生物表面活性剂对黄土中菲的增溶作用

研究了生物表面活性剂皂角苷(Saponin)和两种常见的化学合成非离子表面活性剂TritonX-100和Brij35对吸附在黄土上菲的增溶萃取作用。试验表明皂角苷对菲有明显的增溶作用,水溶液中菲的表观溶解度与皂角苷浓度成线性增加关系。与化学合成非离子表面活性剂TritonX-100和Brij35相比,在水体系和水-土体系中皂角苷均有较高的质量增溶比(SR)和胶束假相和水相的分配系数(Kmc)。同时发现浓度较低(小于CMC)时,皂角苷在黄土上的吸附很小。结果表明生物表面活性剂有望替代化学合成表面活性剂用于污染土壤的修复。     

两株抗铜细菌的筛选、鉴定及对碳酸铜的溶解作用

本研究从长期受铜污染的铜矿废弃地土壤中分离得到两株对重金属铜具有较强抗性的菌株F16a和Fw17a。对菌株形态、生理生化特性及其16S rDNA系统进化进行分析,将F16a鉴定为肠杆菌属(Enterobacter),Fw17a鉴定为假单胞菌属(Pseudomona)。F16a和Fw17a对氨苄青霉素、头孢他啶均有抗性;此外,Fw17a还对氯霉素、四环素及低浓度的卡那霉素具有抗性。在有氮培养基(含500 mg/L CuCO3)液体培养48 h后,F16a使培养基上清液中铜浓度增加了300%左右;相反,Fw17a使培养基上清液中铜浓度降低了60%左右。     

Reducing the dietary protein:energy (P:E) ratio changes solubilization and fermentation of rainbow trout (Oncorhynchus mykiss) faeces

Nutrients discharged from aquaculture industries can detrimentally affect water recipients, and this problem must be addressed if the production is to be decoupled from the natural environment. Denitrification is a process by which nitrate is removed using soluble, readily biodegradable carbon compounds. Hydrolysis and concomitant fermentation of organic solids produces such soluble carbon compounds e.g. in the form of volatile fatty acids (VFAs). The current study examined the hydrolysis and the production of VFAs, the carbon:nitrogen ratio (C:N), and the release of nutrients (phosphorus and ammonium) from hydrolyzing and fermenting settable faecal solids (SFS) obtained from rainbow trout (Oncorhynchus mykiss). Triplicate tanks of fish were fed five isoenergetic experimental diets with different protein:energy (P:E) ratios: 15, 17, 19, 21, and 23. The SFS from four consecutive days were collected and pooled prior to incubation in 15, 1 L anoxic/anaerobic batch reactors maintained at 20 ± 2 °C and continuous magnetic stirring. Daily samples from the batch reactors were obtained for 7 successive days and analyzed for total ammonia nitrogen (TAN), phosphorus expressed as orthophosphate (PO₄³⁻-P), VFA, and soluble COD (sCOD). The results showed that the two lowest P:E ratio diets (i.e. 15 and 17) produced SFS with a significantly higher degree of solubilization measured as sCOD:total chemical oxygen demand (TCOD), compared to the higher P:E ratio diet 21 (0.30–0.29 versus 0.24 g sCOD/g TCOD). Inversely, SFS deriving from the lowest P:E ratio diet (i.e. 15) displayed the lowest degree of fermentation measured as VFAs/sCOD, compared to SFS deriving from the four higher P:E diets (0.36 versus 0.51–0.56 g VFA/g sCOD). In the same way, the lowest P:E diet showed a significantly lower solubilization of nitrogen measured as TAN:total Kjeldahl Nitrogen (TKN) compared to the three highest P:E diets (i.e. 19–23; 0.14 versus 0.26–0.34 g TAN/g TKN). The two lowest P:E diets (i.e. 15–17) showed on the contrary the highest solubilization of phosphorus expressed as PO₄³⁻-P/total phosphorus (TP) (0.15 and 0.08 g/g, respectively) probably due to the lower pH obtained. All SFS produced enough soluble carbon, measured as VFAs, to stoichiometrically denitrify the nitrogen (N) contained in the faeces and potentially additionally 86–100% of all N produced from the fish culture process.     

Effect of extracellular-enzyme activities on solubilization rate of soil organic nitrogen

In a sandy soil containing ¹⁵N-labeled active (soluble and easily degradable) and non-labelled passive (recalcitrant) fractions of soil organic matter, the rate of net N mineralization (solubilization) was determined during a 55-day incubation at 25°C, 63% water-holding capacity and different levels of soil extracellular-enzyme activities. The active fraction of soil N was labelled by preincubation (at 5°C and 74% water-holding capacity for 6 months) of soil amended with ¹⁵N-labeled plant material. Increases in the activity of extracellular-enzymes in soil were induced by the addition of glucose and KH₂PO₄ at the beginning of the incubation. The results show that the contents of total soluble N (NO ₃ ^– –N+NH ₄ ⁺ –N + soluble organic N) were significantly higher in glucose-amended soil compared to the unamended soil. The increases in soluble N in soil amended with 1 and 2 mg glucose g^-1 dry soil corresponded to a mean rate of net solubilization of 7.9±1.4 and 18.8±0.7 nmol N g^-1 dry soil day^-1, respectively. The mean rate of net N solubilization (3.6±1.0 nmol N g^-1 dry soil day^-1) in unamended soil was significantly lower than those of glucose amended soils. The content of ¹⁵N in total soluble N in soil amended with 2 mg glucose, for example, was diluted from 3.11±0.08 atom% before the incubation to 2.77±0.03 atom% after 55 days. This indicates that 89% of soluble-N accumulated in soil by the end of the incubation originated from the active fraction of soil N and the rest, estimated at 11%, originated from the passive fraction. The activities of soluble and total proteases as well as the rate of N solubilization in the soil increased with the application of glucose. The activity of these extracellular enzymes was highly correlated with the rates of net N solubilization. Thus, increases in extracellular-enzyme activities in glucose-amended soils had a priming effect on the solubilization of ¹⁵N-labeled active and non-labeled passive fractions of soil organic N. It seems that the activity of extracellular-enzymes expressed in terms of total and soluble protease activities could be a rate-limiting factor in the processes of soil organic N solubilization.     

