Pretreatment Enzymatic Hydrolysis Research Articles

A comparison on phosphorus release and struvite recovery from waste activated sludge by different treatment methods

Enhancing phosphorus (P) recovery from P-rich waste activated sludge is economically effective for sustainable development and long-term food security. It is the first step for struvite recovery to find a new way to release phosphorus fully from the waste activated sludge. In this study, food-processing wastewater was found to contribute to phosphorus-rich activated sludge, which was suitable for the recovery of phosphorus in comparison with sewage sludge. In addition, six sludge treatment methods were examined resulting in significant differences on the release and recovery performance of phosphorus and nitrogen. Enzymatic hydrolysis (EH) pre-treatment showed better phosphorus release while thermal hydrolysis (TH) pre-treatment was beneficial for nitrogen release. Anaerobic fermentation (AF) after sludge pre-treatment significantly increased the accumulation of ammonia nitrogen (around 34% of sludge total nitrogen, TN) and orthophosphate (around 68% of sludge total phosphorus, TP) in the hydrolysate for struvite recovery. The highest P recovery rate was obtained using a combined EH-AF (67.98% of sludge TP). Although non-pretreated AF and free nitrous acid hydrolysis (FNAH)-AF could also achieve comparable release of phosphorus and nitrogen, the purity of struvite obtained by EH, TH, EH-AF and TH-AF was better than the former. This study provides important information on the effects of different sludge treatment methods to the release of nitrogen and phosphorus to guide the application.

Effect of Mechanical Pretreatment for Enzymatic Hydrolysis of Woody Residues, Corn Stover and Alfalfa

This work aimed to investigate the effects of biomass species on fermentable sugar production, with respect to both energy consumption and sugar yield, using the modified traditional mechanical system from Pulp & Paper Mills as a potential biorefinery step. The study explored four lignocellulosic biomass species including corn stover, alfalfa, white birch and black spruce during the pretreatment process with and without the addition of NaOH. This was followed by a disk refining pretreatment under various operating conditions of gap size and consistency through a pilot scaled disk refining system. The study characterized and analyzed the chemical components and sugar streams obtained from the biomasses using the thermochemical and refining pretreatment and also analyzed the energy consumption of the disk refining system. The results show that for all the biomasses, the thermochemical process mainly removed lignin and hemicelluloses through a steaming pretreatment. From low to high, the lignin contents of the four biomasses are shown as follows: corn stover, alfalfa, white birch and black spruce. With respect to the refining pretreatment, when the gap size remains constant, black spruce has the longest fibers while corn stover has the shortest. Moreover, using enzymatic hydrolysis to evaluate the sugar yield revealed that the thermochemical pretreatment increased the sugar yield in accordance with how much lignin was removed from each biomass as well as their final lignin content. However, the additional refining treatment had a greater effect on corn stover and alfalfa than on white birch and black spruce due to the reduction in fiber length. Therefore, with respect to existing mechanical refining equipment, the modified thermochemical disk refining pretreatment (TCDRP) has a greater effect on agricultural biomass and hardwood (white birch). Specifically, the sugar yield of the TCDRP corn stover was the highest (97.3%) when compared to the other biomasses, while its energy consumption was 196 kWh/ton.

Chemical-free pretreatment of unwashed oil palm empty fruit bunch by using locally isolated fungus (Schizophyllum commune ENN1) for delignification

Biological pretreatment of unwashed oil palm empty fruit bunch (OPEFB) by Schizopyllum commune ENN1 was carried out to obtain optimum conditions of delignification. Locally isolated fungus, S. commune ENN1, was grown on oily OPEFB and the biomass was simultaneously delignified. Hence, the incubation time (7d–28d), temperature (25°C–40°C), and amount of substrate (3g–9g) were investigated to improve the efficiency of lignin removal during the biological pretreatment. Maximum lignin peroxidase and manganese peroxidase were produced at each optimal parameter, and correlated with maximum lignin removal. A similar pattern of maximum cellulase was produced by S. commune ENN1 at optimal parameters with only minimal activity of around 5U/g (CMCase). A maximum lignin removal of 67.9% was achieved at optimum condition at a temperature of 30°C by using 5g of OPEFB after 14d of incubation time. The cellulose content was increased by 31.7% of the biologically pretreated OPEFB at optimum condition. These findings showed that S. commune ENN1 was feasible to remove the lignin and increase the cellulose content of unwashed OPEFB through biological pretreatment for enzymatic hydrolysis.

