Green biosynthesis of rare DHA-phospholipids by lipase-catalyzed transesterification with edible algal oil in solvent-free system and catalytic mechanism study.

Docosahexaenoic acid (DHA)-enriched phosphatidylcholine (PC) has received significant scientific attention due to the health benefits in food and pharmaceutical products. In this work, the edible algal oil rich in DHA-triacylglycerol (DHA-TAG) without pretreatment was first used as the DHA donor for the transesterification of phospholipids (PLs) to prepare three kinds of rare PLs, including DHA-PC, DHA-phosphatidylethanolamine (DHA-PE), and DHA-phosphatidylserine (DHA-PS). Here, 153 protein structures of triacylglycerol lipase (EC 3.1.1.3) were virtually screened and evaluated by transesterification. PLA1 was the best candidate due to a higher DHA incorporation. Results showed that the transesterification of PC with DHA-TAG at 45°C and 0.7% water content (without additional water addition) could produce DHA-PC with 39.1% DHA incorporation at 30 min. The different DHA donors, including forms of fatty acid, methyl ester, and triglycerides, were compared. Molecular dynamics (MD) was used to illustrate the catalytic mechanism at the molecular level containing the diffusions of substrates, the structure-activity relationship of PLA1, and the effect of water content.

Synthesis and characterization of magnetic organic montmorillonite: efficient adsorption of hexavalent chromium.

This research compared two potential adsorbents for the efficient adsorption of toxic hexavalent chromium. The non-magnetic material STAC-Mt and the magnetic material FeSO4-STAC-Mt were synthesized by a simple impregnation method using montmorillonite (Mt), octadearyl dimethyl ammonium chloride (STAC) and ferrous sulfate as raw materials. The structural and morphological characteristics of both adsorbents were investigated by BET, XRD, FTIR, Zeta, VSM, TEM, SEM and XPS techniques. SEM and TEM results clearly revealed that FeSO4-STAC-Mt had a more loosely curled structure than STAC-Mt and the existence of well dispersed diamond-shaped magnetic particles. The saturation magnetization intensity of 17.949 emu/g obtained by VSM further confirmed the presence of magnetite particles in FeSO4-STAC-Mt. Due to the superparamagnetic properties of magnetite, the adsorption performance of FeSO4-STAC-Mt was better than STAC-Mt. FeSO4-STAC-Mt adsorbed up to 43.98 mg/g of Cr(VI), meanwhile it was easily separated from the reaction mixture by an external magnetic field. Intermittent adsorption studies at pH, adsorbent dosage and time revealed a rapid Cr(VI) adsorption process. In combination with response surface optimization analysis, a removal rate of 98.03% of Cr(VI) was obtained at pH 5-6. The adsorption process was properly described by the pseudo-second-order kinetic equation and the Langmuir equation, and the adsorption process was chemisorption and single molecular layer adsorption. In addition, the removal of Cr(VI) reached 72.68% after five cycles, demonstrating the good stability of the FeSO4-STAC-Mt.

The efficient and green synthesis of biodiesel from crude oil without degumming catalyzed by sodium carbonate supported MoS2.

The transesterification of lecithin with methanol catalyzed by 23 kinds of alkaline salts was investigated for the preparation of biodiesel. Sodium carbonate was confirmed as the best catalyst due to its excellent catalytic performance, environmental friendliness, and great stability. Next, it was successfully immobilized on the surface of hierarchical nanosheets of MoS2. The prepared catalyst was characterized via XRD, FTIR, SEM, and TEM techniques. After immobilization, the highest specific activity reached 40.58 ± 0.78 U mgNa2CO3 -1, which was 2.43 times higher than that of unsupported Na2CO3. Meanwhile, the highest yield reached 99.8%. The excellent performance of the supported catalysts was attributed to a synergistic effect between MoS2 and the absorbed sodium carbonate. Firstly, sodium carbonate was uniformly dispersed on the surface of MoS2 to minimize the mass transfer resistance. Secondly, the electron-rich outer layer of MoS2 promoted the deprotonation of methanol to form methoxy anions. The prepared catalyst was further applied in the transesterification of lecithin-containing triglycerides to prepare fatty acid methyl esters (FAMEs). The experimental results showed that the addition of lecithin would promote the transesterification of triglycerides. The yields of FAMEs were close to 100% in all cases when the lecithin content was increased from 1% to 40%. Hence, this supported sodium carbonate catalyst should be a promising candidate for biodiesel production from crude oil without degumming.

Catalytic wet peroxide oxidation degradation of magenta wastewater and preparation of FeOCl/montmorillonite.