烷基糖苷对石油增溶作用及其影响因素研究

应用生物表面活性剂烷基糖苷在室温下对石油进行增溶,分别考察了溶液pH和无机盐浓度变化对石油溶解效果的影响,并通过正交实验验证确定最佳条件。结果表明,烷基糖苷溶液在浓度超过临界胶束浓度时,表现出明显的增溶特性,其质量增溶比约为0.013;溶液浓度、pH和无机盐浓度变化均能显著影响增溶作用。实验条件下得到烷基糖苷增溶石油的最佳条件为:烷基糖苷浓度39.00 g/L,pH为5,无机盐浓度0.5 mol/L,得到最大溶油量3.99 g/L。     

Solubilization of toxic metal minerals and metal tolerance of mycorrhizal fungi

This work investigates the ability of ericoid mycorrhizal (ErM) and ectomycorrhizal (EcM) fungi to solubilize different toxic metal (Cd, Cu, Pb, Zn)-containing minerals. Minerals were incorporated into solidified agar media and solubilization assessed by measuring clearing of the agar after fungal growth. Measurement of radial growth and biomass dry weight provided indications of metal tolerance: accumulated metal in the biomass was measured by atomic absorption spectrophotometry. Metal tolerance and solubilizing ability varied widely between different mineral and fungal species, and strains derived from sites of differing degrees of metal pollution. Zinc phosphate exhibited the least toxicity and was the easiest to solubilize by the majority of tested fungal isolates. Solubilization of toxic metal minerals was connected with both the pH of the medium and growth and tolerance of fungi and it seems that acidification of the medium was the main mechanism of mineral dissolution for most of the mycorrhizal fungi studied. A very strong lethal effect was observed for ectomycorrhizal isolates (>60% of strains) in the presence of Pb phosphate, carbonate, sulphide and tetraoxide. In contrast, ericoid mycorrhizal isolates were able to grow on Pb-mineral-amended media. A significant proportion of ericoid mycorrhizal cultures (70-90%) solubilized Cd and Cu phosphates and cuprite. None of the ericoid mycorrhizal and ectomycorrhizal fungi were able to produce a clear zone in Pb mineral-containing agar. However, many fungi were able to accumulate mobilized Pb in their mycelia. Differences in toxic metal mineral tolerance, mineral solubilization and metal uptake between populations isolated from metal-polluted and uncontaminated sites were related to the toxic metal which was the main pollutant in the original contaminated environment. In general, metal-tolerant fungi grew and solubilized toxic metal minerals better than non-tolerant isolates.     

Rock Phosphate Solubilization Mechanisms of One Fungus and One Bacterium

Many microorganisms can dissolve the insoluble phosphates like apatite. However, the mechanisms are still not clear. This study was an attempt to investigate the mechanisms of rock phosphate solubilization by an Aspergillus 2TCiF2 and an Arthrobacter1TCRi7. The results indicated that the fungus produced a large amount of organic acids, mainly oxalic acid. The total quantity of the organic acids produced by the fungus was 550 times higher than that by the bacterium. Different organic acids had completely different capacities to solubilize the rock. Oxalic acid and citric acid had stronger capacity to dissolve the rock than malic acid, tartaric acid, lactic acid, acetic acid, malonic acid and succinic acid. The fungus solubilized the rock through excreting both proton and organic acids. The rock solubilization of the bacterium depended on only proton.     

土壤固定态P的微生物转化和利用研究

本文综述了土壤中固定态P的存在方式及其微生物的转化和利用 .着重阐述细菌和真菌对土壤难溶性磷酸盐的解磷作用及其机理 ;同时也对热带—亚热带地区以可变电荷矿物为主的红黄壤中专性吸附磷的微生物转化和利用研究作了概述     

改性水溶性羧甲基壳聚糖对铅的解吸行为研究

[目的]研究改性的水溶性羧甲基壳聚糖(WSCC)对铅的增溶、解吸行为.[方法]研究WSCC对铅的增溶作用,并利用WSCC进行铅污染土壤的解吸试验,考察了pH、离子强度、有机质和WSCC初始浓度对铅的解吸影响.[结果]WSCC对碳酸铅的增溶效果显著,当其浓度为2 g/L时,水溶液中Pb2+浓度可达到600 mg/L.WSCC对铅解吸能力随着土壤中有机质含量的增加而降低,pH的升高、离子强度的增加和WSCC初始浓度增加有利于铅的解吸.[结论]该静态解吸研究可为铅污染土壤的修复提供基础信息及依据.     

不同平均取代度的甲基化-β-环糊精对泰乐菌素的增溶作用

[目的]探讨甲基化-β-环糊精对泰乐菌素的增溶作用。[方法]采用相溶解图法,研究不同取代度的绿色甲基化-β-环糊精对药物泰乐菌素的增溶作用,并测定包合稳定常数和增溶效果。[结果]泰乐菌素与甲基化-β-环糊精以1∶1的包结比形成包结物。β-环糊精与不同平均取代度的甲基化-β-环糊精对泰乐菌素均有增溶作用,平均取代度为14.2的甲基化-β-环糊精对泰乐菌素的增溶作用最为显著,增溶倍数为1.5。[结论]该研究可为泰乐菌素的临床应用提供参考。