin distribution would influence the lignin effects on enzyme non-productive binding during enzymatic hydrolysis. Results will give insights towards improvement of enzymatic hydrolysis on acid-pretreated woody biomass.

Comparative study on different pretreatment on enzymatic hydrolysis of corncob residues

Under the situation of increasingly severe challenge of energy consumption, it is of great importance to make full use of bioresources such as forestry and agricultural residues. Herein, the corncob residues generated after processing corncob were enzymatically hydrolyzed to yield fermentable sugars. To overcome the recalcitrance of corncob residues, three kinds of pretreatment methods, i.e., sulfonation, PFI refining, and wet grinding, were applied; their effects on enzymatic hydrolysis and main characteristics of corncob residues substrate were investigated. The results showed that the enzymatic digestibility of the substrate was greatly enhanced by employing each method. The wet grinding exhibited obvious advantages, e.g., the conversion yield of cellulose to glucose and glucose concentration reached 96.7% and 32.2 g/L after 59 h of enzymatic hydrolysis, respectively. The improvement in enzymatic hydrolysis was mainly attributed to the altered characteristics of the substrate such as swelling ability, specific surface area, and particle size and distribution.

Improvement of enzymatic hydrolysis and ethanol production from corn stalk by alkali and N-methylmorpholine-N-oxide pretreatments

A combinative technology of alkali and N-methylmorpholine-N-oxide (NMMO) was used to pretreat corn stalk (CS) for improving the efficiencies of subsequent enzymatic hydrolysis and ethanol fermentation. The results showed that this strategy could not only remove hemicellulose and lignin but also decrease the crystallinity of cellulose. About 98.0% of enzymatic hydrolysis yield was obtained from the pretreated CS as compared with 46.9% from the untreated sample. The yield for corresponding ethanol yield was 64.6% while untreated CS was only 18.8%. Besides, xylose yield obtained from the untreated CS was only 11.1%, while this value was 93.8% for alkali with NMMO pretreated sample. These results suggest that a combination of alkali with 50% (wt/wt) NMMO solution may be a promising alternative for pretreatment of lignocellulose, which can increase the productions of subsequent enzymatic hydrolysis and ethanol fermentation.

Post-treatment mechanical refining as a method to improve overall sugar recovery of steam pretreated hybrid poplar

This study investigates the effect of mechanical refining to improve the sugar yield from biomass processed under a wide range of steam pretreatment conditions. Hybrid poplar chips were steam pretreated using six different conditions with or without SO2. The resulting water insoluble fractions were subjected to mechanical refining. After refining, poplar pretreated at 205°C for 10min without SO2 obtained a 32% improvement in enzymatic hydrolysis and achieved similar overall monomeric sugar recovery (539kg/tonne) to samples pretreated with SO2. Refining did not improve hydrolyzability of samples pretreated at more severe conditions, nor did it improve the overall sugar recovery. By maximizing overall sugar recovery, refining could partially decouple the pretreatment from other unit operations, and enable the use of low temperature, non-sulfur pretreatment conditions. The study demonstrates the possibility of using post-treatment refining to accommodate potential pretreatment process upsets without sacrificing sugar yields.

Improvement in Enzymatic Hydrolysis of Waste Office Paper with Chemical Pretreatment and Enzyme Loading Reduced

This work evaluates the effects of increasing hydrolysis time, enzyme loading and mass of substrate on the formation of glucose in the enzymatic hydrolysis of waste office paper, after chemical or physical pre-treatment. Initially, for this study, a factorial design 24 was applied. The type of pretreatment was the only significant effect on the glucose release. Maximum glucose concentration was less than 0.5 g/L, when physical pre-treatment was used. Physical pre-treatment was therefore discarded. A new factorial design with three factors and higher number of level of treatments (hydrolysis time—24, 48 and 72 h; enzyme loading—5.2, 7.8 and 10.4 FPU/g substrate; mass of waste office paper—2.25, 3.00 and 3.75 g) was applied, after chemical pre-treatment. The increase in mass of paper increased the glucose concentration. On the other hand, the increase time of hydrolysis or enzyme loading did not influence glucose release. Maximum glucose concentration (23 g/L) was about 50 times higher than that obtained when physical pretreatment was used, reducing by half the enzyme load. Optimum conditions of enzymatic hydrolysis was obtained at 24 h of hydrolysis, using lower enzyme loading (5.2 FPU/g) and higher mass of waste office paper (3.75 g; 7.5 % w/V), after chemical pre-treatment.

Chemical and structural analysis of alkali pretreated pinewood for efficient ethanol production

Improvement of enzymatic hydrolysis and ethanol production from softwood pine was conducted by pretreatment with 8% (w/v) NaOH at different temperatures of 0, 25, and 80 °C for 2 h.

Improvement of Enzymatic Hydrolysis of Whole Slurry from Bisulfite-Pretreated Furfural Residues with Low Enzyme Loading

Improvement of Enzymatic Hydrolysis of Whole Slurry from Bisulfite-Pretreated Furfural Residues with Low Enzyme Loading

