Production of astaxanthin by Phaffia rhodozyma using peat hydrolysates as substrate

Peat hydrolysates prepared with and without acid and under various temperatures were tested in the growth of the yeast Phaffia rhodozyma ATCC 24202, which synthesizes carotenoids, including astaxanthin. The hydrolysate that resulted in the best growth of P. rhodozyma biomass was subsequently used as substrate for the submerged culture of the yeast, and the growth conditions were optimized. Those studied included initial substrate concentration, initial pH, incubation temperature, fermentation time and agitation rate. The optimum growth conditions produced approximately 4.6 g dm^?3 of dry biomass with a crude protein content of 47% (dry weight basis). The mean astaxanthin content of the yeast cultivated under these conditions, 1567 μg g^?1 dry yeast, was also the highest produced in this work, and compares favourably with other results reported in the literature.     

Fumaric acid production from hydrolysates of starch-based substrates

Fumaric acid production by Rhizopus arrhizus from commercial hydrolysates of corn starch (i.e. glucose molasses) was studied at different initial concentrations of glucose (S) and C:N ratios (R) by performing a 3² factorial experiment. By using the response surface methodology and statistical analysis, fumaric acid (Y_F) and mycelial biomass (Y_x) yields, as referred to the initial concentration of glucose and fumaric acid productivity (P_F), were fitted to the only significant first-order effects of S and R with mean percentage errors ranging from 11 to 15%. The resulting empiric models were used to determine the optimal values of S (100–130 g dm^?3) and R (150–210 g-atom C per g-atom N) associated with Y_F and P_F varying in the ranges 40–49% and 7–8.5 g dm^?3 day^?1, respectively. After establishing the validity of these data at the 95% confidence level, an optimal operating condition (S = 120 g dm^?3 and R = 150) was further tested using other substrates (i.e. glucose and acid or enzymatic hydrolysates of cassava, corn and potato flours). Statistically significant improvements in the fumaric acid yield and productivity were determined with respect to the predicted values. Since the highest values of Y_F and P_F were obtained from the acid hydrolysates of the starch-based materials and such values were also found to be insensitive to the substrate used (at a probability level of 0.05), the above operating condition might be further employed to minimise fumaric acid production costs as a function of the feedstock used.     

泥炭腐植酸类物质在洁净煤技术中的应用

介绍了泥炭腐植酸类物质用作水煤浆添加剂和型煤粘结剂的理论基础和实际应用效果。结果表明,将泥炭中含有的大量腐植酸类物质经过改性,用作水煤浆添加剂,在新汶煤、八一煤、邢台煤、兖州煤、鹤岗煤、抚顺煤、神华煤、双鸭山煤等煤种上使用,制浆浓度在65%～69%,粘度在1000mPa·s左右;用作型煤粘结剂,添加量在7%～10%,单个球的冷强度为55～88kg,热强度为50～70kg,常温下耐水性好,对灰分无增加,对环境无污染。     

泥炭土及其富含的腐殖质和腐植酸酸碱性质研究

为了更准确地解释天然有机质与阳离子的结合行为,必须研究两种状态下的天然有机质,即聚合态和溶解态。本研究以泥炭中的腐黑物和腐殖酸为试验材料,在不同离子强度下进行电位滴定试验。其中,腐植酸样品分为溶液(溶解态腐植酸)和悬浮液(聚合态腐植酸)两种处理,将得到的相应电荷变化曲线与之前获得的泥炭滴定曲线采用NICA-唐南模型进行比较分析。结果表明,在整个滴定过程中,溶解态的腐植酸都得到了较好的电荷变化曲线,而同样条件下,聚合态的腐植酸由于在pH<6的条件下,构象发生了变化,样品不断溶解,没能得到确切的电荷变化曲线。与此同时,本研究还发现,泥炭和腐黑物显示出相似的质子结合行为,但都与腐殖酸不同。其中,唐南模型中参数b的值,与滴定标准液的体积和离子强度有关,泥炭和腐黑物受二者影响较大,而无论是溶解态的还是聚合态的腐植酸受影响都较小。另外,泥炭和腐黑物中酚基官能团和羧基官能团比例也比腐殖酸的要大。NICA-唐南模型揭示了泥炭与阳离子结合能力与腐黑物更为相似。     

Mechanism of formation of chloropropanols present in protein hydrolysates

Chloropropanols are formed in protein hydrolysates by the reaction of hydrochloric acid with residual lipids associated with the proteinaceous materials used in their production. The products formed from glycerol, triolein, 1,2-diacyl-sn-glycero-3-phosphorylcholine and soya meal have been analyzed by thin-layer and gas chromatography. The yields and isomer ratios of the chloropropandiols and dichloropropanols formed are interpreted in terms of reaction mechanisms for their formation, which involve preferential nucleophilic substitution by the chloride anion at positions activated by neighboring ester groups. These provide anchimeric assistance and govern regioselectivity through steric and electronic effects.     