Effect of multi-frequency counter-current S type ultrasound pretreatment on the enzymatic hydrolysis of defatted corn germ protein: Kinetics and thermodynamics

Abstract In this paper, the impact of ultrasound pretreatment on the kinetics and thermodynamics of defatted corn germ protein (DCGP) enzymatic hydrolysis was evaluated. The enzymatic hydrolysis kinetics and thermodynamics were studied for traditional method and ultrasonic pretreatments with a single-frequency counter-current S type (20 KHz) (SFU) and a multi-frequency counter-current S type (20, 28, 35 and 40 KHz) (MFU). The results showed that the traditional, SFU and MFU pretreated enzymatic hydrolysis of DCGP followed the First-order kinetic model. Again, the SFU and MFU pretreatments enhanced the enzymatic hydrolysis of DCGP. Compared to traditional enzymatic hydrolysis, the reaction rate constant values were increased by 50.0%, 54.7%, 47.8% and 52.3% for SFU pretreated enzymatic hydrolysis, and 58.0%, 58.5, 53.6% and 54.7% for MFU pretreated enzymatic hydrolysis at 20, 30, 40 and 50 oC respectively. Also, the results showed that the SFU and MFU ultrasound pretreatments of DCGP reduced the thermodynamic parameters which included the activation energy (Ea), enthalpy (ΔH), entropies (ΔS) and Gibbs free energy (ΔG) in enzymatic hydrolysis reaction.

Heteropoly acids enhanced neutral deep eutectic solvent pretreatment for enzymatic hydrolysis and ethanol fermentation of Miscanthus x giganteus under mild conditions

To improve the neutral DES (choline chloride/glycerol) pretreatment performance, three environmentally friendly heteropoly acids (phosphotungstic, phosphomolybdic and silicotungstic acids) were used as catalysts. Pretreatment with silicotungstic acid at 120 °C for 3 h resulted in 97.3% of enzymatic digestibility at an enzyme loading of 15FPU/g substrate, which was approximately eight times more than that of raw samples. More importantly, 80% of glucose yield was obtained within 12 h. Simultaneously, 81.8% of ethanol yield was achieved in the SSSF process. The efficient conversion was ascribed to the significant delignification (89.5%), which resulted in the exposure of more accessible specific surface area. This was attributed to that the proton (H+) from heteropoly acids could significantly contribute to the lignin degradation. Intriguingly, trace acetic acid (0.39 g/L) and HMF (0.21–0.95 g/L) in the pretreatment liquor were produced without any significant deleterious effects. These discoveries provide new insights for efficient biomass conversion under mild conditions.

Improvement of bioethanol production from pomegranate peels via acidic pretreatment and enzymatic hydrolysis.

The aim of this study was to improve the ethanol production from pomegranate peels (PPs). Therefore, the effect of enzymatic hydrolysis and different pretreatments on ethanol production by yeasts was examined. There were three different enzyme concentrations (3.6, 7.2, 14.4 FPU/g substrate) tested for enzymatic hydrolysis, and four different PP media, such as WSPP (whole slurry of PP), LFPP (liquid fraction of PP), WSFPP (washed solid fraction of PP) and N-WSFPP (non-washed solid fraction of PP), were prepared. Bioethanol production was monitored for 96 h. Maximum ethanol concentrations were obtained at WSPP medium as 12.69 g/L, 14.35 g/L and 4.23 g/L in Saccharomyces cerevisiae, Kluyveromyces marxianus and Pichia stipitis, respectively. On the other hand, the washing step of biomass increased the kinetic parameters dramatically and the highest theoretical ethanol yields and YP/S values were obtained from WSFPP medium in all tested yeasts. Theoretical ethanol yields were 97.8%, 98.7% and 35.5% for S. cerevisiae, K. marxianus and P. stipitis, respectively. Qp values were observed as 0.98 g/L h, 0.99 g/L h and 0.04 g/L h for the same yeasts. The highest YP/S values were detected as 0.50 g/g for S. cerevisiae, 0.50 g/g for K. marxianus and 0.30 g/g for P. stipitis in the washed pomegranate peel biomass.