Hydrophilic pretreatment of furfural residues to improve enzymatic hydrolysis

Furfural residues (FRs) is an industrial waste material with an enormous potential for bio-ethanol production. In this study, FRs were pretreated with green liquor (GL) combined with hydrogen peroxide (GL–H2O2) or ethanol (GL-ethanol). The wettability and electrostatic contributions of untreated and pretreated FRs was investigated as well as that of isolated lignin cellulolytic enzyme lignin (CEL) and cellulose. The results showed that the hydrophilicity of FRs was increased after GL–H2O2 and GL-ethanol pretreatment. Lignin is the key factor that affects the hydrophilicity of substrate. The cellulase binding for lignin was reduced due to the increase of hydrophilicity of lignin, resulting in the improvement of enzymatic hydrolysis. The electrostatic contributions was also an important factor that influenced the cellulase binding of lignin. After pretreatments, the negative charge of lignin was decreased. Accordingly, the cellulase binding capacity was reduced. This effect was more significant after the GL-ethanol pretreatment. Thus, the glucose yield of the substrate obtained from the GL-ethanol pretreatment (86.1 %) was larger than that from the GL–H2O2 pretreatment (82.2 %). Unlike the CEL, GL–H2O2 pretreatment increased the negative charge of cellulose. And the increase of negative charge improved the affinity of cellulose to cellulase via electrostatic attraction. The XPS analyses indicated that the carbonyl groups from lignin play an important role in decreasing the hydrophobicity of the substrates.

Catalysis with CuII(bpy) improves alkaline hydrogen peroxide pretreatment

Copper(II) 2,2'-bipyridine (Cu(II) (bpy))-catalyzed alkaline hydrogen peroxide (AHP) pretreatment was performed on three biomass feedstocks including alkali pre-extracted switchgrass, silver birch, and a hybrid poplar cultivar. This catalytic approach was found to improve the subsequent enzymatic hydrolysis of plant cell wall polysaccharides to monosaccharides for all biomass types at alkaline pH relative to uncatalyzed pretreatment. The hybrid poplar exhibited the most significant improvement in enzymatic hydrolysis with monomeric sugar release and conversions more than doubling from 30% to 61% glucan conversion, while lignin solubilization was increased from 36.6% to 50.2% and hemicellulose solubilization was increased from 14.9% to 32.7%. It was found that Cu(II) (bpy)-catalyzed AHP pretreatment of cellulose resulted in significantly more depolymerization than uncatalyzed AHP pretreatment (78.4% vs. 49.4% decrease in estimated degree of polymerization) and that carboxyl content the cellulose was significantly increased as well (fivefold increase vs. twofold increase). Together, these results indicate that Cu(II) (bpy)-catalyzed AHP pretreatment represents a promising route to biomass deconstruction for bioenergy applications.

Ethanol Production from Cashew Apple Bagasse: Improvement of Enzymatic Hydrolysis by Microwave-Assisted Alkali Pretreatment

In this work, the potential of microwave-assisted alkali pretreatment in order to improve the rupture of the recalcitrant structures of the cashew able bagasse (CAB), lignocellulosic by-product in Brazil with no commercial value, is obtained from cashew apple process to juice production, was studied. First, biomass composition of CAB was determined, and the percentage of glucan and lignin was 20.54 ± 0.70% and 33.80 ± 1.30%, respectively. CAB content in terms of cellulose, hemicelluloses, and lignin, 19.21 ± 0.35%, 12.05 ± 0.37%, and 38.11 ± 0.08%, respectively, was also determined. Results showed that, after enzymatic hydrolysis, alkali concentration exerted influence on glucose formation, after pretreatment with 0.2 and 1.0 mo L(-1) of NaOH (372 ± 12 and 355 ± 37 mg g(glucan)(-1) ) when 2% (w/v) of cashew apple bagasse pretreated by microwave-assisted alkali pretreatment (CAB-M) was used. On the other hand, pretreatment time (15-30 min) and microwave power (600-900 W) exerted no significant effect on hydrolysis. On enzymatic hydrolysis step, improvement on solid percentage (16% w/v) and enzyme load (30 FPU g (CAB-M) (-1) ) increased glucose concentration to 15 g L(-1). The fermentation of the hydrolyzate by Saccharomyces cerevesiae resulted in ethanol concentration and productivity of 5.6 g L(-1) and 1.41 g L(-1) h(-1), respectively.

Improving Enzymatic Saccharification of Hybrid Poplar by Electron Beam Irradiation Pretreatment

The effects of electron beam irradiation pretreatment on the structural and compositional features and on the enzymatic saccharification of hybrid poplar were investigated. The carbohydrate compositional analyses with 1H-NMR spectroscopic method were applied in this study to investigate the change in the polysaccharides of hybrid poplar quantitatively. As the irradiation dose increased, the amount of extract produced in mild alkaline extraction was increased. The composition of the residual biomass after mild alkaline extraction was also changed depending on the electron beam irradiation dose. Especially for xylose, the peak intensity in NMR spectra was decreased with increasing electron irradiation dose, which demonstrated the significant decomposition of xylan caused by the electron beam irradiation. The changes induced by electron beam irradiation resulted in a better response to enzymatic hydrolysis with commercial cellulases (Celluclast 1.5 L and Novozym 342). More improvement in enzymatic hydrolysis by the irradiation was found in the hydrolysis of the xylan than that of the cellulose in hybrid poplar.

Improving enzymatic hydrolysis of industrial hemp ( Cannabis sativa L.) by electron beam irradiation

The electron beam irradiation was applied as a pretreatment of the enzymatic hydrolysis of hemp biomass with doses of 150, 300 and 450 kGy. The higher irradiation dose resulted in the more extraction with hot-water extraction or 1% sodium hydroxide solution extraction. The higher solubility of the treated sample was originated from the chains scission during irradiation, which was indirectly demonstrated by the increase of carbonyl groups as shown in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra. The changes in the micro-structure of hemp resulted in the better response to enzymatic hydrolysis with commercial cellulases (Celluclast 1.5L and Novozym 342). The improvement in enzymatic hydrolysis by the irradiation was more evident in the hydrolysis of the xylan than in that of the cellulose.