乳酸连续化发酵进展

对一些新型的乳酸连续化发酵装置,包括恒浊器、两级恒化器、两级固定床、两级膜细胞循环反应器、三相流化床-电渗析、塑料支持生物膜反应器及相应的发酵条件进行了综述;讨论了连续化发酵的控制(无反馈控制、反馈控制)、数学模型、最优化方法;并分析了不同连续化发酵装置的优缺点及前景.     

Process for production of arachidonic acid concentrate by a strain of mortierella alpina

Various Mortierella alpina fungi were screened for their capacities to produce arachidonic acid. A strain of M. alpina was found to show the highest productivity. Arachidonic acid content of biomass and overall yield per litre of culture was highest in soya flour supplemented medium which produced dispersed mycelium. When the glucose concentration in the medium was varied from 30 to 100 g/L, biomass, lipid, arachidonic acid content of biomass and arachidonic acid yield increased with increasing glucose concentration. Several natural oils, when added to the growth medium, stimulated arachidonic acid production. After fermentation in a 20-L fermenter under optimal culture conditions, the arachidonic acid yield was 5.3 g/L, representing 34.2% w/w of total fatty acids and 13.7% w/w of biomass. An extract containing 72.5% w/w arachidonic acid was prepared from the recovered mycelium.     

Theory of the substrate length in polymer crystallization: Surface roughening as an inhibitor for substrate completion

A model is proposed for the physical origin of the substrate length L that appears in the customary treatment of the regime I→II growth rate transitions which occur in certain polymers during crystallization from the melt. (A previous analysis of growth rate measurements showed that L ≈ 0.77 μm at the I→II transition in polyethylene). L is treated as a ‘persistence length’ between defects that have the capacity to inhibit substrate completion. The defects are pictured as resembling the Greek letter Ω (omega) in their most extended state; in their normal state they are represented as hemispherical or disc-like amorphous patches that are pinned onto the substrate. The omega defect can form on the substrate by drawing in a portion of one of the cilia, loose loops, or interlamellar links that are characteristic of the ‘variable cluster’ representation of the molecular morphology of lamellar semicrystalline polymers. The formulation relates L to the equilibrium free energy of formation of the omega defect, which is viewed as being principally entropic. Thus we derive $\text{L∝(}\text{stem width}\text{) ×}\text{exp}\text{(?}\text{ΔS}\text{R}\text{)}$. From the known value of L for polyethylene, it is determined that the experimental entropy of formation of the defect is ΔS_expt. = ? 12.6±1.5 cal mole^?1 deg^?1. This is justified on basic grounds by first applying nucleation theory to estimate the number of chain units $\text{n}{}_{\mathrm{\Omega }}$ in the defect of critical size. Then from partition functions for once- and twice-pinned polymer chains on a surface, which gives $\text{ΔS = ?fR}\text{ln}\text{n}{}_{\mathrm{\Omega }}$ with f～ 2.0 to 2.5 depending on defect shape, one arrives at a theoretical estimate of ΔS for the omega defect in polyethylene that is in good agreement with the experimental value. This indicates that the omega defect model for L is reasonable on energetic grounds. It is shown further that the model is consistent in a number of respects with what is known about the I→II transition and L. Criteria for the occurrence of I→II transitions are presented, and the range of validity of the theory is discussed. It is noted that the I→II transition may be diffuse or absent in many cases, either because the equilibrium distribution is not attained or because the lifetime of the defects is too short in comparison with the residence time. Thus in many polymers, regime I may be missing so that regime II (with its locally rough growth front) will persist up to quite high temperatures, i.e., up to the practical limit of slow growth.     

Activity of a novel titanium-supported bimetallic PtSn/Ti electrode for electrocatalytic oxidation of formic acid and methanol

Bimetallic platinum–tin nanoparticles were co-deposited on a titanium surface using a simple one step hydrothermal method process. The electrochemical catalytic activity of this titanium-supported nanoPtSn/Ti electrode towards the oxidation of formic acid and methanol in 0.5 M H₂SO₄ was evaluated by voltammetric techniques, chronoamperometric responses and electrochemical impedance spectra (EIS). According to the cyclic voltammograms of the oxidation of both formic acid and methanol, the nanoPtSn/Ti presents high anodic current densities and low onset potentials. Potential-time transient measurements show that the nanoPtSn/Ti exhibits high steady-state current densities for the oxidation of both formic acid and methanol. The EIS data indicate that the nanoPtSn/Ti presents very low electrochemical impedance values, showing that for the oxidation of both formic acid and methanol, low charge transfer resistances are present on the nanoPtSn/Ti catalyst. This confirms the high electrocatalytic activity of the nanoPtSn/Ti for the formic acid and methanol oxidation.     

