Partition of alkaline protease in aqueous two-phase systems of polyethylene glycol 1000 and potassium phosphate

This article presents a study of polyethylene glycol 1000 (PEG1000)/potassium phosphate aqueous two-phase systems (ATPSs) forBacillus subtilis NS99 alkaline protease extraction. The objectives were to evaluate effects of system pH (7.5, 8.5,9.5, and 10.5), and NaCl concentration (0,4,7, and 10% (w/w)) on ATPS binodal curves, effects of system pH, NaCl concentration, and tie-line length (TLL) on alkaline protease partition coefficient (K) and yield (Y%) at room temperature (30±2 ‡C). Casein hydrolysis was used for determination of alkaline protease activity. It was revealed that system pH had the slightest effect on locations of binodal curves (except at pH 10.5). In contrast, addition of NaCl appeared to have a significant effect on phase characteristics since binodal curves of systems with NaCl (4-10% (w/w)) shifted significantly towards the origin in comparison to the ones without NaCl. Increased NaCl concentration from 4 to 10% (w/w), however, showed trivial influence on locations of the binodal curves. Changes of system compositions due to variation in system pH, TLL, and NaCl concentrations obviously resulted in varied obtainable K and Y% of alkaline proteases. Longer TLL and higher pH generally resulted in higher K. In contrast, the lower NaCl concentration, the higher K. Since the same phase volume ration (1:1) was used throughout the experiments, Y% depended solely on K. The most suitable PEG1000/potassium phosphate ATPS was determined at pH 9.5, and comprised PEG1000, potassium phosphate, and NaCl 18.0,13.0, and 0% (w/w), respectively. This system resulted in considerably high K, and Y% of 20.0, and 95.1%, respectively. Information from this study will be important for further development of an ATPS extraction unit for alkaline protease recovery.     

Measurement of hysteresis in crystallization with a quartz crystal sensor

Monitoring of the cycle of crystal formation and dissolution gives important information for manipulating solute concentration and solution temperature for the preparation of mother solution in crystallization processes. In this study a direct monitoring technique using a quartz crystal sensor is applied to the crystallization of potassium bromide solution, and the monitoring performance is investigated. The experimental results indicate that the monitoring shows the detailed process of crystal formation and dissolution, and there is a hysteresis of 0.98 °C between the initiation temperature of crystal formation and the completion temperature of dissolution in the first measurement. In addition, it is demonstrated that the application of the technique is simple and efficient for the control of crystallization processes.     

Temperature and concentration dependent effect of partial glycerides on milk fat crystallization

Two diglycerides (distearin and diolein) and two monoglycerides (monostearin and monoolein) were added to milk fat in a concentration of 0.5% and 1%. The isothermal crystallization behavior was evaluated at 22 °C, 23.5 °C, 25 °C and 26.5 °C by DSC and pNMR. The crystallization kinetic was quantified by means of two models. It was noticed that the effect of the minor components on the crystallization behavior depends on temperature and concentration. The type of esterified fatty acids and the polar head of the amphiphilic molecule determine to what extent partial glycerides influence the nucleation and crystal growth of triglycerides. Moreover the degree of insolubility of partial glycerides in the melt determines which effect (on growth or on nucleation) predominates. Stearic acid based partial glycerides enhance nucleation at low temperatures, while at higher temperatures an interaction with the crystal growth predominates. Oleic acid based partial glycerides have an effect on the nucleation process while no interaction with the crystal growth was observed.     

CRYSTALLIZATION KINETICS AND PRODUCT PURITY OF α-GLUTAMIC ACID CRYSTAL

A continuous mixed-suspension mixed-product removal lpar;CMSMPR) crystallizer was used to study the crystallization kinetics and product purity of glutamic acid crystal in pure solution and impure solution with L-phenylanaline as the impurity. Under the assumption that the crystal growth rate was a function of crystal size, the population balance equation was solved to give the crystal growth and nucleation rates by use of the steady-state population density data. The crystal growth and nucleation rates were suppressed by the presence of impurity. The impurity contents in the crystal products, which were analyzed by a HPLC pre-column method, were found to be related to crystal size, supersaturation, and impurity concentration of solution     

Extraction,purification and application of thermostable and halostable alkaline protease from Bacillus alveayuensis CAS 5 using marine wastes

A marine bacterium Bacillus alveayuensis CAS 5 produced protease when grown at 55 °C for 60 h in 100 ml of basal medium containing 1% SSP (w/v) and purified to 7.77 fold with specific activity of 518.78 U/mg. The optimum temperature, pH and NaCl for enzyme activity were 50 °C, 9 and 35% respectively. The enzyme was highly stable even at 80 °C, pH 12, 35% NaCl and presence of ionic, non-ionic and commercial detergents. The protease was investigated for its application as cleansing additive in blood stain removal. The preset study emphasized that marine wastes can be utilized to generate high value-added products and hidden potential in the production of functional foods.     