Development of novel processes for the aqueous extraction of natural rubber from Taraxacum kok‐saghyz (TK)

AbstractBACKGROUNDTaraxacum kok‐saghyz (TK) is a rubber‐producing plant being developed as a commercial alternative source of natural rubber (NR). The objective of this study was to investigate processes to extract high quality NR at high yield and purity from TK. Rubber is formed in the roots of TK and exists in mostly solid form. Previously used mechanical processes extract NR from TK roots at low purity (< 90%) that does not meet industry standards (≥ 99.8%). To improve this, the effects of root chopping, enzymatic hydrolysis, pebble milling and alkaline pretreatment and purification on NR yield, purity and quality were investigated.RESULTSEnzymatic digestion (with and without alkaline pretreatment), yielded rubber at the highest yield (∼80%) and purity (99.4%). Alkaline pretreatment of roots improved NR yield and did not adversely affect quality. More rubber was extractable from chopped roots than whole roots, but the rubber was less pure. Alkaline purification of the extracted crude rubber further increased rubber purity but reduced rubber molecular weight.CONCLUSIONEnzymatic digestion with or without alkaline pretreatment forms the basis of aqueous processes that could be used for large‐scale, efficient extraction of TK rubber at high yield, purity and quality to meet industry standards for NR. © 2019 Society of Chemical Industry

Impact of triticale cultivar (× Triticosecale sp. Wittmack) and location on pretreatment requirements and fermentable sugars yield

Triticale, a man-made grain cereal developed by crossing wheat with rye and displaying high straw yield, has gained interest for second-generation fuel ethanol. This study aimed at assessing variability in straw properties from triticale cultivars grown in South Africa and their impact on straw processability for optimal yield of total fermentable sugars (TFS) from dilute acid pretreatment followed by enzymatic hydrolysis. Response surface methodology (RSM) was applied to maximize the total fermentable sugars yield from dilute acid pretreatment–enzymatic hydrolysis. The optimum pretreatment conditions 182 °C—0.39% (w/w)—15.4 min maximized total sugar yield at 50.5 g/100 g for straw from cultivar 01T43 (1.2% ash), representing total sugars recovery of 80.4% of theoretical TFS (xylose + glucose) in the straws. Conditions of 189 °C—0.60%—18 min and 190 °C—0.53%—13 min maximized total sugar yield for cultivars 00T207 (5.8% ash) and BACCHUS (4.4% ash) at 46.7 and 44.9 g/100 g which represented total sugars recoveries of 77.8 and 68% of theoretical TFS (xylose + glucose) in the straws, respectively. Enhancement of sugar yield from triticale straw is possible by dilute acid pretreatment optimization, coupled with selection of cultivars with low ash content in straw for reduced pretreatment requirements.

New Insight into Enzymatic Hydrolysis of the Rice Straw and Poplar: an In-depth Statistical Analysis on the Multiscale Recalcitrance

Certain substrate-related parameters that determine sugar release from pretreated lignocellulosic biomass are important for the biorefinery process optimization. Unfortunately, phylogenetical differences in plants often complicate physicochemical variances and mask mechanisms of biomass recalcitrance. Herein, an in-depth statistical approach that combines correlation analysis, principal component analysis, multiple linear regression, and multiscale validation procedures was employed to comprehensively analyze 14 compositional and structural parameters of cell wall collected after acid and base pretreatment. Individual and sequential analysis provided quantitative proof of lignin-relevant parameters as particular constraints for sugar release in two typical plants, the rice straw (Oryza sativa) and poplar (Populus girinensis). More striking contributions of lignin removal to xylose release were found in both biomasses, while the combination of crystallinity index (CrI) and CrI/glucan highlighted the specific hindrance of crystallinity of cellulose to glucose release. The compositional changes of lignin additionally affected glucose release in rice straw, while functional groups of lignin played a less pronounced role in poplar. The direct impacts of xylan removal and concomitant changes in biomass porosities insignificantly improved the sugar release. These results suggest that innate differences in diverse plants and the targeted sugar species should be considered when designing proper pretreatment for efficient enzymatic hydrolysis.