Validation of a method for gas chromatographic analysis of eicosapentaenoic acid and docosahexaenoic acid as active ingredients in medicinal products

A gas chromatographic method for the determination of all-cis-5,8,11,14,17-eicosapentaenoic acid (EPA) and all-cis-4,7,10,13,16,19-docosahexaenoic acid (DHA) as active ingredients in medicinal products was developed and validated. In accordance with the rules governing medicinal products in the European Community, the method establishes relations between label claims of active ingredients and known reference standards. A routine for examining instrument status is proposed. The relative standard deviation was 1% (n=26) for determination of the empirical response factors of EPA ethyl ester and DHA ethyl ester relative to the internal standard, C23:0 methyl ester. This experiment included two columns and EPA and DHA standards from two different suppliers and was carried out over a five-month period. Repeatability (n=6) for low and medium concentrates of glycerides and high concentrates of ethyl esters, expressed as coefficient of variation, was 4, 0.7 and 0.7%, respectively. Accuracy (n=6) determined as percent recovery was better than 98% for all sample types. Analytical results from a twelve-month stability study of the high concentrate are shown. Presented at the AOCS Annual Meeting in Chicago, IL, May 1991.     

过乙酸氧化法制备环氧环己烷的工艺研究

用过乙酸作氧化剂在二氯甲烷体系中氧化环己烯制得了环氧环己烷。考察了各种影响因素,得到最优工艺条件为:环己烯与过乙酸质量比为1∶1.25,溶剂二氯甲烷用量为环己烯质量的2倍,保持反应体系pH为5.8,反应温度为25℃,滴加反应时间和保温反应时间都为1.5 h。经精馏处理后,产品收率达到79.0%,产品纯度达到99.2%。     

Anaerobic Biodegradation Tests of Poly(lactic acid) under Mesophilic and Thermophilic Conditions Using a New Evaluation System for Methane Fermentation in Anaerobic Sludge

Anaerobic biodegradation tests of poly(lactic acid) (PLA) powder were done at the thermophilic (55 °C) and mesophilic temperature (35 °C) under aquatic conditions [total solid concentrations of the used sludge were 2.07% (at 55 °C) and 2.24% (at 35 °C)] using a newly developed evaluation system. With this system, the evolved biogas is collected in a gas sampling bag at atmospheric pressure. This method is more convenient than using a pressure transducer or inverted graduated cylinder submerged in water. PLA was degraded about 60% in 30 days, about 80% in 40 days and about 90% in 60 days at 55 °C. On the other hand, the PLA degradation started in 55 days at 35 °C and degradation rate was much slower than at 55 °C.     

Modulating D-amino acid oxidase substrate specificity: production of an enzyme for analytical determination of all D-amino acids by directed evolution

Recent research on the flavoenzyme D-amino acid oxidase from Rhodotorula gracilis (RgDAAO) has revealed new, intriguing properties of this catalyst and offers novel biotechnological applications. Among them, the reaction of RgDAAO has been exploited in the analytical determination of the D-amino acid content in biological samples. However, because the enzyme does not oxidize acidic D-amino acids, it cannot be used to detect the total amount of D-amino acids. We now present the results obtained using a random mutagenesis approach to produce RgDAAO mutants with a broader substrate specificity. The libraries of RgDAAO mutants were generated by error-prone PCR, expressed in BL21(DE3)pLysS Escherichia coli cells and screened for their ability to oxidize different substrates by means of an activity assay. Five random mutants that have a 'modified' substrate specificity, more useful for the analytical determination of the entire content of D-amino acids than wild-type RgDAAO, have been isolated. With the only exception of Y223 and G199, none of the effective amino acid substitutions lie in segments predicted to interact directly with the bound substrate. The substitutions appear to cluster on the protein surface: it would not have been possible to predict that these substitutions would enhance DAAO activity. We can only conclude that these substitutions synergistically generate small structural changes that affect the dynamics and/or stability of the protein in a way that enhances substrate binding or subsequently catalytic turnover.     