The iron oxychloride/pillared montmorillonite (FeOCl/MMT) catalyst was prepared by wet impregnation method and solid melting method. Various characterization techniques were used to analyze the microscopic morphology and structure of a series of catalysts. Moreover, the catalysts were used to treat magenta-simulated dye wastewater through catalytic wet peroxide oxidation (CWPO) degradation. The magenta removal rate and chemical oxygen demand (COD) removal rate of the magenta-simulated dye wastewater were used to evaluate the catalytic performance of the catalyst, and the optimal catalyst preparation conditions were selected. The results showed that the solid melting method was more favorable to the preparation of the catalyst, and the COD removal rate of wastewater can reach 70.8% when the FeOCl load was 3%. Moreover, 96.2% of the magenta in the solution was removed. The COD removal rate of the magenta wastewater decreased by only 12.4% after the catalyst was repeatedly used six times, indicating that the catalyst has good activity and stability. The Fermi equation can simulate the reaction process of the catalyst treating magenta wastewater at high temperature.

Choline derivatives immobilized on silica to catalyze transesterification reaction for production of glycerophosphocholine.

Choline derivatives were covalently immobilized on the surface of γ -aminated silica. The obtained immobilized choline derivative was then successfully used for a transesterification reaction to produce glycerophosphocholine (GPC). Fourier transform infrared analysis and thermogravimetric analysis/differential thermal gravimetry indicated that the surface of the γ -aminated silica was covered by choline derivatives and the highest immobilization amount reached 1.1 mmol/g under optimal conditions. More importantly, the highest yield of GPC reached 97.9% during transesterification. With regard to GPC in food or medicine for human use, the immobilization technology can avoid catalyst contamination of the product and increase the safety of the product. The recyclability and stability of the immobilized choline derivative were excellent, as demonstrated by its use 20 times without any loss of productivity. A first-order kinetic model was employed and the relevant parameters were calculated to investigate kinetic characteristics of transesterification.

Two-step modification of silica for efficient adsorption of phosphatidylcholine in water and application in phospholipase D-catalyzed transphosphatidylation.

An efficient and green aqueous-solid system was introduced for phospholipase D-mediated transphosphatidylation. γ-(2,3-epoxypropoxy) propytrimethoxysilane was covalently bound to silica and esterified by acetic acid, which acted as an anchor molecule to facilitate the adsorption of phosphatidylcholine (PC) in aqueous solutions. Obtained silica-adsorbed PC was successfully used for transphosphatidylation to produce phosphatidylserine (PS). The PC loading and PS yield reached 98.8 and 98.3%, respectively. A new model was proposed to illustrate the adsorption and enzymatic processes. Moreover, this aqueous-solid system provides a promising way for the continuous production. Four kinds of phospholipids were biosynthesized in the pack-bed reactor. The stability of the aqueous-solid system was excellent, as demonstrated by its use 30 times without any loss of the productivity. The product was eluted by coconut oil and manufactured into microcapsules. Toxic agents were completely avoided in the whole production process.

A comparison between continuous and batch processes to produce phosphatidylserine in the efficient and green aqueous-solid system.

The efficient and environmentally friendly aqueous-solid systems employed Triton-X-100-modified silica as the "artificial interface" to adsorb phosphatidylcholine (PC) in purely aqueous solutions and silica-adsorbed PC was successfully used for phospholipase D (PLD)-mediated transphosphatidylation. Three kinds of silicas with different sizes were employed to investigate advantages and disadvantages of batch and continuous technologies for PLD-catalyzed transphosphatidylation in aqueous-solid systems. The highest yields of product were obtained in the batch technology, but the continuous production had the simplest operational process and highest space-time yield. After transphosphatidylation, the product adsorbed on carriers were eluted by coconut oil and used to manufacture relevant hard, soft, and micro-capsules. Special attention has been paid to the preparation of microcapsules. Toxic solvents were completely avoided in the whole technological process including production and product packaging. © 2019 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2777, 2019.

Efficient and green aqueous-solid system for transphosphatidylation to produce phosphatidylhydroxybutyrate: Potential drugs for central nervous system's diseases.

The synthesis of nonnatural phospholipid, phosphatidylhydroxybutyrate (PB), was firstly introduced by phospholipase D (PLD)-mediated transphosphatidylation of phosphatidylcholine (PC) with sodium γ-hydroxybutyrate (NaGHB) in the aqueous-solid system. Nanoscale silicon dioxide (NSD) was employed as a carrier to provide an "artificial interphase" between PC and PLD. Special attention has been paid to the effect of the PC coverage on the surface area of hybrids of NSD-PC, the PC loading and the yield of PB. Results indicated that the highest PC loading of 98.3% and the highest PB yield of 97.3% were achieved. In addition, the free PLD in the aqueous-solid system showed the greater stability and pH tolerance than that in the traditional liquid-liquid system. The operational stability of free PLD solution was investigated. The yield of PB remained 70.7% after being used for five batches. The authors provide a new idea for drug design and the potential source of PB for medical experiments. PB is a potential drug and may have the excellent performance in the treatment of central nervous system's diseases. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2726, 2019.

Improving phospholipase D activity and selectivity by bio-imprinting-immobilization to produce phosphatidylglycerol.

