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.     

利用纤维素水解液中的纤维二糖发酵制备丁二酸

纤维素水解液中通常含有纤维二糖。本文考察了Actinobacillus succinogenes NJ113利用纤维二糖厌氧发酵生产丁二酸的能力,并利用蔗渣纤维素制备纤维二糖作为碳源用于厌氧发酵生产丁二酸。3 L发酵罐厌氧发酵结果显示：以35 g/L纤维二糖作为碳源发酵制备丁二酸,其产量为23.51 g/L,产率达到67.17%;用含有18 g/L纤维二糖和17 g/L其它糖类的蔗渣纤维素水解液作为碳源发酵制备丁二酸,丁二酸的产量和产率分别为20.00 g/L和64.73%。因此,Actinobacillus succinogenes NJ113具有较强的利用纤维二糖生产丁二酸的能力,而且利用废弃的纤维素制备纤维二糖作为碳源高效、经济地发酵制备丁二酸具有可行性。     

硫酸催化葡萄糖制备乙酰丙酸的过程强化

采用高温下稀硫酸催化葡萄糖的方法制备乙酰丙酸。考察了反应温度、硫酸浓度和搅拌转速对葡萄糖转化率和乙酰丙酸收率的影响,并优化确定了最优反应条件。进一步,分析了最优反应条件下不同葡萄糖初始浓度对乙酰丙酸收率的影响。为了提高高浓度葡萄糖底物反应时乙酰丙酸的收率,采用两种不同的补料方法进行实验：分3次,依次加入7%、6%与5%的葡萄糖;每次均添加3%的葡萄糖,共6次。结果表明：①提高硫酸浓度、反应温度和搅拌速度有利于加快葡萄糖转化和乙酰丙酸生成;②高浓度葡萄糖底物不利于乙酰丙酸的生成,且浓度越高,乙酰丙酸收率越低;③通过补料操作,可使乙酰丙酸收率由 44.3%提高至65.9%。     

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.     

Solvent extraction and purification of sugars from hemicellulose hydrolysates using boronic acid carriers

Research was performed to determine whether it was technically feasible to use boronic acid extractants to purify and concentrate the sugars present in hemicellulose hydrolysates. Initially, five types of boronic acids (phenylboronic acid, 3,5‐dimethylphenylboronic acid, 4‐tert‐butylphenylboronic acid, trans‐β‐styreneboronic acid or naphthalene‐2‐boronic acid) dissolved in an organic diluent (Shellsol^® 2046 or Exxal^® 10) containing the quaternary amine Aliquat^® 336 were tested for their ability to extract sugars (fructose, glucose, sucrose and xylose) from a buffered, immiscible aqueous solution. Naphthalene‐2‐boronic acid was found to give the greatest extraction of xylose regardless of which diluent was used. Trials were then conducted to extract xylose and glucose from solutions derived from the dilute acid hydrolysis of sugar cane bagasse and to then strip the loaded organic solutions using an aqueous solution containing hydrochloric acid. This produced a strip solution in which the xylose concentration had been increased over 7× that of the original hydrolysate while reducing the concentration of the undesirable acid‐soluble lignin by over 90%. Hence, this process can be exploited to produce high concentration xylose solutions suitable for direct fermentation. Copyright © 2004 Society of Chemical Industry     

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.     

疏水性钯纳米团簇的合成及其作为表面增强拉曼散射基底的应用

以醋酸钯为前体、有机氢硅烷为还原剂开发了一种简单温和的疏水性钯纳米颗粒制备方法。通过调节前体、保护剂和还原剂的配比,在氯仿溶液中室温条件下合成了疏水性的钯纳米团簇和钯纳米球。运用透射电子显微镜（TEM）、X射线衍射（XRD）、光学接触角测试仪、循环伏安法（CV）、表面增强拉曼光谱（SERS）对这两种钯纳米材料进行了测试表征。TEM观察表明这两种钯纳米材料粒径分布均匀,分散性良好。接触角测试表明钯纳米团簇与钯纳米球均具有疏水性。CV测定结果显示这两种钯纳米材料具有良好的电催化稳定性,钯纳米团簇比钯纳米球对乙醇氧化具有更突出的电催化性能,表明钯纳米团簇结构稳定并具有更大的比表面积。SERS测试表明钯纳米团簇是一种优良的疏水性表面增强拉曼散射基底,利用这种基底对疏水性致癌物3,4-苯并芘和联苯胺进行了SERS快速检测,检测限为0.1mg/mL。     

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.     