Analysis of the kinetics of growth and lactic acid production for Lactobacillus helveticus growing on supplemented whey permeate

Growth of Lactobacillus helveticus on supplemented whey permeate was divided into five phases: lag, exponential, deceleration, stationary and decline phases. Each phase was characterized by simple model kinetics. From this and by considering a partial association of lactic acid production with growth, with an additional term introduced to account for cessation of production when the carbon substrate became limiting, the lactic acid production was analytically deduced for each growth phase. For both growth and production data, on the whole culture, the calculated values were found to match experimental data. All the model parameters can be easily deduced from experimental data. The model allows therefore a fine analysis of growth and production kinetics. Copyright © 2005 Society of Chemical Industry     

Application of silica gel as an effective modifier for the voltammetric determination of dopamine in the presence of ascorbic acid and uric acid

Amorphous silica gel modified carbon paste electrode (CPE) offers substantial improvements in voltammetric sensitivity and selectivity towards determination of dopamine (DA). Cyclic voltammetry of Fe(CN)₆^3−/4− as a negatively charged probe revealed that the surface of the silica gel modified carbon paste electrode had a high density of negative charge at pH 8.0. Therefore, the modified electrode adsorbed DA (pK_a = 8.9) and enhanced its voltammetric response while repulsed ascorbic acid (AA) (pK_a = 4.2) and uric acid (UA) (pK_a = 5.4) and inhibited their interfering effects. The influence of various experimental parameters including percent of silica gel in the CPE, pH of solution, and accumulation time and potentials, on the voltammetric response of DA was investigated. At the optimum conditions, the analytical curve was linear for dopamine concentrations from 2.0 × 10⁻⁷ to 1.0 × 10⁻⁶ mol L⁻¹ and 2.0 × 10⁻⁶ to 1.5 × 10⁻⁴ mol L⁻¹ with a detection limit (3σ) of 4.8 × 10⁻⁸ mol L⁻¹. The prepared electrode was used for determination of DA spiked into DA injection and human serum samples, and very good recovery results were obtained over a wide concentration range of DA.     

硫铁矿制酸装置低温位热回收系统的设计

介绍了奎屯铜冠冶化有限责任公司300 kt/a硫铁矿制酸项目干吸工序的低温位热回收系统的设计。详细分析了回收热水的低温位热回收系统的方案选择、工艺流程、设备及具体生产方案,并指出了优化设计中需要注意的几个问题。     

不同还原温度制备的石墨烯作为载体对甲酸电催化性能的影响

采用纳米石墨为原料,以3种不同还原温度80,60和40℃分别制得石墨烯GN-1、GN-2和GN-3。用3种不同还原温度制备的石墨烯作为载体制备了Pd催化剂Pd/GN-1、Pd/GN-2和Pd/GN-3。发现这3种钯催化剂Pd/GN-1、Pd/GN-2和Pd/GN-3中,Pd/GN-1具有最大的电化学比表面积,对甲酸的电催化氧化活性也最高,而Pd/GN-2电催化剂对甲酸电催化氧化的稳定性最好。     

9H-xanthene-2,7-diols as antioxidants for autoxidation of linoleic acid

The antioxidant activities of 9H-xanthene-2,7-diols and α-tocopherol were studied during the oxidation of linoleic acid in a homogeneous solution and in an aqueous micelle dispersion. The antioxidant activities of 9H-xanthene-2,7-diols for both systems were 1.0–2.4 times greater relative to α-tocopherol. In addition, the 1,3,4,5,6,8-hexamethylxanthene-2,7-diol showed less cytotoxicity toward human fibroblasts than did 2,6-di-t-butyl-4-methylphenol.     

Ag@CoFe2O4/Fe2O3 nanorod arrays on carbon fiber cloth as SERS substrate and photo-Fenton catalyst for detection and degradation of R6G

In this study, Ag nanoparticles loaded CoFe₂O₄/Fe₂O₃ nanorod arrays on carbon fiber cloth have been successfully fabricated by a hydrothermal route followed by a calcination treatment and photochemical reduction process. The as-prepared composite has been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The obtained Ag@CoFe₂O₄/Fe₂O₃ nanorod arrays show excellent SERS performance, which provides enhancement factors (EF) as high as about 1.2 × 10⁸ for Rhodamine 6G (R6G). The SERS signals collected over a 20?µm × 20?µm area show relative standard deviation lower than 12%, suggesting good SERS signal uniformity. In addition, the Ag@CoFe₂O₄/Fe₂O₃ nanorod arrays can be used as an effective photo-Fenton catalyst photocatalytical degradation of R6G. It was found that 99.15% of R6G can be degraded in an hour. This bifunctional composite that can act both as SERS substrates and as photo-Fenton catalyst would facilitate the cleaning and recycling of SERS substrates for reusing through a photocatalytic process, as well as facilitate the integration of rapid detection and effective degradation of organic pollutants.     

离子液体相转移催化氧化苯甲醛制备苯甲酸

以N-甲基咪唑、四氟硼酸铵、正丁醇、溴化钠为主要原料合成了1-正丁基-3-甲基咪唑四氟硼酸咪唑盐型离子液体。以该离子液体作相转移催化剂研究了双氧水氧化苯甲醛制备苯甲酸的反应。结果表明,该氧化反应中加入离子液体可起到溶剂及相转移催化剂的作用,当反应5 h时,苯甲醛可达最大转化率88%。反应后离子液体可回收再利用。