Microbial degradation of polyesters: Polycaprolactone degraded by P. pullulans

Polycaprolactone is degraded by the mold P. pullulans in the presence of other nutrients. The weight loss from solid polymer films covered by a nutrient agar gel on which colonies are growing is used to establish comparative rates of degradation. There is substantial loss (16 mg/cm² surface area) from a whole polymer of low (2,000) molecular weight in three weeks at 30°C. A high (30,000) molecular weight whole polymer degrades about 0.15 as much in the same time period. A fraction in the same range (38,000) but with a narrower molecular weight distribution shows no significant loss. This indicates that whole polymers of high molecular weight may lose only a portion of their distribution by microbial degradation in short-term tests. This hypothesis is tested by making mixtures of high (61,000) molecular weight with low (2,000) molecular weight polymer. Degradation is directly proportional to the low molecular weight content in these short-term tests with a single species of mold. Other workers have shown previously that in long-term, soil-burial tests, even a high (40,000) molecular weight polycaprolactone is essentially completely degraded after one year.     

高岭石固定化微生物对菲的降解研究

从新疆克拉玛依油田受污染土壤中分选筛出1株能够以菲为唯一碳源和能源生长的细菌(命名为XJB4),初步鉴定为苍白杆菌(Ochrobactrum sp.)。在初始pH 7.0,培养温度30℃,投菌比例10%时,菌株XJB4对菲(初始浓度50 mg/L)的降解率在9 d内达88%以上。采用吸附法可以将菌株XJB4固定在高岭石上,固定化微生物具有传质性好、耐毒害能力强特点,对菲的降解在72 h低浓度条件下可达到95.24%,优于游离菌对菲的去除率70.12%。     

高岭石固定化微生物对菲的降解研究

从新疆克拉玛依油田受污染土壤中分选筛出1株能够以菲为唯一碳源和能源生长的细菌(命名为XJB4),初步鉴定为苍白杆菌(Ochrobactrum sp.)。在初始pH 7.0,培养温度30℃,投菌比例10%时,菌株XJB4对菲(初始浓度50 mg/L)的降解率在9 d内达88%以上。采用吸附法可以将菌株XJB4固定在高岭石上,固定化微生物具有传质性好、耐毒害能力强特点,对菲的降解在72 h低浓度条件下可达到95.24%,优于游离菌对菲的去除率70.12%。     

混合菌降解氯苯酚类化合物

从驯化污泥中分离出一组能够降解氯苯酚类化合物的优势混合菌，在60h内能够将150mg／L的对氯苯酚完全降解。其最适降解条件：pH为6．0，温度为35℃，摇床转速240r／min。通过对降解过程的动力学分析，得出对氯苯酚的降解过程在不同的浓度范围内表现为零级反应关系。     

Anionic and nonionic surfactant sorption and degradation by algae cultures

Degradation of three surfactants has been determined by organic extraction procedures and infrared spectroscopy. Axenic cultures of five species of blue-green algae and three species of green algae which are common to waste stabilization ponds were test organisms. Analytical data are shown comparing the effects produced by the algae cultures and a heterogeneous microcosm. Linear alkyl sulfonate was the anionic surfactant compound tested. An alkyl polyethoxylate and an alkyl phenol polyethoxylate were the nonionic test surfactants. Sorption of the compounds by the algae usually was followed by release and degradation of up to 99% of some of the component parts of the surfactant molecule.     

一株苯酚降解菌的分离及降解特性

利用以苯酚为唯一碳源和能源的无机盐溶液作为驯化液,对某废水处理厂活性污泥进行驯化培养,从中分离筛选到1株苯酚降解菌,编号为BW-1.该菌株最高可耐受2000mg/L的苯酚.对该苯酚降解菌降解性能研究表明:该菌具有较强的苯酚降解能力,在35℃、pH值为6.0～7.5、装液量为60mL、接种量20%,摇床振荡速度120r/min的条件下,反应6h后可使400mg/L的苯酚降解率达80%以上;葡萄糖对菌体的生长及苯酚降解能力均有一定的影响;当葡萄糖浓度是600mg/L时,该菌对苯酚的降解率仍在60%以上.该研究对处理含有其它碳源的含酚废水具有一定的意义.     

混合菌群合成聚羟基脂肪酸酯研究进展

聚羟基脂肪酸酯（PHA）是微生物体内合成的可生物降解塑料,可以作为化学塑料的替代品。利用纯培养微生物发酵的合成方法由于使用葡萄糖等优质底物及过程需灭菌等原因,产品成本较高,严重制约了PHA的广泛使用;混合菌群利用废弃物合成PHA有效降低了纯培养方法的生产成本,因此受到人们越来越多的关注。本文对混合菌群合成PHA的历史沿革、合成原理、生产工艺、提取方法等方面进行了系统综述。回顾了混合菌群合成PHA的发展历程,简述了两种主要的合成机理,介绍了不同底物合成PHA的代谢途径,重点阐述了混菌合成PHA的三段式工艺和产物提取方法,同时也对新近的研究动态进行了分析总结。指出提高混菌浓度与利用实际废弃物的能力将成为未来研究的关键。     

