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Chloroform is a toxic and persistent solvent that cannot be effectively removed from the environment by actual remediation methods. Chloroform removal using persulfate activated by iron nanoparticles has been tested but is limited by chloroform inertness and nanoparticle inactivation in the real environment. Here we hypothesized that tannic acid could improve the activation of persulfate with Fe/Ni nanoparticles. We studied the influence of tannic acid/Fe ratio, persulfate concentration, initial pH, temperature, inorganic anions and natural organic matters on chloroform removal. We found that tannic acid-Fe/Ni-persulfate system with 1.65 mol% of tannic acid-Fe and 3.2 mM of persulfate yielded about 87–97% chloroform removal in the 2.9–10.7 pH range. Electron paramagnetic resonance and radical quenching experiments revealed that SO4•− and •OH were primarily responsible for chloroform removal. High removal is probably due to Fe-tannic acid chelation that prevents the precipitation of iron hydroxide on Fe/Ni nanoparticles, thus preserving active sites.

Chloroform is an harmful chlorinated hydrocarbon which is hardly degraded using actual dechlorination methods. Alternatively, carboxymethyl cellulose/zero-valent iron appears promising to degrade chlorinated hydrocarbons in water, yet actually carboxymethyl cellulose cannot inhibit the oxidation and sedimentation of iron ions under alkaline condition. Here, polyethylene glycol, a green and low-cost non-ionic polymer, was used as a stabilizer to synthesize polyethylene glycol-stabilized Fe/Ni nanoparticles (PEG-Fe/Ni) for removing chloroform from water in a wide range of pH, from 3 to 11. PEG-Fe/Ni was prepared by a stepwise liquid-phase chemical reduction, then added into groundwater to remove chloroform. Results show that polyethylene glycol can both reduce the particle size from 106.9 to 79.6 nm and prevent the oxidation and sedimentation of iron ions under alkaline condition. The removal efficiency of chloroform increased from 86.3 to 100% at pH 6 in the presence of polyethylene glycol, and slightly decreased to 95.4% at pH 11. The calculated rate constant (k) indicates that chloroform removal follows pseudo-first-order kinetics. Furthermore, the PEG-Fe/Ni also removed chloroform from real groundwater at pH 8 with an efficiency of 90.1% in 4 h, which is higher than that for Fe/Ni nanoparticles, of 41.7%.

Pollution of waters by chlorinated organic pollutants is difficult to clean using actual remediation methods because these pollutants are highly stable. For instance, chloroform (CHCl3) is poorly reactive with common oxidants such as iron-activated persulfate, ozone and Fenton’s reagents. Therefore, there is a need to develop new oxidants. Here, we designed a new dechlorination system, in which tannic acid and NaOH work synergistically to activate persulfate. We tested the effect of temperature and concentrations of persulfate, NaOH and tannic acid, on chloroform removal from water. Free radical-quenching experiments were performed to identify active species. Results show that chloroform removal increased from 42.5 to 97.6 wt.% after the addition of 300 mg/L tannic acid in 0.4 M NaOH. Superoxide radicals (O 2 ·− ) was primarily responsible for the degradation of chloroform in the persulfate/NaOH/tannic acid system, in which tannic acid reacts with persulfate to produce hydroperoxide. Hydroperoxide then reduces persulfate to generate sulfate radicals (SO4·−), and produces O 2 ·− . NaOH-activated persulfate produces hydroxyl radicals (HO·), which can oxidize chloroform. This dechlorination system showed excellent degradation efficiency for recalcitrant halogenated compounds, making it a very promising candidate for practical applications.

We investigated the effects of ultrasound treatment on cellulase adsorption and lignocellulose hydrolysis. The activity of cellulase remained constant upon low-power ultrasound treatment ( 280 W). Oscillating cellulase adsorption occurred upon ultrasound treatment with any intensity. The maxima for desorption and adsorption were 41.9 and 83.1%, respectively, during 1 h of 90 W ultrasound treatment at 50 °C. A comparison between the short-time with long-time ultrasound experiments indicated that ultrasound treatment tended to desorb cellulase from substrate. However, ultrasound treatment also led to further surface erosion of biomass, which increased cellulase accessibility. These joint actions of ultrasound treatment induced the oscillating adsorption of cellulase. The increase in cellulase accessibility caused by ultrasound treatment led to a significant enhancement in lignocellulose hydrolysis.

