To develop appropriate biocompatible nucleants, glutathione (GSH), glycine (Gly) and cysteine (Cys) were used as the biomolecular additives to study their effect on the regulation of lysozyme crystallization. Characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, circular dichroism, etc., the results show that GSH can effectively promote protein crystallization under even lower concentrations of lysozyme by enhancing the nucleation rate, comparing with the additives of Gly and Cys, whereas lysozyme crystal structures produced in the presence of the biomolecular additives are similar to those in the absence of the additives. It shows in combination with molecular modeling that the stronger interactions between small biomolecular additives and the lysozyme LOOP accelerate the heterogeneous nucleation. It is suggested that such small biomolecules can be used as promising nucleants for promoting protein crystallization in the food and pharmaceutical industries.
In this study, we investigated the synergistic effect of a zwitterionic surfactant (cocamidopropyl betaine) and amino acid surfactant (sodium lauroyl sarcosinate) by measurements of surface tension, rheological properties, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The results confirm the formation of wormlike micelles in the mixed system, which leads to superior surface activity as compared to that of an individual surfactant. Stable and dynamic viscoelastic measurements were also performed to explore the characteristics of wormlike micelles at different mole fractions, pH values, and temperatures. The results indicate that the strongest wormlike structure formed under the conditions of X 1 = 0.5, pH = 4.7, and C T = 600 mmol/L. The size and morphology of the mixed micelles were obtained by DLS and TEM. The results of this work offer insight into the interaction between zwitterionic and amino acid surfactants, which will contribute to the design of complex surfactants.
Geraniol is a monoterpenoid alcohol with various applications in food, cosmetics, and healthcare. Corynebacterium glutamicum is a potential platform for terpenoids production because it harbors the methylerythritol phosphate pathway. To engineer C. glutamicum to produce geraniol, two different truncated geraniol synthases (GESs) were respectively expressed, and strain LX02 expressing the truncated GESs from Valeriana officinalis (tVoGES) produced 0.3 mg/L of geraniol. Then, three geranyl diphosphate synthases (GPPSs) were combinatorially co-expressed with tVoGES to improve geraniol production. The amounts of produced geraniol were all higher than that produced by strain LX02. Strain LX03 co-expressing ERG20F96W–N127W (ERG20WW) and tVoGES produced the highest amount, 5.4 mg/L. Subsequently, the co-overexpression of 1-deoxy-d-xylulose-5-phosphate synthase (dxs) and isopentenyl diphosphate isomerase (idi) further increased the production to 12.2 mg/L in strain LX03. Lastly, the production of geraniol was increased to 15.2 mg/L via fermentation optimization. To our knowledge, this is the first report on the engineering of C. glutamicum to produce geraniol and thus can serve as a reference for other monoterpenoid production studies.
The dietary fiber in oats is mainly concentrated in the bran; however, the oat bran is mostly used for livestock and poultry feed and thus has a low utilization rate and low added value. In this study, insoluble dietary fiber (IDF) was extracted by a combination of α-amylase and neutral protease. The optimal extraction conditions of the IDF were obtained by response surface methodology. The material-to-water ratio was 1:12.1, the concentration of α-amylase was 1.85%, and the hydrolysis time was 39.14 min. After purifying the crude fiber with 4% sodium oxide (NaOH), 70 °C hot water, and anhydrous ethanol, the purity of dietary fiber exceeded 95%. X-ray diffraction analysis indicated that the IDF was predominantly amorphous. Scanning electron microscopy showed that the IDF surface exhibited a loose porous network structure. Fourier-transform infrared spectroscopy of the crude IDF showed characteristic absorption peaks at 3626, 2929, 1667, 1538, 1455, 1242, and 1048 cm−1, while the infrared spectrum of the purified IDF showed characteristic absorption peaks at 3401, 2924, 1744, 1643, 1418, and 1040 cm−1, which is consistent with the structure of cellulose polysaccharide. Differential scanning calorimetry analysis showed that there were three exothermic peaks at 270–310 °C, 320–350 °C, and 440–460 °C, which may represent the pyrolysis peaks of hemicellulose, cellulose, and lignin, respectively, indicating that the oat bran IDF had good thermal stability. The results indicate that the oat bran IDF can be used for the production of dietary fiber products and health-care products.
In this work, a facile and effective strategy to prepare three-dimensional (3D) hierarchical flower-like Mg–Al layered double hydroxides (3D-LDH) was developed via a one-step double-drop coprecipitation method using γ-Al2O3 particles as a template. The characterization and experimental results showed that the calcined product, 3D-LDO, features a large specific surface area of 204.2 m2/g, abundant active sites, and excellent adsorption performance for Congo red (CR), methyl orange (MO), and methyl blue (MB). The maximum adsorption capacities of 3D-LDO for CR, MO, and MB were 1428.6, 476.2, and 1666.7 mg/g, respectively; such performance is superior to that of most reported adsorbents. The adsorption mechanism of organic anionic dyes by 3D-LDO was extensively investigated and attributed to surface adsorption, the memory effect of 3D-LDO, and the unique 3D hierarchical flower-like structure of the adsorbent. Recycling performance tests revealed that 3D-LDO has satisfactory reusability for the three organic anionic dyes.
A pore-array intensified tube-in-tube microchannel (PA-TMC), which is characterized by high throughput and low pressure drop, was developed as a gas–liquid contactor. The sulfite oxidation method was used to determine the oxygen efficiency (φ) and volumetric mass transfer coefficient (k L a) of PA-TMC, and the mass transfer amount per unit energy (ε) was calculated by using the pressure drop. The effects of structural and operating parameters were investigated systematically, and the two-phase flow behavior was monitored by using a charge-coupled device imaging system. The results indicated that the gas absorption efficiency and mass transfer performance of the PA-TMC were improved with increasing pore number, flow rate, and number of helical coil turns and decreasing pore size, row number, annular size, annular length, and surface tension. The φ, ε and k L a of PA-TMC could reach 31.3%, 1.73 × 10−4 mol/J, and 7.0 s−1, respectively. The Sherwood number was correlated with the investigated parameters to guide the design of PA-TMC in gas absorption and mass transfer processes.