Preparation of DES lignin-chitosan aerogel and its adsorption performance for dyes, catechin and epicatechin.

Herein, DES lignin was obtained by pretreatment of grapevine with a deep eutectic solvent (ChCl-LA). A novel chitosan-DES lignin composite aerogel material (CS-LIG aerogel) was prepared to adsorb methylene blue (MB), Congo red (CR), catechin (C), and epicatechin (EC). The CS-LIG aerogel was systematically characterized by modern technological instruments. It was demonstrated that the DES lignin was successfully incorporated and had an important effect on the morphological structure and adsorption of dyes and natural products in the aerogel. The adsorption kinetic models for both adsorbed CR and MB are pseudo-second-order models. Adsorption isotherms followed Langmuir for the adsorption of CR and Freundlich for the adsorption of MB. The π-π interaction and hydrogen bonding of DES lignin aromatic groups in CS-LIG aerogels were responsible for the adsorption of C and EC with 86.42 % and 90.85 % removal rates, respectively. This study opens a new avenue for the high-value utilization of DES lignin and the preparation of chitosan-based composites for the adsorption of dyes and purification of natural products.

High-solids enzymatic saccharification of starch-rich raw herbal biomass residues for producing high titers of glucose.

The bioresource utilization of herbal biomass residues (HBRs) has been receiving more attention. Herein, three different HBRs from Isatidis Radix (IR) and Sophorae Flavescentis Radix (SFR) and Ginseng Radix (GR) were subjected to batch and fed-batch enzymatic hydrolysis to produce high-concentration glucose. Compositional analysis showed the three HBRs had substantial starch content (26.36-63.29%) and relatively low cellulose contents (7.85-21.02%). Due to their high starch content, the combined action of cellulolytic and amylolytic enzymes resulted in greater release of glucose from the raw HBRs compared to using the individual enzyme alone. Batch enzymatic hydrolysis of 10% (w/v) raw HBRs with low loadings of cellulase (≤ 10 FPU/g substrate) and amylolytic enzymes (≤ 5.0 mg/g substrate) led to a high glucan conversion of ≥ 70%. The addition of PEG 6000 and Tween 20 did not contribute to glucose production. Furthermore, to achieve higher glucose concentrations, fed-batch enzymatic hydrolysis was conducted using a total solid loading of 30% (w/v). After 48-h of hydrolysis, glucose concentrations of 125 g/L and 92 g/L were obtained for IR and SFR residues, respectively. GR residue yielded an 83 g/L glucose concentration after 96 h of digestion. The high glucose concentrations produced from these raw HBRs indicate their potential as ideal substrate for a profitable biorefinery. Notably, the obvious advantage of using these HBRs is the elimination of the pretreatment step, which is typically required for agricultural and woody biomass in similar studies.

Cellulose esterification with carboxylic acid in deep eutectic solvent pretreatment inhibits enzymatic hydrolysis.

Avicel cellulose was pretreated using two commonly used carboxylic acid-based deep eutectic solvents, i.e., choline chloride-lactic acid and choline chloride-formic acid. The pretreatment process resulted in the formation of cellulose esters with lactic acid and formic acid, which was confirmed by infrared and nuclear magnetic resonance spectra. Surprisingly, the esterified cellulose led to a significant decrease in the 48-h enzymatic glucose yield (≥75%) compared to raw Avicel cellulose. Analysis of changes in cellulose properties caused by pretreatment, including crystallinity, degree of polymerization, particle size and cellulose accessibility, contradicted the observed decline in enzymatic cellulose hydrolysis. However, removing the ester groups through saponification largely recovered the reduction in cellulose conversion. The decreased enzymatic cellulose hydrolysis by esterification may be attributed to changes in the interaction between cellulose-binding domain of cellulase and cellulose. These findings provide valuable insights into improving the saccharification of lignocellulosic biomass pretreated by carboxylic acid-based DESs.

Acidic and alkaline deep eutectic solvents (DESs) pretreatment of grapevine: Component analysis, characterization, lignin structural analysis, and antioxidant properties.