Background Biological pretreatment is an environmentally safe method for disrupting recalcitrant structures of lignocellulose and thereby improving their hydrolysis efficiency. Expansin and expansin-like proteins act synergistically with cellulases during hydrolysis. A systematic analysis of the adsorption behavior and mechanism of action of expansin family proteins can provide a basis for the development of highly efficient pretreatment methods for cellulosic substrates using expansins. Results Adsorption of Bacillus subtilis expansin (BsEXLX1) onto cellulose film under different conditions was monitored in real time using a quartz crystal microbalance with dissipation. A model was established to describe the adsorption of BsEXLX1 onto the film. High temperatures increased the initial adsorption rate while reducing the maximum amount of BsEXLX1 adsorbed onto the cellulose. Non-ionic surfactants (polyethylene glycol 4000 and Tween 80) at low concentrations enhanced BsEXLX1 adsorption; whereas, high concentrations had the opposite effect. However, sodium dodecyl sulfate inhibited adsorption at both low and high concentrations. We also investigated the structural changes of cellulose upon BsEXLX1 adsorption and found that BsEXLX1 adsorption decreased the crystallinity index, disrupted hydrogen bonding, and increased the surface area of cellulose, indicating greater accessibility of the substrate to the protein. Conclusions These results increase our understanding of the interaction between expansin and cellulose, and provide evidence for expansin treatment as a promising strategy to enhance enzymatic hydrolysis of lignocellulose. Electronic supplementary material The online version of this article (10.1186/s13068-018-1318-2) contains supplementary material, which is available to authorized users.

The aim of this work was to develop an alginate-casein composite microsphere as a bioactive vehicle for oral administration of nutrients by a simple extrusion dripping method. Riboflavin was selected as a model drug, and the microencapsulation efficiency was raised to 97.94% after optimizing the preparation conditions by response surface methodology. In vitro release studies showed that riboflavin was released completely from alginate-casein microspheres in simulated intestinal fluids. Meanwhile, the morphology, structure and interaction between alginate and casein were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectra.

A fast and facile method of fabricating fiber-optic localized surface plasmon resonance sensors based on spherical gold nanoparticles was introduced in this study. The gold nanoparticles with an average diameter of 55 nm were synthesized via the Turkevich method and were then immobilized onto the surface of an uncladded sensor probe using a polydopamine layer. To obtain a sensor probe with high sensitivity to changes in the refractive index, a set of key optimization parameters, including the sensing length, coating time of the polydopamine layer, and coating time of the gold nanoparticles, were investigated. The sensitivity of the optimized sensor probe was 522.80 nm per refractive index unit, and the probe showed distinctive wavelength shifts when the refractive index was changed from 1.328 6 to 1.398,7. When stored in deionized water at 4 °C, the sensor probe proved to be stable over a period of two weeks. The sensor also exhibited advantages, such as low cost, fast fabrication, and simple optical setup, which indicated its potential application in remote sensing and real-time detection.

Recycling of cellulases is an effective way to reduce the cost of enzymatic hydrolysis for the production of cellulosic ethanol. In this study, we examined the adsorption and desorption behaviors of cellulase at different pH values and temperatures. Furthermore, we developed a promising way to recover both free and bound cellulases by pH-triggered adsorption-desorption. The results show that acidic pH (e.g., pH 4.8) was found to favor adsorption, whereas alkaline pH (e.g., pH 10) and low temperature (4-37 °C) favored desorption. The adsorption of cellulases reached an equilibrium within 60 min at pH 4.8 and 25 °C, leading to approximately 50 % of the added cellulases bound to the substrate. By controlling the pH of eluent (citrate buffer, 25 °C), we were able to increase the desorption efficiency of bound cellulases from 15 % at pH 4.8 to 85 % at pH 10. To recover cellulases after enzymatic hydrolysis, we employed adsorption by fresh substrate and desorption at pH 10 to recover the free cellulases in supernatant and the bound cellulases in residue, respectively. The recycling performance (based on the glucose yield) of this simple strategy could reach near 80 %. Our results provided a simple, low-cost, and effective approach for cellulase recycling during the enzymatic hydrolysis of lignocellulosic biomass.