结晶法提纯工业磷酸的数学模型与实验研究

为了制备电子级磷酸,采用了悬浮结晶法对工业磷酸进行提纯。分析了结晶法提纯工业磷酸的原理,并基于结晶过程中杂质的有效分配系数对多次结晶后杂质的分布建立了晶体纯度预测模型,同时考察了酸浓度、结晶次数和磷酸原料杂质初始含量对磷酸提纯效果的影响。研究结果表明,采用结晶法提纯磷酸具有良好的效果,能有效地脱除所考察的五种杂质(Li、Mg、Al、Cr、Mn);以一次晶体为原料,在磷酸浓度为84%的条件下,经过3次结晶,和在磷酸浓度为88%的条件下,经过4次结晶,均可以达到美国典型半导体磷酸要求。所建立的晶体纯度预测模型能很好地预测杂质浓度随结晶次数的变化。     

透辉石玻璃陶瓷的制备及其析晶特性研究

以废玻璃粉为原料,采用反应析晶烧结法制备了透辉石玻璃陶瓷。采用差热分析、X射线衍射分析、扫描电镜、能谱、高分辨透射电镜等方法研究了顽辉石-堇青石粉和废玻璃粉混合样品等温烧结过程中顽辉石-堇青石向透辉石转变的演变过程。结果表明:顽辉石-堇青石与玻璃粉在815°C下即可发生反应析晶;900°C保温2 h可获得透辉石为主晶相的玻璃陶瓷。在保温过程中,顽辉石的Mg~(2+)和O~(2-)向玻璃中扩散,玻璃中的Si~(4+)和Ca~(2+)向顽辉石中移动,使顽辉石晶体在b轴方向交替排列的两条链沿c轴方向断开,转变成单链,由Mg~(2+)和Ca~(2+)连接生成透辉石。保温0 h时,由于堇青石[MgO_6]八面体膨胀较小,玻璃中的Si~(4+)、Ca~(2+)、Na~+向堇青石中移动,反应析晶生成钠长石与透辉石;当保温时间延长至2 h时,堇青石[MgO_6]八面体骨架进一步扭曲,生成主晶相为透辉石的玻璃陶瓷。     

Retardation of Crystallization through the Addition of Dairy Phospholipids

The objective of this work was to identify the effects that milk phospholipids (PL) have on crystallization of anhydrous milk fat (AMF). Three mixtures were prepared by adding 0%, 0.01%, and 0.1% PL to AMF. Each mixture was crystallized for 90 min at 24, 26, and 28 °C. The solid fat content was measured as a function of time and fitted to the Avrami equation. Melting point, thermal behavior, viscoelastic properties, and crystal morphology were all measured at 90 min. All assays were repeated, as well as hardness, after being stored at 5 °C for 48 hours. Samples containing PL showed slower crystallization as concentration increased especially at higher temperatures (26 and 28 °C). The addition of PL caused a difference in crystal morphology resulting in visibly larger crystals at 90 min. The elasticity and hardness at 90 min were influenced by the addition of PL at 24 °C with lower values obtained in samples with PL compared to the AMF alone. No differences in hardness nor in elasticity was observed for samples crystallized at 26 and 28 °C. A decrease in melting enthalpy was observed in samples with PL indicating a reduction in crystallization at all temperatures, which was supported by crystal morphology.     

