Release of genetically modified micro-organisms into the environment

Biotechnology in general, and recombinant DNA technology in particular, has the capacity to change the health and wealth of every individual, but like other major advances in science and technology such as nuclear power and electronics it can also be exploited to mankind's detriment. For this reason and the fact that recombinant DNA technology involves altering the molecules encoding life itself, the subject has given rise to a high level of public debate. Centuries of experience with the release of conventional micro-organisms for sewage treatment, agriculture and food production have shown that the release of large numbers of foreign organisms into an environment does not necessarily cause ecological damage. In fact few of these organisms survive for long periods. The threat of horizontal gene transfer from recombinant organisms to indigenous ones is however very real and mechanisms exist whereby, at least theoretically, any genetically engineered trait can be transferred to any prokaryotic organism and many eukaryotic ones. The rapid spread of antibiotic-resistant organisms since the widespread introduction of antibiotics graphically demonstrates that such a threat is real. There have now been several experiments to determine the effect of environmental release of micro-organisms, both in enclosed areas and in unenclosed sites. Proposals for the use of genetically modified micro-organisms that contain specific gene deletions have had a relatively smooth passage through government approval agencies and public enquiries and some products have been approved for commercial use. In addition a strain of bakers' yeast with an altered control element has also been approved for commercial use in the UK. Genetically modified viruses, especially those containing foreign genes have not received such favourable treatment and have been the subject of heated national and international debate. Many microbiologists are convinced, however, that the use and release of carefully constructed genetically engineered organisms will result in significant benefit, but with little risk to the environment. Ecologists, however, are not so sanguine and in the current ‘green’ political atmosphere their opinions are very influential. Thus most developed countries now have in force a series of very cautious regulations and guidelines for the release of genetically modified micro-organisms.     

Influence of surface characteristics on the adhesion of Alcaligenes denitrificans to polymeric substrates

The adhesion of Alcaligenes denitrificans to several polymeric materials was investigated. As the nature of the surfaces of the micro-organisms and the substrate materials is an important factor in the adhesion process, characteristics such as the electrokinetic potential and hydrophobicity were also determined and correlated with the capacity of bacterial cells to adhere to solid surfaces. The substrates used were high-density polyethylene (HDPE), polypropylene (PP), poly(vinyl chloride) (PVC), and poly(methyl methacrylate) (PMMA). The electrokinetic potential of the cells and the substrates was determined by measurements of electrophoretic mobility and the hydrophobicity was determined by contact angle measurements. All the substrates studied as well as the bacterial strain have a negative zeta potential, which means that adhesion is not mediated by electrostatic interactions. As far as hydrophobicity is concerned, PP is the most hydrophobic material, PMMA is the least hydrophobic, whereas HDPE and PVC present an intermediate behavior. As bacteria cells are hydrophilic, adhesion is favored to PP; therefore, this substrate material seems to be the one that promotes a stronger adhesion and the development of the most stable biofilm for use as a biomass carrier in denitrifying inverse fluidized bed reactors. This was confirmed by the results of adhesion tests. In this way, adhesion seems to be dominated by hydrophobic interactions.     

Macrocomposites made by injection molding

Macrocomposites can be prepared by injection molding an engineering resin into a mold which contains an insert of a different engineering resin. Using 3/8-inch beams and 1/4-inch disks as model systems, we have shown that macrocomposites give parts with combinations of stiffness and toughness far superior than can be made by conventional injection molding of a single material. The key to making macrocomposites with good properties is to have the insert sufficiently hot so that the surface is melted during the second molding step. The toughness of a macrocomposite can be derived not only from proper positioning of a tough material and a stiff material, but also from more effective orientation of glass fibers resulting from the alteration of the mold cavity caused by the insert. Before macrocomposites can be commercialized, significant technical obstacles with respect to both molding equipment and part design procedures must be overcome.     

Influence of mechanical stress on the growth of Rhizopus nigricans in stirred bioreactors

This investigation was undertaken in order to examine the factors affecting mechanical damage to micro-organisms in stirred bioreactors. Growth of the mould Rhizopus nigricans was studied in stirred bioreactors at different geometrical and operating parameters. Since experimental results cannot be described by conventional key parameters, a new concept has been suggested. It is based on the analogy to processes of mechanical disintegration. It is shown that the same key parameter, i.e. the ratio of power input to flow rate, can be used for a satisfactory correlation of experimental data on mechanical damage to micro-organisms, which is an important step in the recovery of intracellular products in biotechnology.     