Facile fractionation of lignocelluloses by biomass-derived deep eutectic solvent (DES) pretreatment for cellulose enzymatic hydrolysis and lignin valorization

A recyclable and green biomass-derived deep eutectic solvent (DES) pretreatment was developed to deconstruct the recalcitrant structure ofEucalyptusfor further cellulose enzymatic saccharification and lignin valorization.

Microwave-assisted glucose production from bode (Styrax tonkinensis) woody biomass for bioethanol production

Microwave (MW)-assisted acid hydrolysis of lignocellulosic material derived from bode (Styrax tonkinensis) wood to glucose was performed to find effective uses for discarded chopsticks. The maximum amount of glucose produced by MW-assisted acid hydrolysis (from 1 g of untreated bode wood cellulose) was 0.48 g, and was obtained by heating at 200 °C for 1 min using 1.0% (w/w) sulfuric acid as catalyst. However, the maximum total glucose yield from both MW-assisted acid hydrolysis (0.16 g) and enzymatic hydrolysis of the treated residue (0.52 g) was 0.68 g, which was obtained at a microwave heating temperature of 180 °C for 5 min using 1.0% (w/w) sulfuric acid as catalyst. In conclusion, the results showed that microwave-assisted treatment at 200 °C using 1.0% (w/w) sulfuric acid as catalyst facilitated MW-assisted acid hydrolysis of bode wood cellulose and treatment at 180 °C served as pretreatment for enzymatic hydrolysis of the treated residue.

POTENCIAL BIOQUÍMICO DE METANO A PARTIR DE LA PAJA DE LA CAÑA DEAZÚCAR EN VERACRUZ, MÉXICO: COMBINANDO LOS PRETRATAMIENTOS DEAGUA CALIENTE E HIDRÓLISIS ENZIMÁTICA O BIOLÓGICA

Few studies have analysed the utilization of raw sugarcane straw (SCS) for biogas generation. It is important to highlight that these studies only report the biomethane potential (BMP) of the SCS, several form of pretreatment obtained low yields of biomethane compared to the highest BMP obtained here. This study presents data on improving Total BMP from SCS (378.80±0.11 ml CH4/g VSR), in order to lower the severity of the LHW (Liquid Hot Water) pretreatment and to enhance the efficiency of the enzymatic or biological hydrolysis pretreatment, two-step was employed, as follows: (LHW, 120° C, 1.5 bars, 31.25 gr SCS dry basis/L of reaction) with enzymatic hydrolysis (commercial cellulose ENMEX® at 20%) or biological hydrolysis (isolated lignocellulolytic bacteria 3.02 * 108 UFC/ml). This study found a higher BMP in the case of the biological hydrolysis treatment in comparison with the enzymatic one, 360.58 and 344.97 ml CH4/g VSR respectively. Furthermore, the alteration of the physicochemical composition and physical structure of SCS fibre was higher in the option combining LHW pretreatment and biological hydrolysis. This study can be useful as a future reference in Mexico for a scalable system, in order to assess its feasibility for biomethane generation as a sustainable source.

Improvement of enzymatic digestibility of wood by a sequence of optimized milling procedures with final vibratory tube mills for the amorphization of cellulose

AbstractA three-stage wood milling process was investigated leading to coarse, fine and amorphization of milled wood (MW) as a pretreatment for enzymatic wood hydrolysis. An eccentric vibratory tube mill (EVTM) and a spring suspended vibratory tube mill (SSVTM) were found to be suitable for wood cellulose amorphization. Both methods gave rise to highly digestible and amorphous wood powders amenable to enzymatic hydrolysis. The SSVTM had superior energy efficiency. The resulting MW afforded a 70% sugar yield via enzymatic hydrolysis and the total energy consumption was around 1.5 kWh kg−1oven-dried wood (odW) for all three milling stages. In contrast, EVTM consumed 17 kWh kg−1odW energy. Accordingly, SSVTM has a high potential for preparing wood for enzymatic hydrolysis.