Organogelation Capacity of Epicuticular and Cuticular Waxes from Flax and Wheat Straws

Valorization of the agri-food industry by-products could contribute to curb issues related to food security and environmental problems. Flax and wheat seeds are major products of this industry, but their production is associated with tons of straws that can be valorized for their cuticular and epicuticular waxes. We aimed to determine the organogelation capacity of epicuticular waxes in comparison to cuticular waxes from both flax and wheat straws. Epicuticular waxes from flax and wheat straws have structured canola oil at 2% and 4% (w/w), respectively, whereas cuticular waxes from flax and wheat straws required critical concentrations of 4% and 5% (w/w), respectively. Characterization of the organogelation capacity (onset of crystallization temperature, temperature of phase transition, crystal morphology, solid fat, crystalline structure, and oil binding capacity) was also carried out. The high onset of crystallization temperature (38.1 ± 1.2°C), the phase transition at high temperature (38 ± 1.5°C), and capacity to structure canola oil at low concentration showed that epicuticular wax from flax straw is a promisor fat substitute, presenting organogelation properties comparable to the best results obtained in the literature for other vegetal waxes.     

CRYSTALLIZATION KINETICS OF 2-CHLORO-4,6-DINITRORESORCINOL BY BATCH COOLING CRYSTALLIZATION METHOD

Crystallization kinetics of 2-chloro-4,6-dinitroresorcinol in ethanol was studied by the method of intermittent dynamic analysis. The nucleation rate and crystal growth rate of 2-chloro-4,6-dinitroresorcinol under different crystallization temperatures and stirring rates were estimated. The results show that with an increase of crystallization temperature, both the nucleation rate and crystal growth rate increase. It is further found that when the stirring rate increases, the nucleation rate increases and the crystal growth rate decreases. The technological conditions of cooling crystallization of 2-chloro-4,6-dinitroresorcinol were studied. It is found that when the stirring rate is 180 rpm and the solution is cooled slowly to ? 8°C, the particle size of the products is even and the highest yield of 2-chloro-4,6-dinitroresorcinol is 40.6%.     

Effect of Milk Fat Concentration on Fat Crystallization of Palm Oil-Based Shortenings

The effect of different dosages of anhydrous milk fat (AMF) (25%, 50% and 75%, w/w) on shear-crystallization of fat blends made of refined palm oil, refined palm stearin, and rapeseed oil was studied. Classical techniques as differential scanning calorimetry (DSC), pulsed field gradient nuclear magnetic resonance (pfg-NMR), rheometer, and X-ray diffraction (XRD) were applied to evaluate the crystallization kinetics of fat blends as well as the fat compatibility between components in rapid cooling (15 °C min⁻¹), isothermal crystallization (at 15 °C), and storage (5 °C). Obtained results revealed that the mixtures of palm oils and milk fat had a low compatibility. The co-crystallization between triacylglycerols (TAG) of milk fat and of palm oil occurred during isothermal crystallization and storage resulting in slower crystallization kinetics and the formation of some eutectic mixtures.     

Cell-culture compatible silk fibroin scaffolds concomitantly patterned by freezing conditions and salt concentration

The morphology of freeze-dried silk fibroin 3D-scaffolds was modified by varying both the NaCl concentration and the freezing temperature of the silk fibroin solution prior to lyophilization. Scanning electron micrographs showed that slow freezing at −22 °C generated sponge-like interconnected porous networks, whereas fast freezing at −73 °C formed stacked leaflet structures. The presence of millimolar NaCl (50–250 mM) increased the porosity of the scaffolds and generated small outgrowths at their surface, depending on the freezing regime. Our results suggest that the morphological differences seen between the materials likely depend on ice and NaCl hydrate crystal nucleation and growth mechanisms. Infrared spectroscopy and X-ray diffraction analyses revealed that the salt concentration and freezing conditions induced no structural changes in fibroin. The seeding of P19 embryonic carcinoma cells showed that the presence of salt and freezing conditions influenced the cell distribution into the scaffolds, with salt addition increasing the access of cells to deeper regions.     

Osmotic dehydration of lemon (Citrus limon L.) slices: Modeling mass transfer kinetics correlated with dry matter holding capacity and juice sac losses