Surface characterization of glass and poly(methyl methacrylate) soiled with a mixture of fat,oil, and starch

Micro-organisms on food contact surfaces provide a 'biotransfer potential', i.e. the ability to contaminate foods during processing or preparation. Surfaces coated with organic materials can act as sites for microbial attachment. This investigation into the surface properties of glass and poly(methyl methacrylate) substrates soiled with a milk powder, oil, and starch composite has found that fatty acid esters dominate the surface chemistry. A lower concentration of proteinaceous material was also detected, with the concentration dependent on both the underlying substrate and the thickness of the soiling material. The physical surface structure of the fouled surfaces showed a complicated surface topography with features of the order of tens of micrometres wide and up to 2 μm high, which increased in size with increasing thickness of the soiling layer. The features reflect bulk incompatibilities between the components of the soiling material and demonstrate the heterogeneity of the surface as presented to micro-organisms.     

Studies related to the structure and reactivity of coals 17. The chemical structure of asphaltenes and residues from reactions of Victorian brown coals

The chemical structures of the asphaltenes and residues from reactions of a range of brown coals with widely varying atomic H/C ratios have been examined by chemical and spectroscopic methods, and have been shown to be remarkably consistent. Asphaltenes and residues from brown coals with high atomic H/C ratios show a small but significant increase in incorporation of aliphatic, guest material although the main bulk of material is derived from the host component of the coal (i.e. ligno-cellulosic or tannin derived material).     

改良氧化沟活性污泥ORP的调控及对磷吸收/释放的影响

对改良的Carrousel氧化沟活性污泥的氧化还原电位(ORP)变化进行了研究,结果表明,在非严格厌氧状态下磷难以释放,同时ORP也不会降低。在外加有机物且厌氧的条件下,新鲜污泥的ORP会明显降低,一般可以达到-80～-150 mV,且存在显著的磷释放,ORP降低的程度与有机物的浓度和种类无明显关系。微生物活性降低后,外加挥发性脂肪酸,ORP不会显著降低,说明对于EBPR系统来说,ORP的高低取决于微生物厌氧代谢的速率。     

Biotechnology as Applied to the Oils and Fats Industry

Three areas where biotechnology is applicable to the oils and fats industry are described. 1. Biotechnology and oil plants includes the cloning of high-yielding trains of oil palms to yield progeny in large numbers relatively quickly. Mutation of oilseeds to change the fatty acid composition is also being carried out in various laboratories. 2. Biotechnology with enzymes encompasses the use of microbial lipases for the interesterification of triacylglycerols to form cocoa butter substitutes, as well as the use of lipases to hydrolyse selectively particular fatty acyl esters. Some industrial developments in these areas appear imminent. 3. Biotechnology with micro-organisms can be seen as an alternative means of producing oils and fats to existing routes though the economics are against such processes being taken up for all but the most expensive oils and fats. A range of oils can, however, be produced by bacteria, algae, yeasts and moulds. Micro-organisms can also be used to transform alkanes and fatty acids to provide various fatty acid derivatives which could be of value. The biochemistry behind lipid accumulation is described. This provides an understanding of the regulatory enzymes which need to be controlled in order to achieve high accumulations of lipids. From such information, it then becomes possible to consider metabolic manipulation of the organism to improve its fat yield. By extension of these arguments, possible opportunities for genetic engineering into both micro-organisms and plants then become evident.     

Challenging zircon coatings by suspension plasma spraying

Zircon is a ceramic material that decomposes at high temperature, limiting its use by conventional thermal spraying. In this work, it is intended to use thermal spraying from concentrated aqueous suspensions to evaluate the possibility of obtaining coatings in which a significant proportion of zircon could be preserved. For this purpose, stable concentrated suspensions of zircon have been prepared, which have been subsequently sprayed at two different spraying distances. The coatings were characterised in terms of microstructural features and the amount of zircon present in the coatings was quantified. All the coatings obtained display the typical microstructure derived from the deposition of liquid feedstocks by plasma spraying. In all cases, the XRD analysis demonstrates the partial decomposition of zircon into zirconia and residual silica, but also that a significant percentage (about 20%) is preserved without decomposing, which marks a strong difference with respect to reported data for atmospheric plasma spraying.     