Deep eutectic solvents (DESs) have been extensively applied to pretreat lignocellulose; however, comparative research on acidic and alkaline DES pretreatment is relatively lacking. Herein, pretreatment of grapevine agricultural by-products with seven DESs were compared in terms of removal of lignin and hemicellulose and component analysis of the pretreated residues. Among the tested DESs, both acidic choline chloride-lactic (CHCl-LA), and alkaline potassium carbonate-ethylene glycol (K2CO3-EG) were effective in delignification. Thereafter, the CHCl-LA and K2CO3-EG extracted lignin was compared by analyzing their physicochemical structure changes and antioxidant properties. The results showed that the thermal stability, molecular weight, and phenol hydroxyl percentage of CHCl-LA lignin were inferior to K2CO3-EG lignin. It was found that the high antioxidant activity of K2CO3-EG lignin was mainly attributed to the abundant phenol hydroxyl, guaiacyl (G), and para-hydroxy-phenyl (H). By comparing acidic and alkaline DES pretreatments and their lignin nuances in biorefining, novel insights are derived for the scheduling and selection of DES for lignocellulosic pretreatment.

Highly efficient glucose production from raw non-pretreated Chinese medicinal herbal residues via the synergism of cellulase and amylolytic enzymes.

Available literature on Chinese medicinal herbal residues (CMHRs) bioconversion highlights pretreatment prior to saccharification with cellulase without considering the presence of starch constituent. Herein, four commonly found CMHRs were tested for starch content, and it was found they all contained starch with content ranging from 4.74% to 16.78%. Hydrolysis of raw CMHRs with combined cellulase and amylolytic enzymes yielded increments of 16.85% to 26.51% in 48-h glucan conversion compared to cellulase alone. Further study showed 48-h glucan conversion of raw CMHRs outperformed that pretreated by water-ethanol successive extraction, ultrasound and acid, but underperformed alkali-pretreated CMHRs. Although increasing 48-h glucan conversion in the range of 7.40% to 24.10% compared to raw CMHRs, alkaline pretreatment demonstrated low glucose recovery and incurred additional cost, making it unfavorable. Saccharification of the four raw CMHRs with combined enzymes seems like a preferred option considering the elimination of high-cost pretreatment step.

Recent insights into greywater treatment: a comprehensive review on characteristics, treatment technologies, and pollutant removal mechanisms.

With the rapid socio-economic and industrial development, the problem of water shortage is becoming increasingly serious. Seeking alternative water sources to reduce the need for freshwater resources is an increasing concern. Household greywater production is high and accounts for about 50-80% of domestic wastewater. In recent years, the in situ treatment and reuse of greywater have received widespread attention. Treated greywater can be used for non-potable purposes such as toilet flushing and irrigation, which can greatly reduce the pressure of freshwater resource shortage. This paper reviews the sources and characteristics of greywater and analyzes its quantity and quality. In addition, this paper outlines and summarizes various greywater treatment technologies commonly used, including physical, biological, and chemical treatment technologies, as well as combination technologies. Understanding the mechanisms of contaminant removal is essential for effective greywater treatment. While discussing different treatment technologies, we focus on the removal mechanisms of pollutants from greywater, including organics, nutrients, surfactants, and emerging contaminants. Finally, future perspectives on greywater management and reuse are presented. Through a comprehensive review, we expect that this review will help the reader to better understand the characteristics of greywater and to more rationally select the appropriate treatment technology based on the removal mechanism of pollutants.

Structure-property-performance relationships of lactic acid-based deep eutectic solvents with different hydrogen bond acceptors for corn stover pretreatment.

Herein, ten types of lactic acid-based deep eutectic solvents (DESs) with differently structured hydrogen bond acceptors (HBAs) were used for corn stover pretreatment. Among the tested DESs, those composed of HBAs with short alkyl chain were more effective to remove lignin and xylan, resulting in higher enzymatic digestion of the pretreated solids than their counterparts with long alky chain. Also, functional groups of HBAs demonstrated significant effects on biomass deconstruction. In order to interpret the different pretreatment performance of the tested DESs, Kamlet-Taft solvent polarity parameters of the tested DESs were correlated to their lignocellulose pretreatment performance. It was found that hydrogen bond acidity (Kamlet-Taft α parameter) had strong positive relationships with pretreatment efficacy of the studied DESs. These findings not only clarified the structure-property-performance relationships of the DESs, but also provided novel insights into design and selection of DESs for lignocellulose pretreatment.

Comparison of Corn Stover Pretreatments with Lewis Acid Catalyzed Choline Chloride, Glycerol and Choline Chloride-Glycerol Deep Eutectic Solvent.