Osmotic dehydration of lemon slices was performed using hypertonic NaCl solution. Due to low dry matter holding capacity (DHC) of lemon, the moisture loss, salt gain, and solid loss kinetics during osmotic dehydration were studied by considering the loss of juice sacs from lemon. The slices were immersed in the osmotic solutions maintained with four concentrations of NaCl (5–20%, w/v) and three temperatures (30, 40, and 50°C) for predetermined time intervals (10–180?min). The sample to solution ratio was maintained at 1:10. Azuara model based on Peleg model was used to determine the equilibrium moisture loss and salt gain. Apart from the moisture loss and salt gain, it was found that the loss of solid constituents and juice sacs from the fruit into the osmotic solution was significant. Therefore, the DHC was determined to correlate the rate of solid loss. The DHC was found to be greatly affected by temperature as lemon was less capable to withhold its cell integrity at higher temperature. A combined correlation model was used to determine the effect of osmosis time, solution concentration, and temperature on moisture loss, salt gain, and solid loss. High temperature is not preferable for osmotic dehydration of lemon as it increases losses. The optimal condition was found to be 20% salt concentration and 30°C osmotic solution for 180?min to attain high moisture loss, less solid loss, and required salt uptake within allowable limits.     

Extraction of microbial transglutaminase from <Emphasis Type="Italic">Amycolatopsis</Emphasis> sp. fermentation broth using aqueous two-phase system

Partitioning of microbial transglutaminase (MTG) from Amycolatopsis sp. in the polyethylene glycol (PEG)/salt-based ATPS was investigated for the first time. The key parameters such as the molecular weight of PEG (PEG 600-6000), the type and concentration of phase-forming salt (ammonium sulfate or phosphates), the pH of system (pH 5.0-8.5), and the concentration of neutral salt (0-6% NaCl, w/w) were determined. The partition coefficient of the enzyme was not linear with PEG molecular weight; PEG1000 gave better yield than others. The concentration of PEG1000, ammonium sulfate and NaCl, and the system pH showed effects with different extents on specific activity (SA) and yield of the enzyme. In the ATPS of 26% w/w PEG 1000 and 19% w/w ammonium sulfate in the presence of 5% w/w NaCl and at pH 6.0, MTG was partitioned into the PEG-rich phase with a maximum yield of 86.51% and SA was increased to 0.83. The results of SDS-PAGE showed the MTG produced by the test strain differed from the enzymes reported before. Thus, this study proves that ATPS can be used as a preliminary step for partial purification of MTG from Amycolatopsis sp. fermentation broth.     

Turbidimetry for crystalline fractionation of lard

Development of specific properties of lard, a well-known edible animal by-product and one which plays an important role in Chinese-style foods, was studied by means of multiple-step crystalline fractionation. A method for monitoring the crystallization temperature and crystallization time of lard by spectral turbidity was also studied. The capabilities of the proposed method were experimentally demonstrated through recovery of the fat crystal mass. Six significant changes in turbidity spectra, which correspond to the formation of fat crystals, were observed at various temperatures while cooling the melted lard from 50°C to the final vessel temperature at a constant cooling (0.5°C/min) and agitator rate (50 rpm). Crystallization time for each lard fraction was determined while the peak in turbidity was observed in the process of cooling at a specific temperature. Determination of crystallization time by means of turbidimetry correlated with the increase in deposition of fat crystals. No significant increase in fat crystal mass was observed when cooling prolongation after the turbidity peak for the sample was measured. Attributes of lard fractions were characterized by iodine value, saponification value, fatty acid composition, and melting profile of crystallization temperature. Based on the results, turbidimetry might be suggested as a fast and inexpensive method for monitoring the crystallization temperature and crystallization time for the routine crystalline fractionation process.     

Sonocrystallization of Interesterified Soybean Oil With and Without Agitation

Interesterified soybean oil was crystallized at 29, 34, and 35 °C with and without the use of high‐intensity ultrasound. Samples were crystallized using either (1) continued agitation for the entire crystallization process (CA) or (2) agitation for 10 min (A10) followed by static crystallization. Sonication and agitation decreased the induction period of nucleation at higher temperatures and changed the crystal morphology, crystallization kinetics, and viscoelasticity of the sample. Sonication reduced the crystal sizes and significantly (P <0.05) increased the viscosity (5.2 ± 1.2 to 2369.6 ± 712.1 Pa s) and elastic modulus (83.2 ± 4.1 to 69,236.7 ± 26,765 Pa) of the crystalline networks obtained at 29 °C under A10 condition. An increase in viscosity and elasticity was also observed for sonicated samples crystallized at 34 and 35 °C under A10 and all CA conditions but these differences were not statistically significant (P >0.05). Sonication increased crystallization rates for all conditions tested. Kinetic constants obtained from an Avrami fit increased from1.3 × 10^?5 to 6.8 × 10^?5 min^?n for samples crystallized at 29 °C A10 without and with sonication, respectively, and from 2.6 × 10^?9 to 2.4 × 10^?7 min^?n for samples crystallized at 34 °C A10 without and with sonication, respectively. This increase in the crystallization rate was also observed for samples crystallized under the CA condition at 29 °C.     