Mikrobiologische Probleme bei der Bestrahlung von Fish

Microbiological Problems in the Irradiation of Fish Sea-fish contain very few micro-organisms immediately after hauling; micro-organisms are located mainly on the skin. It is advisable to carry out the radiopasteurization immediately after the haul. Experiments have been carried out on the irradiation of freshly hauled East Sea cod, and perch with a high microbial content. Effects of a first irradiation at doses of 50 and 100 krad, and those of a second irradiation after eight days at a level of 50 krad on bacterial count, content of volatile bases, and pH-value are reported. The influence of the aforesaid treatment followed by storage in ice on the possible growth of Cl. botulinum is discussed.     

含氮磷高分子肥料的制备和结构研究

水溶性合成高分子聚合物能被微生物分解,是一种优良的土壤改良剂,并对土壤营养元素有良好的吸附作用,可减少元素流失,提高肥效。合成了一种营养元素高分子缓释化肥,将含氮磷的降解水溶性高分子材料引入到化肥领域,并通过实验研究不同的反应工艺条件对高分子肥料结构和含氮磷肥效的影响。     

The mechanisms of free surface segregation

When a heap is formed by pouring, free surface segregation is the process by which free flowing particles separate. Experiments were conducted in an apparatus in which all variables could be controlled and the results could be expressed in dimensionless form. Data were obtained principally for small quantities of a tracer component in a close-sized bulk material. Both diameter and density had a significant effect on the spatial probability distribution of the tracers. Those larger than the bulk or less dense would float down to the bottom of the free surface, whereas those smaller than the bulk or more dense would sink into the heap close to the pouring point. Improvement in distribution could be achieved by balancing the effects of size and density. Increase in the velocity of impact onto the surface affected the influence of size but not of density. The spatial distribution of the tracer in the feed material was also significant.     

Microbiological deterioration of rubbers and plastics

The effects of micro-organisms on rubbers and plastics are reviewed, with reference to the chemical nature of the polymers and their possible additives. The confused and sometimes contradictory nature of the evidence is indicated, and it is concluded that both synthetic and naturally-occurring polymers are attacked but it is not possible at this stage to say which chemical groups in each polymer are susceptible.     

Effect of biochemical treatment on the adhesion of poly-p-amidobenzimidazole fibre

In order to improve the interaction between the reinforcement and the matrix binder, fibre surface modification with micro-organisms is proposed. Enzymatic hydrolysis of surface macromolecules in aramid fibres leads to the formation of carboxyl groups. If an aqueous solution containing polyvinyl alcohol is the nutrient for the micro-organisms, hydrolysis is followed by the grafting of alcohol molecules onto the fibre surface through etherification. The fibre strength does not deteriorate, but the morphology and the chemical nature of the surface undergo alterations. As a result, wetting by molten thermoplastics is improved. The three-fibre method was used to investigate the adhesion between poly-p-amidobenzimidazole fibres (unmodified and modified) and thermoplastic matrices (polysulphone and polycarbonate). The biochemical treatment almost doubled the bond strength. Examination of the modified fibres, separated from the matrices, by scanning electron microscopy indicated the presence of a diffuse interphase between the fibre and the matrix. In the case of untreated fibres, the adhesional contact failed through interfacial shear; however, with modified fibres both were observed: interfacial shear and cohesive failure in the fibre. Thus, biochemical modification seems to be a simple method for fibre treatment to promote the compatibility of fibres and matrices, and to increase the composite strength.     

