Wheat flour-derived amyloid fibrils for efficient removal of organic dyes from contaminated water.

Amyloid fibrils derived from different proteins have been proved as a promising material for adsorption of various pollutants from wastewater, which showed advantages of low cost and eco-friendliness. However, most of the amyloid fibrils derived from animal-based proteins with high environmental footprint, while more sustainable amyloid fibrils derived from plant materials are desirable. In this study, a plant-derived amyloid fibril was extracted from the commonly used wheat flour with a simple and scalable protein purification and fibrillization process. Interestingly, the amyloid fibrils showed good adsorption capacity towards typical organic dyes (Eosin Y (EY) and Congo red (CR)) from contaminated water. Adsorption kinetic analysis indicated the adsorption process to EY or CR by wheat flour amyloid well fitted with a pseudo-second-order model. The adsorption also followed a Langmuir isothermal model with adsorption capacities of 333 mg/g and 138 mg/g towards CR and EY, respectively. This work demonstrated the feasibility to utilize the plant-based amyloid fibril for organic dyes removal from contaminated water, which provided an affordable, sustainable and scalable tool for organic dyes removal from wastewater.

Extracellular Electrons Powered Microbial CO2 Upgrading: Microbial Electrosynthesis and Artificial Photosynthesis.

Microbial CO2 upgrading featured with mild operating condition and low energy consumption is one of the preferred choices with the goal of carbon-neutral economy. Some innovative biotechnology platforms based on those microorganisms having characteristic of taking up extracellular electrons are being developed to accomplish the CO2-to-chemical/fuel conversion, especially microbial electrosynthesis (MES) and artificial photosynthetic biohybrid system (PBS). The MES wherein microbial catalysts are capable of converting CO2 into value-added biochemicals and biofuels by directly utilizing an electrode (cathode) as the sole electron donor with high energy efficiency has attracted widespread attention since its inception 10 years ago. Despite substantial progress in bench scale, such technology is still not economically competitive enough for industrialization on account of its low-value products and poor productivity. Nevertheless, the rational construction of electrodes and genetic engineering of producing strains promise to solve these bottlenecks, which will be discussed adequately in this chapter. Furthermore, the PBS that couples microbial cell factories with inorganic nanomaterials capable of light harvesting has also been invented as an up-and-coming alternative to direct solar-to-chemical conversion beyond natural photosynthesis. Although still in the conceptual stage, evidence shows that the PBS achieves higher overall energy efficiency than natural photosynthesis of plants and crops for CO2-fixation, which is also discussed. The microbial feature of extracellular electron uptake from either renewable electricity or photoelectrons brings many promising possibilities to the CO2 bio-upgrading technologies, while the development of high-performance components and coordinated optimization of reaction systems are necessary for these technologies to move from the laboratory to the industrialization.

Highly thermostable GH51 α-arabinofuranosidase from Hungateiclostridium clariflavum DSM 19732.

Arabinofuranosidase plays an essential role in the process of hydrolysis of arabinoxylan (AX). Thermostable, versatile, and efficient arabinofuranosidase is thus of great interest for the biorefinery industry. A GH51 arabinofuranosidase, Abf51, from Hungateiclostridium clariflavum DSM 19732 was heterogeneously expressed in Escherichia coli. Abf51 was found to have an optimal pH and temperature of 6.5 and 60 °C, respectively, with very high thermostability. At the optimal working temperature (60 °C), Abf51 retained over 90% activity after a 2-day incubation and over 60% activity after a 6-day incubation. Abf51 could effectively remove the arabinofuranosyls from three kinds of AX oligosaccharides [23-α-L-arabinofuranosyl-xylotriose (A2XX), 32-α-L-arabinofuranosyl-xylobiose (A3X), and 2333-di-α-L-arabinofuranosyl-xylotriose (A2 + 3XX)], which characterized as either single substitution or double substitution by arabinofuranosyls on terminal xylopyranosyl units. The maximal catalytic efficiency (Kcat/Km) was observed using p-nitrophenyl-α-L-arabinofuranoside (pNPAF) as a substrate (205.0 s-1 mM-1), followed by using A3X (22.8 s-1 mM-1), A2XX (6.9 s-1 mM-1), and A2 + 3XX (0.5 s-1 mM-1) as substrates. Moreover, the presence of Abf51 significantly stimulated the saccharification level of AX (18.5 g L-1) up to six times along with a ß-xylanase as well as a ß-xylosidase. Interestingly, in our survey of top thermostable arabinofuranosidases, most members were found from GH51, probably due to their owning of (ß/α)8-barrel architectures. Our results suggested the great importance of GH51s as candidates for thermostable, versatile, and efficient arabinofuranosidases toward industry application.