D-核糖结晶工艺探讨

结晶过程的原则是争取最大的结晶速度，尽可能提高成品收率，保证晶粒的均匀整齐。而影响结晶的因素有：溶液浓度、晶种质量、晶体生长速率、过饱和度的大小、结晶温度、溶液pH值、溶液杂质等。本文探讨了D-核糖结晶过程中溶液浓度、溶媒（乙醇）含量和降温方式等工艺的优化。     

Crystallization behavior of CMAS and NaVO3+CMAS mixture and its potential effect to thermal barrier coatings corrosion

Calcium-magnesium-alumina-silicate (CMAS) and molten salt corrosion pose great threats to thermal barrier coatings (TBCs), and recently, a coupling effect of CMAS and molten salt has been found to cause even severer corrosion to TBCs. In this study, the crystallization behavior of CMAS and CMAS+NaVO₃ is investigated for potentially clarifying their corrosion mechanisms to TBCs. Results indicated that at 1000 °C and 1100 °C, CMAS was crystallized to form CaMgSi₂O₆, while at 1200 °C, the crystallization products were CaMgSi₂O₆, CaSiO₃ and CaAl₂Si₂O₈. The introduction of NaVO₃ in CMAS reduced the crystallization ability, and as the NaVO₃ content increased, glass crystallization occurred at a lower temperature, with crystallization products mainly consisting of CaAl₂Si₂O₈ and CaMgSi₂O₆. At 1200 °C, CMAS+10 wt% NaVO₃ was in a molten state without any crystallization, which suggested that NaVO₃ addition in CMAS could reduce its melting point, indicating enhanced penetration ability in TBCs and thus increased corrosiveness.     

Effects of Sorbitan Monostearate and Monooleate on the Crystallization and Consistency Behaviors of Cocoa Butter

The crystallization behavior of cocoa butter (CB) is the essential structuration issue in the development of chocolate products. An alternative to modify and control the crystallization patterns of CB in chocolate production is the incorporation of specific emulsifiers in their formulations. In this work, the effects of sorbitan monostearate (SMS) and sorbitan monooleate (SMO) in the crystallization and consistency behaviors as well as on the microstructure of CB were evaluated. CB samples at three different concentrations (0.5, 1.0 and 1.5 % w/w) of SMS and SMO were prepared and their main physical–chemical attributes determined. CB added with 1.5 % of SMS showed the largest effects with a sharp increase in the onset of the crystallization temperature (from 19.3 to 23.8 °C) and doubling the yield value (consistency) of pure cocoa butter. The classic two-step isothermal crystallization behavior and morphology of CB were also modified with the addition of SMS. A possible explanation based on the solubility of SMS in an organic medium and its ability of self-assembling was suggested as a mechanism for SMS performance in CB. SMS was considered as a potential crystal modifier for CB by changing its crystal structure and enhancing its thermal resistance—factors that favor the use of this emulsifier in the production of improved thermally stable chocolates.     

Rapid Crystallization of Silicalite Nanocrystals in a Capillary Microreactor

Silicalite nanocrystals were synthesized in a pressurized capillary microreactor at 150 °C within 11 min with synthesis solutions aged at 80 or 100 °C for 1–6 h. The effects of aging of the synthesis solution and the reaction pressure were examined. The resulting products were characterized by XRD, DLS, TEM, FT‐IR and TG‐DSC. Aging of the synthesis solution played an important role in shortening the crystallization time of the silicalites. The synthesis pressure should be higher than the saturation vapor pressure of water at 150 °C (～0.5 MPa) and silicalite nanocrystals with crystallinities of 70 % and 100 % could be produced from the synthesis solution aged at 100 °C for 2 h with residence times of 11 min at 0.7 MPa and 1 MPa, respectively. The mean particle sizes of these two samples were 102.2 nm and 166.4 nm, respectively. Thus, the crystallization time of the silicalite nanocrystals is shown to be significantly reduced in the capillary microreactor compared to a traditional batch system.