飞秒激光诱变微生物技术及其机理的研究进展

飞秒激光诱变微生物是一项崭新的技术。本文针对传统低功率He-Ne激光诱变微生物的优点和缺点,结合飞秒激光光束脉冲持续时间短、瞬时功率大、聚焦尺寸小的优点,简要概括了国内外对飞秒激光诱变微生物技术的研究。同时对飞秒激光辐射微生物过程中多光子吸收、形成等离子体、产生生物活性氧、DNA损伤自身修复等一系列的机理研究进行了总结。最后,对飞秒激光诱变微生物技术及其机理研究进行了展望并提出了建议：结合关键酶活性测定和动力学参数测定来选择飞秒激光诱变的技术参数。     

纳米氧化铝与赤藻糖醇复合相变材料的实验研究

赤藻糖醇是一种极具潜力的相变材料但很容易发生过冷。文中通过添加纳米材料作为成核剂改善赤藻糖醇的性能,制备了不同纳米材料的相变复合材料。对样品的融化-凝固过程进行观测记录,绘制了时间温度曲线并对导热系数和相变潜热进行测定,分析了添加材料对赤藻糖醇的影响。结果表明:在简单的超声振荡分散方式下添加纳米氧化铝可以很好地分散于融化的赤藻糖醇基液中。添加的纳米氧化铝能有效缓和赤藻糖醇的强过冷倾向;当添加质量分数为0.25%的纳米氧化铝时材料的导热系数较纯赤藻糖醇提高2倍,且相变潜热不发生较大变化。     

EFFECT OF MICROBIAL ADSORPTION AT THE GAS/LIQUID INTERFACE ON OXYGEN ENHANCEMENT FACTORS

The adsorption of micro-organisms at the gas/liquid interface causes both an increase in the oxygen respiration rate and a decrease in the oxygen diffusion coefficient near the interface. An increase in the oxygen consumption rate increases the oxygen mass transfer rate into the bacterial broth but a decreased oxygen diffusion coefficient reduces the mass transfer rate. These two factors must be taken into account when enhancement factors are calculated.     

EFFECT OF MICROBIAL ADSORPTION AT THE GAS/LIQUID INTERFACE ON OXYGEN ENHANCEMENT FACTORS

The adsorption of micro-organisms at the gas/liquid interface causes both an increase in the oxygen respiration rate and a decrease in the oxygen diffusion coefficient near the interface. An increase in the oxygen consumption rate increases the oxygen mass transfer rate into the bacterial broth but a decreased oxygen diffusion coefficient reduces the mass transfer rate. These two factors must be taken into account when enhancement factors are calculated.     

湿法烟气脱硫技术研究现状及进展

介绍了国内外已工业应用的主要湿法烟气脱硫技术,如石灰石/石灰-石膏湿法、海水烟气脱硫和微生物法等工艺技术的应用现状及研究发展,并对近年来国内外发展的脱硫新工艺进行了评述。由此探讨了湿法烟气脱硫技术现在存在的问题、研究情况和发展前景。     

Microbial inactivation by high-pressure

High-pressure treatments are receiving a great deal of attention for the inactivation of micro-organisms in foodstuff processing, pressure instead of temperature is used as stabilizing factor. In this context, high hydrostatic pressure treatment is the most studied alternative process, many works reported successful results in inactivating a wide range of micro-organisms under different operative conditions such as temperature, cycles of pressure, exposure time. Furthermore, a number of processes using high pressure treatment (HPT) has already been put into the market. Nevertheless this new technology presents the main limitation to be very expensive and difficult to control and manage because of the extremely high pressure employed, so that the widespread industrial diffusion in industry field appears cumbersome. The treatment with supercritical CO₂ could become a relevant alternative to HPT in the field of microbial inactivation of food as well as an innovative technique for the sterilization of thermally and hydrolytically sensitive polymeric materials in biomedical applications, such as polymeric particles for drug delivery or polymeric implants. It has been demonstrated that the effect of microbial inactivation assuring healthy food preservation is already consistent at pressures moderated (lower than 200 bar) when compared with those employed by traditional hydrostatic-pressure HPT methods (2000–7000 bar). In this work the anti-microbial potential of compressed CO₂ was investigated against gram-negative bacteria, gram-positive bacteria and spores; as model species, Pseudomonas aeruginosa, Bacillus subtilis and spores of B. subtilis were used. The experiments were performed in a semi-continous apparatus at different but mild operative conditions. Excellent results were obtained for micro-organisms, under appropriate conditions the survival ratio of bacteria could be reduced to about seven orders of magnitude. Inactivation of spores under the same conditions, found to be conflicting in open literature, was not satisfactory. Spore inactivation was possible by coupling combination of higher temperature and longer contact time conditions. The application of pressure cycles was also found to be beneficial.