Supercritical CO2 enzyme hydrolysis as a pretreatment for the release of isorhamnetin conjugates from Opuntia ficus-indica (L.) Mill

Isorhamnetin conjugates from Opuntia ficus-indica (L.) Mill (nopal) were obtained using enzymatic hydrolysis pretreatment under supercritical carbon dioxide (SC-CO2) conditions. Factorial designs and discriminate analysis were used to evaluate the influence of pressure, temperature, pH, time and aqueous ethanol solution on the total extraction yield and the isorhamnetin recovery using the enzymes Rapidase Maxi Fruit (RMF) and Viscozyme. Isorhamnetin triglycosides [isorhamnetin-3-O-glucosyl-rhamnosyl-rhamnoside (IG1) and isorhamnetin-3-O-glucosyl-rhamnosyl-pentoside (IG2)] and a diglycoside [isorhamnetin-3-O-glucosyl-rhmanoside (IG5)] were found in the extracts. The isorhamnetin profile pattern was dependent on the enzyme and process conditions used. The extract containing higher amounts of IG5 was the most potent inhibitor of nitric oxide reducing its production by 71.6±4.8%. Selective extraction of IG5 was achieved using RMF enzyme and optimal conditions determined by a response surface methodology. The use of enzyme under SC-CO2 conditions affected the release of isorhamnetin conjugate profiles which induced remarkable differences in the anti-inflammatory activity.

Evaluation of the main inhibitors from lignocellulose pretreatment for enzymatic hydrolysis and yeast fermentation

To produce cellulosic ethanol more economically, utilization of whole slurry of pretreated lignocellulose without separating liquid and solid fractions after thermal and/or chemical pretreatment of lignocellulose may be advantageous in terms of process economics. To carry out such processing on mixtures, which contain pretreatment byproducts, quantitative evaluation of the degree of inhibition of enzymatic hydrolysis and yeast fermentation by pretreatment byproducts are important. Therefore, in this study, the inhibitory effect of byproducts, focusing on sugar degradation products including furfural, hydroxymethylfurfural (HMF), acetic acid (AA), formic acid (FA), and levulinic acid (LA), on enzyme and microbial performance was investigated. The experimental conditions for SSF media containing the inhibitors were optimized by response-surface methodology-ridge analysis. The saccharification using commercial cellulase was most remarkably inhibited (approximately 28%) by HMF. The ethanol production by Saccharomyces cerevisiae was nearly completely inhibited (approximately 80%) by furfural. The toxicity was noted as HMF > FA > furfural > AA ≈ LA for enzymatic hydrolysis, and furfural > HMF > FA > AA > LA for yeast ethanol production. The results indicated that the inhibitor accumulation during pretreatment should be controlled for subsequent effective saccharification and fermentation.

A simply enzymatic hydrolysis pretreatment for β-mannanase production from konjac powder

Currently, the traditional fermentation using konjac powder for β-mannanase production presents operational difficulties and high energy consumption, because of the individual hot air sterilization for konjac powder. A simply enzymatic hydrolysis pretreatment for konjac powder was developed to solve the problems of the traditional process in a 7-L fermenter. In the new process, when hydrolysis yield of konjac powder was above 50%, the media became liquid state from gelatinous state and could be sterilized immediately, avoiding the hot air sterilization and solving the operational difficulties. Interestingly, the new process didn’t have negative influence on β-mannanase production. Additionally, it could save close to 23% of power consumption during the whole fermentation. For another example, it did work well using locust bean gum for β-mannanase production in a 7-L fermenter. Therefore, the new process might be scaled up for industrial production using mannan-based bioresource as substrate.