代谢控制发酵产琥珀酸研究进展

琥珀酸作为一种重要的化工原料被广泛应用于现代工业的各个领域,具有庞大的市场需求。利用生物法发酵生产琥珀酸因具有资源可再生利用、绿色清洁节能等方面不可替代的优势而成为当今研究的热点。本文从代谢调控的角度出发分析总结了一些产琥珀酸菌株,尤其是重组大肠杆菌在发酵生产琥珀酸中所应用到的方法和策略,如对代谢途径中关键酶的调控以及发酵生产中的关键因素(如氧化还原回复力调控、CO₂调节、代谢途径改造等),着重突出了代谢控制发酵生产方面的研究进展,并对今后的发展方向提出了一些设想。     

Use of trifluoromethanesulfonic acid as catalyst for the cyclization of polyisoprene

In this study, trifluoromethanesulfonic acid was employed as catalyst for the cyclization of polyisoprene. From ¹H nuclear magnetic resonance spectroscopy and gel permeation chromatography investigations, cyclization was confirmed, and the molecular structure variation of polyisoprene during cyclization reaction was determined. With the comparison to that catalyzed by other strong acids (methanesulfonic acid), polyisoprene was cyclized with much higher efficiency, using trifluoromethanesulfonic acid as catalyst. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3666–3669, 2006     

Performance comparison of precipitation strategies for recovering succinic acid from carob pod-based fermentation broths

ABSTRACT

Experiments were performed for comparing and selecting the most appropriate precipitation strategy for succinic acid (SA) recovery from carob pod extract fermentation broths. The performances of three downstream options – employing calcium hydroxide, magnesium hydroxide or ammonia – were investigated and compared from operational, techno-economical and sustainability viewpoints. The highest SA recovery (84.3%) was obtained with ammonia, whereas the calcium-based treatment proved inadequate. Sustainability indicators favoured magnesium-based treatment, closely followed by the ammonia-based one. A preliminary economic analysis favours magnesium-based treatment, which appears to be the most feasible option. However, materials recycling and possible by-products commercialization could well position also ammonia-based treatment.     

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.     

代谢工程改造大肠杆菌生产琥珀酸

琥珀酸（succinic acid）是一种四碳二羧酸,在食品、医药、塑料和化工行业具有广泛的应用。目前,微生物法生产琥珀酸存在得率低、生产强度低、副产物积累等问题。为此,本研究通过复合诱变（ARTP和⁶⁰Co-γ射线）筛选到一株耐高渗突变株FMME-N-2,其琥珀酸得率为0.70g/g葡萄糖,同时积累18.8g/L乳酸、7.6g/L甲酸和17.3g/L乙酸。为了提高琥珀酸得率,通过敲除乳酸脱氢酶基因（ldhA）、丙酮酸-甲酸裂解酶-甲酸转运蛋白基因（pflB-focA）、磷酸转乙酰基基因（pta）、丙酸激酶基因（tdcD）和a-酮丁酸甲酸酯裂解酶基因（tdcE）,阻断冗余代谢支路减少副产物积累,获得工程菌株FMME-N-13,琥珀酸得率增加到0.92g/g葡萄糖,同时副产物大大降低,积累0.6g/L乳酸、3.6g/L甲酸和12.3g/L乙酸。同时,通过调控RBS强度组合优化来自产琥珀酸放线杆菌的磷酸烯醇式丙酮酸羧激酶基因（AsPCK）和来自博伊丁假丝酵母的甲酸脱氢酶基因（CbFDH）的表达水平,调控胞内ATP和NADH的浓度,最优工程菌FMME-N-26（FMME-N-13-L-AsPCK-L-CbFDH）的琥珀酸得率增加至1.04g/g葡萄糖,仅积累5.5g/L乙酸;最终,对厌氧阶段葡萄糖浓度进行优化,当葡萄糖浓度控制在0~5g/L时,菌株FMME-N-26的琥珀酸浓度增加到111.9g/L,得率为1.11g/g葡萄糖（理论产率的99%）,生产强度为1.76g/L/h,为琥珀酸的工业化生产奠定了良好的基础。