Herein, corn stover (CS) was pretreated by less corrosive lewis acid FeCl3 acidified solutions of neat and aqueous deep eutectic solvent (DES), aqueous ChCl and glycerol at 120 °C for 4 h with single FeCl3 pretreatment as control. It was unexpected that acidified solutions of both ChCl and glycerol were found to be more efficient at removing lignin and xylan, leading to higher enzymatic digestibility of pretreated CS than acidified DES. Comparatively, acidified ChCl solution exhibited better pretreatment performance than acidified glycerol solution. In addition, 20 wt% water in DES dramatically reduced the capability of DES for delignification and xylan removal and subsequent enzymatic cellulose saccharification of pretreated CS. Correlation analysis showed that enzymatic saccharification of pretreated CS was highly correlated to delignification and cellulose crystallinity, but lowly correlated to xylan removal. Recyclability experiments of different acidified pretreatment solutions showed progressive decrease in the pretreatment performance with increasing recycling runs. After four cycles, the smallest decrease in enzymatic cellulose conversion (22.07%) was observed from acidified neat DES pretreatment, while the largest decrease (43.80%) was from acidified ChCl pretreatment. Those findings would provide useful information for biomass processing with ChCl, glycerol and ChCl-glycerol DES.

One step open fermentation for lactic acid production from inedible starchy biomass by thermophilic Bacillus coagulans IPE22.

The aim of this study was to establish a simplified operational process for lactic acid (LA) production by Bacillus coagulans IPE22 from inedible starchy biomass with open fermentation method. First, 29.47 mU/mg specific amylase activity was detected in direct batch fermentation from soluble starch, but the activity of the produced amylase was too low for effective production of LA. Then seven batches from 72 g/L soluble starch were conducted without sterilization. It was found that one step simultaneous liquefaction, saccharification and fermentation (SLSF) with the addition of mesothermal α-amylase and glucoamylase was the optimal mode with LA concentration, yield and productivity of 68.72 g/L, 0.99 g/g and 1.72 g/L h respectively. Finally, inedible starchy biomass, cassava and sorghum flours, were proved to be alternatives to refined soluble starch. For the first time, one step open SLSF of inedible starchy biomass was reported for LA production by B. coagulans.

Immobilization of cellulase on a core-shell structured metal-organic framework composites: Better inhibitors tolerance and easier recycling.

For the first time, cellulase was successfully immobilized on a magnetic core-shell metal-organic framework (MOF) material, UIO-66-NH2. The as-prepared immobilized cellulase demonstrated a high protein loading efficiency of 126.2 g/g support and a high enzyme activity recovery of 78.4%. Cellulase immobilized on magnetic UIO-66-NH2 exhibited a superior performance in terms of pH stability, thermal stability and catalytic efficiency compared to its free form. Notably, immobilized cellulase could be recycled for up to 5 consecutive runs. Furthermore, compared to free cellulase, immobilized cellulase showed better tolerance to formic acid and vanillin, two typical inhibitors found in lignocellulosic prehydrolysates. In the presence of 5 g/L of formic acid and vanillin, immobilized cellulase demonstrated 16.8% and 21.5% higher activity than free enzyme, respectively, and its improvement in hydrolysis yield was 18.7% and 19.6% respectively. This is firstly confirmed that immobilization can alleviate the inhibitory effects of certain pretreatment inhibitors on cellulase.

Improving the hydrolysis efficiency of soy sauce residue using ultrasonic probe-assisted enzymolysis technology.

Ultrasonic probe-assisted enzymolysis technology was developed to improve the hydrolysis efficiency of soy sauce residue (SSR). The effects of enzyme type and enzymatic hydrolysis parameters on the hydrolysis degree of SSR were studied firstly to obtain the optimal enzymatic hydrolysis conditions. Then the effects of ultrasound on protease activity and structure of SSR were investigated to elucidate the acting mechanism of ultrasound. Finally, the ultrasonic-assisted enzymatic hydrolysis modes were designed and compared, and the hydrolysates from SSR were characterized to evaluate their further application. The results showed that a hydrolysis degree of 15.53% could be obtained under the optimum enzymolysis conditions: enzyme amount 6000U/g, pH 7.8, temperature 50°C, the ratio of substrate to water phase 1:20, hydrolysis time 4h. Increasing ultrasound treatment time or power could reduce substrate size and consequently enhance the catalytic surface area. Prolonging ultrasound treatment time had a negative influence on enzyme activity, but low ultrasound power was helpful for increasing the enzyme activity. Ultrasound pretreatment of SSR followed by enzymatic hydrolysis increased the hydrolysis degree by 47.6%. When the ultrasound was applied directly to enzymolysis process, the hydrolysis degree of SSR exhibited an increase of 33.0%. The hydrolysates from SSR exhibited good antioxidant activities, and had a potential use as a functional ingredient in food or feed industry.

Effect of alkali lignins with different molecular weights from alkali pretreated rice straw hydrolyzate on enzymatic hydrolysis.