光合细菌降解有机污染物的研究进展

利用微生物降解有机污染物是环境工程研究的热点之一。光合细菌(PSB)以其特有的生理特性和降解多种有机污染物的能力，日益受到了人们的重视。综述了光合细菌降解较复杂的有机污染物的种类、降解机理、有关的降解酶类和降解性质粒等方面的研究工作，为进一步扩大光合细菌实际应用展示了广阔的前景。     

硝化菌与反硝化菌混合培养生物脱氮的研究

从污泥中筛选得到了脱氮效率较高的硝化菌、亚硝化菌和反硝化菌,测定了其在含氮溶液中的生长曲线,计算得到其反硝化或硝化强度。将所得菌种在好氧条件下于模拟污水中进行混合培养,研究了脱氮效率及影响因素,并与用传统生物序列法进行硝化与反硝化培养脱氮的效果进行了比较。结果表明:混合培养硝化菌、亚硝化菌和反硝化菌过程中不会累积中间产物,生物脱氮率可达76.7%,较传统序列式脱氮法有显著提高,混合培养过程受pH值和温度的影响较小,是一种简易可行、高效和无污染的生物脱氮方法。     

Photocatalytic mineralization of phenol catalyzed by pure and mixed phase hydrothermal titanium dioxide

The photocatalytic mineralization of phenol catalyzed by pure (anatase, rutile) and mixed phase hydrothermal TiO₂ was studied in aqueous solution employing different oxidative agents, H₂O₂ and O₂. In the case of H₂O₂, rutile particles, having large dimensions and high aspect ratio (size: 30–70 nm × 150–350 nm), display the highest catalytic activity due to their low tendency to recombine electrons and holes generated by UV irradiation. By using water dissolved gaseous O₂, the catalytic TiO₂ activity generally decreases and rutile displays the lowest efficacy. In fact, oxygen preferentially chemisorbs at the surface of the nanosized particles of anatase (5–15 nm) and acts as effective electron scavenger, inhibiting the electron-hole recombination. The number of electron and hole traps (Ti³⁺, O₂⁻ and O⁻) and the rate of formation of the short-lived hydroxyl radicals OH under UV irradiation, were evaluated by electron paramagnetic resonance (EPR). A correlation was suggested among the amount of the charge carrier centers, the rate of formation of OH radicals and the catalyst photoactivity. This confirms that the photocatalytic properties depend on the possibility that electrons and holes separately interact with the oxidative agents at the TiO₂ surface, inducing the formation of OH radicals.     

Cathodic degradation mechanisms of pure Sn electrocatalyst in a nitrogen atmosphere

The application of electrocatalysts used at high cathodic overpotentials for the electrochemical reduction of pollutant species such as CO₂ has revealed a lack of understanding of the cathodic degradation mechanisms of those materials. Pure Sn is one of the most relevant candidate materials mainly because of its high selectivity for the reduction of CO₂ to formic acid and formate salts. Degradation of the electrocatalyst can arise from a combination of cathodic polarization and induced changes to the surface by CO₂ reduction products. In this study, the cathodic degradation mechanisms of pure Sn were studied as a function of rotation rate, time, current density, electrolyte concentration, grain size, and orientation in a nitrogen-saturated atmosphere using a rotating disk electrode. Several degradation morphologies were observed, but three were dominant. In the first type, electrochemical alterations of grains with specific orientations produced substantial weight changes, both losses and gains. The second type resulted in an alkali-rich deposit that had a high coverage but produced small weight changes. The third type consisted of carbon-rich stains that typically had a small coverage.     

Transformation of Reichstein's compound S into prednisolone by immobilized mixed cultures

Reichstein's compound S was transformed into prednisolone in a single-step fermentation using immobilized mixed cultures, entrapped in different gels or adsorbed on clay particles. Calcium alginate at a gel concentration of 2% gave the highest transformation activities and prednisolone yields. The entrapped mixed cultures could be repeatedly used in batch-wise transformation for at least six times when suspended in diluted nutrient medium and for three times when suspended in distilled water; in the latter case the entrapped cultures required to be reactivated in nutrient medium for further reuse. Mixed cultures adsorbed on clay particles were successfully reused 18 times, with reactivation after the 9th and 15th uses. Continuous transformation of substance S into prednisolone by mixed cultures adsorbed on clay particles was more efficient than batch-wise reused adsorbed cultures and was dependent on the daily working medium volume.     

Robust adaptive control of yeast fed-batch cultures

Model-based control of bioprocesses is a difficult task due to the challenges associated with biological system modeling and the lack of on-line measurements. In this study, two robust controllers using minimal a priori process knowledge and minimal measurement information are designed to maximize biomass productivity in aerobic cultures of Saccharomyces cerevisiae. This latter objective can be achieved through the regulation of the ethanol concentration at a low constant value. The linearization of Sonnleitner’s model allows simple transfer function models to be derived, which describe the relation between the ethanol concentration, the substrate feed and an exponential disturbance – image of the substrate demand for cell growth – in the different operating (respirative and respiro-fermentative) regimes. The two controllers are based on these linear models and use a RST structure, but differ in the way the exponential growth disturbance is handled. In the first controller, the disturbance is represented by a linear model, whereas in the second controller, the disturbance is measured on-line via the oxygen transfer rate signal and a feedforward control action is used to cancel the disturbance effect on the ethanol concentration. Particular attention is paid to the robustification of the controllers to measurement noise, neglected high frequency dynamics and uncertain stoichiometry coefficients using the observer polynomial. Tests in simulation show the controller performance.     