Comparison of alkaline and acid pretreatments for enzymatic hydrolysis of soybean hull and soybean straw to produce fermentable sugars

The specific characteristics of biomass structure and differences in chemical composition of soybean hull (SBH) and soybean straw (SBS) may result in different behavior of pretreatment and enzymatic hydrolysis. In this work, dilute sulfuric acid (DA) pretreatment and alkaline sodium hydroxide (AL) pretreatment in a range of pretreatment temperatures and durations were investigated to improve the enzymatic digestibility of SBH and SBS. Satisfactory enzymatic digestibility was observed in the hydrolysis of both pretreated soybean fractions, but SBH showed higher digestibility than that of SBS, no matter which pretreatment technology was applied. Furthermore, DA pretreatment was more effective than AL pretreatment in conversion of soybean fractions into fermentable sugars, if both pretreatment and enzymatic hydrolysis stages were considered. The highest total sugar yield of SBH and SBS using DA pretreatment and subsequently hydrolyzed with 30 FPU/g-DM cellulase were 86.9% and 70.3%, respectively.

Structural and Functional Characterization of TwoPennisetumsp. Biomass during Ultrasono-Assisted Alkali Pretreatment and Enzymatic Hydrolysis for Understanding the Mechanism of Targeted Delignification and Enhanced Saccharification

The recalcitrance offered by lignocellulose to get converted into simple sugars makes its conversion process complicated, hence pretreatment is required prior to enzymatic hydrolysis and fermentation. Ultrasonication-assisted alkali pretreatment (UA-NaOH) was found to be an effective pretreatment for delignification and enzymatic hydrolysis of denanath grass (DG) and hybrid napier grasses (HNG) in terms of maximum delignification and reducing sugar production. To determine the mechanism of pretreatment and enzymatic hydrolysis, the structural and functional characterization of native and pretreated grass biomass were investigated using SEM (scanning electron microscope), FT-IR (Fourier transformation infrared) spectroscopy, TGA (thermal gravimetric analysis), DSC (differential scanning) spectroscopy, and solid state 13C CP/MAS NMR (cross-polarization magic angle spinning nuclear magnetic resonance) spectroscopy. The surface erosions, distorted surface morphology and deconstruction of the cell wall compone...

Total glucose yield as the single response in optimizing pretreatments for Elaeis guineensis fibre enzymatic hydrolysis and its relationship with chemical composition of fibre

In this study, a new approach viz. total glucose yield (TGY) was used as the single response for the optimization of various pretreatments of oil palm (Elaeis guineensis) empty fruit bunch (EFB) fibre through response surface methodology. TGY was calculated by multiplying the enzymatic saccharification yield and pretreatment solid recovery yield. The optimum condition of each pretreatment was calculated based on the estimation model built and then verified experimentally. The optimum conditions for water, acid and alkali pretreatments were 170 °C for 30 min, 120 °C for 45 min in 2.0% (v/v) H2SO4 solution and 110 °C for 45 min in 3.0% (v/v) NaOH solution, respectively. Based on chemical composition analysis, although both the water and alkali pretreated EFB fibres exhibited more than 99% of the cellulose was converted into glucose, water pretreated fibre achieved the highest TGY, as it retained higher recovered glucose content. This study also verified that the use of TGY on the basis of original fibre weight was more appropriate than the enzymatic saccharification yield in the optimization study of biomass pretreatment, as it also considered the loss of the cellulose during pretreatments.

Noncatalytic Direct Liquefaction of Biorefinery Lignin by Ethanol

There is a growing interest in lignin valorization to biofuels and chemicals. Here, we propose a novel and simple noncatalytic process to directly liquefy lignin rich solid residual from second generation bioethanol production by solvolysis with ethanol. Through an extensive parameter study in batch autoclaves assessing the effects of varying reaction temperature, reaction time, and solvent:lignin ratio, it is shown that hydrothermally pretreated enzymatic hydrolysis lignin solvolysis in supercritical ethanol can produce a heptane soluble bio-oil without the need for exhaustive deoxygenation. The process does not require addition of catalyst or a reducing agent such as hydrogen. The process is advantageously carried out with a low reaction period (<1 h) and with a reduced amount of solvent to lignin feedstock (ethanol:lignin (w/w) ratio of 2:1) which is a previously unexplored domain for lignin solvolysis. The resulting bio-oil product is mainly a mixture of di- and monomeric lignin species where the orig...