We report a new approach to constructing a peptide–polysaccharide hybrid hydrogel via the calcium-ion-triggered co-assembly of fluorenylmethyloxycarbonyl-diphenylalanine (Fmoc-FF) peptide and alginate. Calcium ions triggered the self-assembly of Fmoc-FF peptide into nanofibers with diameter of about 30 nm. Meanwhile, alginate was rapidly crosslinked by the calcium ions, leading to the formation of stable hybrid hydrogel beads. Compared to alginate or Fmoc-FF hydrogel alone, the hybrid Fmoc-FF/alginate hydrogel had much better stability in both water and a phosphate-buffered solution (PBS), probably because of the synergistic effect of noncovalent and ionic interactions. Furthermore, docetaxel was chosen as a drug model, and it was encapsulated by hydrogel beads to study the in vitro release behavior. The sustained and controlled docetaxel release was obtained by varying the concentration ratio between Fmoc-FF peptide and alginate.

Acid-catalyzed dehydration of carbohydrates into 5-hydroxymethylfurfural (HMF), a valuable biomass-derived intermediate, has received increasing attention. Efficient methods for HMF production are needed for successful commercialization of HMF in the near future. A new process for the dehydration of sugars into 5-hydroxymethylfurfural in aqueous/butanol media enhanced by using formic acid was developed. The effects of formic acid concentration, reaction temperature, and reaction time on the fructose conversion and HMF yield showed the significant influences of these process variables. The optimum conditions were found to be 2.5 mol/L formic acid concentration, 170°C and 70 min. Under such conditions, a fructose conversion of 98.3% with a HMF yield of 69.2% was achieved. The application of the butanol solvent and formic acid led to the conversion of fructose to HMF with high yield. The catalytic system in this study has prospects for commercial application due to its less corrosion and convenient downstream separation.

Biofuels produced from lignocellulosic biomass can significantly reduce the energy dependency on fossil fuels and the resulting effects on environment. In this respect, cellulosic ethanol as an alternative fuel has the potential to become a viable energy source in the near future. Over the past few decades, tremendous effort has been undertaken to make cellulosic ethanol cost competitive with conventional fossil fuels. The pretreatment step is always necessary to deconstruct the recalcitrant structures and to make cellulose more accessible to enzymes. A large number of pretreatment technologies involving physical, chemical, biological, and combined approaches have been developed and tested at the pilot scale. Furthermore, various strategies and methods, including multi-enzyme complex, non-catalytic additives, enzyme recycling, high solids operation, design of novel bioreactors, and strain improvement have also been implemented to improve the efficiency of subsequent enzymatic hydrolysis and fermentation. These technologies provide significant opportunities for lower total cost, thus making large-scale production of cellulosic ethanol possible. Meanwhile, many researchers have focused on the key factors that limit cellulose hydrolysis, and analyzing the reaction mechanisms of cellulase. This review describes the most recent advances on process intensification and mechanism research of pretreatment, enzymatic hydrolysis, and fermentation during the production of cellulosic ethanol.

A facile one-pot approach for synthesis of gold nanoparticles with narrow size distribution and good stability was presented by reducing chloroauric acid with a polysaccharide, konjac glucomannan (KGM) in alkaline solution, which is green and economically viable. Here, KGM served both as reducing agent and stabilizer. The effects of KGM on the formation and stabilization of as-synthesized gold nanoparticles were studied systematically by a combination of UV-visible (UV-vis) absorption spectroscopy, transmission electron microscopy, X-ray diffraction, dynamic light scattering, and Fourier transform infrared spectroscopy. Furthermore, the gold nanoparticles exhibited a notable catalytic activity toward the reduction of 4-nitrophenol to 4-aminophenol.