Characterization of a laccase from a wood-feeding termite, Coptotermes formosanus.

Coptotermes formosanus Shiraki is a wood-feeding termite which secretes a series of lignolytic and cellulolytic enzymes for woody biomass degradation. However, the lignin modification mechanism in the termite is largely elusive, and the characteristics of most lignolytic enzymes in termites remain unknown. In this study, a laccase gene lac1 from C. formosanus was heterogeneously expressed in insect Sf9 cells. The purified Lac1 showed strong activities toward hydroquinone (305 mU/mg) and 2,6-dimethoxyphenol (2.9 mU/mg) with low Km values, but not veratryl alcohol or 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid). Lac1 could function well from pH 4.5 to 7.5, and its activity was significantly inhibited by H2 O2 at above 4.85 mmol/L (P < 0.01). In addition, the lac1 gene was found to be mainly expressed in the salivary glands and foregut of C. formosanus, and seldom in the midgut or hindgut. These findings suggested that Lac1 is a phenol-oxidizing laccase like RflacA and RflacB from termite Reticulitermes flavipes, except that Lac1 was found to be more efficient in phenol oxidation, and it did not require H2 O2 for its function. It is suspected that this kind of termite laccase might only be able to directly oxidize low redox-potential substrates, and the high redox-potential groups in lignin might be oxidized by other enzymes in the termite or by using the Fenton reaction.

Adsorption and removal of triphenylmethane dyes from water by magnetic reduced graphene oxide.

Triphenylmethane (TPM) dye is one of the most prevalent and recalcitrant water contaminants. Magnetic reduced graphene oxide (rGO) is an efficient adsorbent for organic pollutants removal. However, the performance and adsorption kinetics of magnetic rGO towards TPM have not yet been studied. In this study, a magnetic Fe3O4@rGO nano-composite, which could be easily removed from water with a simple magnetic separation step was synthesized and characterized. The magnetic rGO showed fast adsorption rate and high adsorption capacity towards different TPM dyes (the Langmuir monolayer adsorption capacity is 64.93 mg/g for adsorption of crystal violet). The adsorption processes are well-fitted to the pseudo-second-order kinetic model (R(2) > 0.99) and the Langmuir isotherm model (R(2) = 0.9996). Moreover, the magnetic rGO also showed excellent recycling and regeneration capabilities. The results indicated that adsorption with magnetic rGO would be a promising strategy to clean up the TPM contamination.

Increase in enzyme accessibility by generation of nanospace in cell wall supramolecular structure.

An energy efficient nanofibrillation method that combines disk milling and mild hot-compressed water (HCW) treatment was developed to improve enzymatic accessibility of Eucalyptus wood. In this method, the residual product of HCW treatment was fibrillated by disk milling under wet conditions. Relatively moderate HCW treatment conditions (temperature below 180 degrees C and reaction time of 30 min) were adopted, and the amount of water used was only five times that of wood. These conditions were sufficient for the partial removal of hemicellulose and lignin from cell wall supramolecular structure to create nanospace between cellulose microfibrils. This morphological characteristic effectively improved nanofibrillation by disk milling. The fibrillated products with a size of less than 20 nm can be obtained after very short milling time, and this process drastically improved the enzymatic saccharification yield. The energy consumption was much lower than that of other mechanical methods for size reduction to give the same monosaccharide-recovery yield.

Ultra-short contact time conversion of chloromethane to olefins over pre-coked SAPO-34: direct insight into the primary conversion with coke deposition.

Hydrocarbon species trapped in the catalyst that work as the reaction center and govern the conversion and product selectivity of chloromethane transformation were revealed by a very efficient home-made ultra-short contact time pulse reaction system over pre-coked SAPO-34.