混合脂肪酸选择性加氢制高纯度油酸

高纯度油酸是重要的精细化工产品。混合脂肪酸选择性加氢在化学工业中是一个非常重要的环节,同时也是生产高纯度油酸的合理途径。以雷尼镍作催化剂对混合脂肪酸进行选择性加氢正交试验和单因素水平试验,对所得产品进行凝固点测定和韦氏法碘值测定后得出最佳反应条件：在温度200℃、压力0．6MPa、时间1h、催化剂ω（B）=0．6％、搅拌250r／min的条件下可使混和脂肪酸碘值从120．84降到100左右,反应前后凝固点变化不大,提高了油酸的纯度。     

Influence of C18 long chain fatty acids on butyrate degradation by a mixed culture

Butyrate degradation in the presence of C₁₈ long chain fatty acids (LCFAs) was examined under anaerobic conditions at 21 °C. Butyrate degradation rates were a function of linoleic acid (LA) and oleic acid (OA) concentration but independent of the amount of stearic acid (SA) added. Within 2–4 h, butyrate reached undetectable levels in the control cultures. However, in cultures fed with LA, butyrate was removed within between 12 and 25 h and within 2–12 h for cultures inoculated with OA or SA. Propionate was detected in cultures fed with 50 mg dm^?3 LA and in cultures inoculated with OA and SA. LA exerted a greater inhibitory effect on butyrate‐degrading organisms than OA and SA with longer removal times observed in cultures fed with LA. The propionate and acetate removal times and quantity produced were not related to the type and concentration of LCFA. Copyright © 2004 Society of Chemical Industry     

The solubility of cefquinome sulfate in pure and mixed solvents

Solid-liquid equilibrium data of cefquinome sulfate is important to develop industrial crystallization processes for cefquinome sulfate. The solubilities of cefquinome sulfate in five pure solvents (methanol, ethanol, ethylene glycol, acetic acid and water) from 277.15 to 305.15 K and in a binary acetone-water solvent from 278.15 to 293.15 K were measured at atmospheric pressure. The pure-solvent solubility data was correlated to the modified Apelblat and Van’t Hoff equations whereas the mixed-solvent system data was correlated to the modified Apelblat, Van’t Hoff, CNIBS/R-K and Jouyban- Acree models. It was found that the solubilities of cefquinome sulfate in all tested solvents decreased with the increasing of temperature. In addition, the thermodynamic properties of the dissolution processes, including standard Gibbs free energy, enthalpy and entropy changes, were calculated using the Van’t Hoff equation. It was found that the dissolution of cefquinome sulfate is exothermic.

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原油降解菌的分离及其降解性能

从大港油田的石油污染土壤中筛选出一株高效原油降解菌株X3,研究了该菌株对原油的降解能力,比较了不同浓度下的原油对细菌生长和降解率的影响,同时还研究了pH值和盐浓度对该菌株降解原油能力的影响.研究结果表明该菌株具有一定的耐碱性和耐盐性,原油浓度对总石油烃(TPH)的降解速率有很大影响,在30℃、原油初始浓度为1000mg/L、pH值为7、NaCl浓度为5g/L的条件下,该菌株对原油的去除效果最佳,可达到72.6%.色谱分析表明碳数是影响石油烃组分降解的最大因素,碳教越大降解越难进行.     

BAF投加优势菌深度降解焦化废水的试验研究

采用投加了优势菌的曝气生物滤池（BAF）对焦化废水进行深度处理,考察温度、pH值、气水体积比、回流比对系统的影响。试验结果表明：最佳温度为25～35℃、pH值为7～8、最佳气水体积比为3∶1、最佳回流比为1∶1,系统出水CODCr的质量浓度达到GB 8978—1996《污水综合排放标准》的二级标准（ρ（CODCr）〈120 mg/L）、NH3-N的质量浓度达到GB 8978—1996的一级标准（ρ（NH3-N）〈15 mg/L）。BAF投加优势菌深度降解焦化废水效果明显,有很好的发展前景。     

pH and Eh control of cultures of sulphate-reducing bacteria

Batch cultures of Desulfovibrio vulgaris, carried out in a 5-litre stirred fermenter, are described. Bacterial counts and sulphide formation are reported for experiments carried out under a selection of controlled Eh and pH conditions. Specific growth and sulphide formation rates are determined and compared. Variations in the growth rates under the different controlled conditions are examined and discussed in terms of product inhibition by sulphide. A relatively high specific rate of exponential growth was observed at Eh = - 150 mV and pH=6.95, when sulphide inhibition was believed to be at a minimum.