This study investigated the effect of alkali lignins with different molecular weights on enzymatic hydrolysis of lignocellulose. Different alkali lignins fractions, which were obtained from cascade ultrafiltration, were added into the dilute acid pretreated (DAP) and alkali pretreated (AP) rice straws respectively during enzymatic hydrolysis. The results showed that the addition of alkali lignins enhanced the hydrolysis and the enhancement for hydrolysis increased with increasing molecular weights of alkali lignins, with maximum enhancement being 28.69% for DAP and 20.05% for AP, respectively. The enhancement was partly attributed to the improved cellulase activity, and filter paper activity increased by 18.03% when adding lignin with highest molecular weight. It was found that the enhancement of enzymatic hydrolysis was correlated with the adsorption affinity of cellulase on alkali lignins, and the difference in surface charge and hydrophobicity of alkali lignins were responsible for the difference in affinity between cellulase and lignins.

Inhibitory effect of vanillin on cellulase activity in hydrolysis of cellulosic biomass.

Pretreatment of lignocellulosic material produces a wide variety of inhibitory compounds, which strongly inhibit the following enzymatic hydrolysis of cellulosic biomass. Vanillin is a kind of phenolics derived from degradation of lignin. The effect of vanillin on cellulase activity for the hydrolysis of cellulose was investigated in detail. The results clearly showed that vanillin can reversibly and non-competitively inhibit the cellulase activity at appropriate concentrations and the value of IC50 was estimated to be 30 g/L. The inhibition kinetics of cellulase by vanillin was studied using HCH-1 model and inhibition constants were determined. Moreover, investigation of three compounds with similar structure of vanillin on cellulase activity demonstrated that aldehyde group and phenolic hydroxyl groups of vanillin had inhibitory effect on cellulase. These results provide valuable and detailed information for understanding the inhibition of lignin derived phenolics on cellulase.

Efficient production of acetone-butanol-ethanol (ABE) from cassava by a fermentation-pervaporation coupled process.

Production of acetone-butanol-ethanol (ABE) from cassava was investigated with a fermentation-pervaporation (PV) coupled process. ABE products were in situ removed from fermentation broth to alleviate the toxicity of solvent to the Clostridium acetobutylicum DP217. Compared to the batch fermentation without PV, glucose consumption rate and solvent productivity increased by 15% and 21%, respectively, in batch fermentation-PV coupled process, while in continuous fermentation-PV coupled process running for 304 h, the substrate consumption rate, solvent productivity and yield increased by 58%, 81% and 15%, reaching 2.02 g/Lh, 0.76 g/Lh and 0.38 g/g, respectively. Silicalite-1 filled polydimethylsiloxane (PDMS)/polyacrylonitrile (PAN) membrane modules ensured media recycle without significant fouling, steadily generating a highly concentrated ABE solution containing 201.8 g/L ABE with 122.4 g/L butanol. After phase separation, a final product containing 574.3g/L ABE with 501.1g/L butanol was obtained. Therefore, the fermentation-PV coupled process has the potential to decrease the cost in ABE production.

Improving lactic acid productivity from wheat straw hydrolysates by membrane integrated repeated batch fermentation under non-sterilized conditions.

Bacillus coagulans IPE22 was used to produce lactic acid (LA) from mixed sugar and wheat straw hydrolysates, respectively. All fermentations were conducted under non-sterilized conditions and sodium hydroxide was used as neutralizing agent to avoid the production of insoluble CaSO4. In order to eliminate the sequential utilization of mixed sugar and feedback inhibition during batch fermentation, membrane integrated repeated batch fermentation (MIRB) was used to improve LA productivity. With MIRB, a high cell density was obtained and the simultaneous fermentation of glucose, xylose and arabinose was successfully realized. The separation of LA from broth by membrane in batch fermentation also decreased feedback inhibition. MIRB was carried out using wheat straw hydrolysates (29.72 g/L glucose, 24.69 g/L xylose and 5.14 g/L arabinose) as carbon source, LA productivity was increased significantly from 1.01 g/L/h (batch 1) to 2.35 g/L/h (batch 6) by the repeated batch fermentation.

An efficient process for lactic acid production from wheat straw by a newly isolated Bacillus coagulans strain IPE22.

A thermophilic lactic acid (LA) producer was isolated and identified as Bacillus coagulans strain IPE22. The strain showed remarkable capability to ferment pentose, hexose and cellobiose, and was also resistant to inhibitors from lignocellulosic hydrolysates. Based on the strain's promising features, an efficient process was developed to produce LA from wheat straw. The process consisted of biomass pretreatment by dilute sulfuric acid and subsequent SSCF (simultaneous saccharification and co-fermentation), while the operations of solid-liquid separation and detoxification were avoided. Using this process, 46.12 g LA could be produced from 100g dry wheat straw with a supplement of 10 g/L corn steep liquid powder at the cellulase loading of 20 FPU (filter paper activity units)/g cellulose. The process by B. coagulans IPE22 provides an economical route to produce LA from lignocellulose.