Phospholipase D (PLD) was firstly hyperactivated by the bio-imprinting and, then, these hyperactivated PLD molecules were immobilized by adsorption and precipitation, followed by cross-linking. The high degree of conformational rigidification provided by intra- and intermolecular cross-linking can make PLD "remember" imprint-induced characteristics even in aqueous solutions. The obtained immobilized PLD showed the excellent catalytic performance. The maximum activity of immobilized PLD reached 166953 U/gprotein, which was approximately 14 times higher than that of free form (11922 U/gprotein). Moreover, the selectivity of PLD was significantly enhanced after immobilization. The yield of PG and PA reached 94.0% and 5.96%, respectively. Compared with the serious hydrolysis in the free PLD (35.3% yield of PA), the side reaction was minimized in this work. This may be the first description of the remarkably high improvement of the activity and selectivity of PLD through the immobilization technology.

A Facile Strategy to Prepare Zr4+-Modified Bi2WO6 with Enhanced Visible-Light Photocatalytic Activities.

A series of Zr4+-modified Bi2WO6 photocatalysts were synthesized using a hydrothermal method employing Bi(NO3)3·5H2O, Na2WO4·2H2O and Zr(NO3)4 as precursors. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), UV-vis absorption spectroscopy (UV-vis) and photoluminescence spectroscopy (PL). The investigations indicated that the flower-like Bi2WO6 3D structures were constructed from a large number of 2D layers of interconnected nanoplates. The energy gaps of Zr4+-modified Bi2WO6 decreased compared with that of pure Bi2WO6. In addition, fluorescence quenching was observed because the recombination of charge carriers was effectively suppressed by Zr4+. The photocatalytic properties of samples were evaluated by the degradation of Rhodamine B (RhB) solution under visible-light irradiation. The results indicate that the 1.0 mol% Zr4+-modified Bi2WO6 possesses obviously enhanced photocatalytic activity, showing the great potential for wastewater purification. In addition, a tentative photocatalytic mechanism is proposed to understand the experimental results over the Zr4+-modified Bi2WO6 photocatalysts.

High-Yield and Sustainable Production of Phosphatidylserine in Purely Aqueous Solutions via Adsorption of Phosphatidylcholine on Triton-X-100-Modified Silica.

Triton X-100 was covalently bound to a surface of silica and acted as an anchor molecule to facilitate the adsorption of phosphatidylcholine (PC) in a purely aqueous solution. The silica-adsorbed PC obtained was successfully used for phospholipase D (PLD)-mediated transphosphatidylation in the production of phosphatidylserine (PS). Organic solvents were completely avoided in the whole production process. The PC loading and PS yield reached 98.9 and 99.0%, respectively. Two adsorption models were studied, and the relevant parameters were calculated to help us understand the adsorption and reaction processes deeply. In addition, the silica-adsorbed PC provides a promising way to continuously biosynthesize PS. A packed-bed reactor was employed to demonstrate the process flow of the continuous production of PS. The recyclability and stability of the Triton-X-100-modified silica were excellent, as demonstrated by its use 30 times during continuous operation without any loss of the productivity.

Aqueous-Solid System for Highly Efficient and Environmentally Friendly Transphosphatidylation Catalyzed by Phospholipase D To Produce Phosphatidylserine.

The purely aqueous system of phospholipase D (PLD)-mediated transphosphatidylation using pre-existing carriers for the adsorption of phosphatidylcholine (PC) to act as an "artificial interface" was introduced to replace the liquid-liquid system. Toxic organic solvents are avoided during the reaction, and the free enzyme can be simply reused by centrifugation. Special attention has been paid to the effect of the pore diameter and surface area of silica gel 60H covered with PC molecules on the yield of phosphatidylserine (PS). Results indicated that the highest PS yield of 99.5% was achieved. Moreover, 73.6% of the yield of PS was obtained after being used for six batches. This is the first description of the remarkably high reusability of free enzymes for enzymatic synthesis of PS as well. The excellent results make the aqueous-solid system more promising candidates for the industrial production of PS.

Degradation of 4-nitrophenol (4-NP) using Fe-TiO2 as a heterogeneous photo-Fenton catalyst.

Photocatalytic degradation of 4-nitrophenol was investigated using Fe-doped (1, 3, 5 and 8 wt.% Fe) TiO(2) catalysts under UV light irradiation in aqueous dispersions in the presence of H(2)O(2). Photocatalysts with the lowest Fe content (1%) showed a considerably better behavior with respect to the unloaded TiO(2) and the catalysts with higher Fe contents. Photocatalytic degradation was studied under different conditions such as amounts of 1% Fe-TiO(2) catalyst, H(2)O(2) dose and initial pH of 4-NP solution. The results indicated that about 67.53% total organic carbon of a solution containing 20 mg L(-1) 4-NP was removed at pH 6.17 by using 4.9 mM of H(2)O(2) and 0.4 g L(-1) of the catalyst in a 2-L batch photo-reactor, the complete degradation of 4-NP occurring after 60 min. It was also observed that catalytic behavior could be reproduced in consecutive experiments without a considerable decrease of the UV/Fe-TiO(2)/H(2)O(2) process efficiency.