Recycling cellulase from enzymatic hydrolyzate of acid treated wheat straw by electroultrafiltration.

This work explores the feasibility of recycling cellulase by electroultrafiltration (EUF), an ultrafiltration process enhanced by an electric field, to reduce the cost of enzymatic transformation of cellulose. The effect of electric field under different operating conditions (buffer concentration, acid treated wheat straw concentration, current and temperature) on flux during EUF was examined. The results showed that EUF was effective to reduce concentration polarization (CP) and enhance filtration flux in recycling cellulase. The flux improvement by the electric field could be strengthened at low buffer concentration (5 mM) and relatively low temperature (room temperature) and high current (150 mA). The flux for 2% (substrate concentration, w/v) lignocellulosic hydrolyzate increased by a factor of 4.4 at 836 V/m and room temperature, compared to that without electric field. This work shows that under appropriate operating conditions EUF can efficiently recycle cellulase from lignocellulosic hydrolyzate and thus substantially reduce hydrolysis cost.

Intensification of ß-poly(L: -malic acid) production by Aureobasidium pullulans ipe-1 in the late exponential growth phase.

ß-Poly(malic acid) (PMLA) has attracted industrial interest because this polyester can be used as a prodrug or for drug delivery systems. In PMLA production by Aureobasidium pullulans ipe-1, it was found that PLMA production was associated with cell growth in the early exponential growth phase and dissociated from cell growth in the late exponential growth phase. To enhance PMLA production in the late phase, different fermentation modes and strategies for controlling culture redox potential (CRP) were studied. The results showed that high concentrations of produced PMLA (above 40 g/l) not only inhibited PMLA production, but also was detrimental to cell growth. Moreover, when CRP increased from 57 to 100 mV in the late exponential growth phase, the lack of reducing power in the broth also decreased PMLA productivity. PMLA productivity could be enhanced by repeated-batch culture to maintain cell growth in the exponential growth phase, or by cell-recycle culture with membrane to remove the produced PMLA, or by maintaining CRP below 70 mV no matter which kind of fermentation mode was adopted. Repeated-batch culture afforded a high PMLA concentration (up to 63.2 g/l) with a productivity of 1.15 g l(-1) h(-1). Cell-recycle culture also confirmed that PMLA production by the strain ipe-1 was associated with cell growth.

Application of ultrafiltration and nanofiltration for recycling cellulase and concentrating glucose from enzymatic hydrolyzate of steam exploded wheat straw.

Application of combined ultrafiltration (UF) and nanofiltration (NF) was examined to recycle cellulase and concentrate glucose present in lignocellulosic hydrolyzate. With PES10 membrane operated at 25.6 l/m(2) h, 73.9% of cellulase protein present in the hydrolyzate suspension could be recovered while allowing free transmission of glucose. The permeate obtained from UF was then concentrated by NF. With NF270 membrane operated at 13.3 l/m(2) h, the glucose concentration in the ultrafiltered hydrolyzate increased from 30.2 to 110.2 g/l. Recycling cellulase by UF could reduce the hydrolysis cost of lignocellulosic feedstock, while concentrating glucose by NF could improve the fermentation efficiency of lignocellulosic hydrolyzate and lower the separation and purification cost of fermentative product. Therefore, the use of UF and NF for treating lignocellulosic hydrolyzate could be a promising approach in fermentative production of bioproducts and biofuels using lignocellulosic feedstock as substrate.

A two-stage ultrafiltration and nanofiltration process for recycling dairy wastewater.

A two-stage ultrafiltration and nanofiltration (UF/NF) process for the treatment of model dairy wastewater was investigated to recycle nutrients and water from the wastewater. Ultracel PLGC and NF270 membranes were found to be the most suitable for this purpose. In the first stage, protein and lipid were concentrated by the Ultracel PLGC UF membrane and could be used for algae cultivation to produce biodiesel and biofuel, and the permeate from UF was concentrated by the NF270 membrane in the second stage to obtain lactose in retentate and reusable water in permeate, while the NF retentate could be recycled for anaerobic digestion to produce biogas. With this approach, most of dairy wastewater could be recycled to produce reusable water and substrates for bioenergy production. Compared with the single NF process, this two-stage UF/NF process had a higher efficiency and less membrane fouling.