耐低pH氧化亚铁硫杆菌的培养与驯化

采用9K培养基从沙洲坝铀矿石中分离出一株耐低pH(pH=1.6)的氧化亚铁硫杆菌(B16),经多次驯化,它可以适应矿石培养基和矿石酸化液。从而证实,用矿石酸化液替代9K培养基培养氧化亚铁硫杆菌是可行的。     

耐高矿化度浸矿菌的驯化及浸铀效果

从721铀矿石样中分离出的一株氧化亚铁钩端螺旋菌(Leptospirillums ferrooxidans)与氧化亚铁硫杆菌(Thiobacillus ferrooxidans)的混合菌株,经不同条件的驯化及紫外线诱变处理后,可在高矿化度(M>50g/L)、低pH(pH=1.4)的铀矿石酸化液中良好生长。实验室槽浸实验表明,这一混合菌株对低pH、高矿化度的浸出体系具有良好的适应性,仅用7天时间,渣计浸出率达90.06%,浸出过程中未出现铁损失。     

微波加热预处理堆浸铀矿石

为了考察微波功率、辐射时间和物料质量对铀矿石浸出率和浸出周期的影响,采用频率为2.45 GHz微波对花岗岩铀矿石进行加热,然后配置了不同预处理条件下的铀矿样进行室内柱浸试验,并分析了不同微波功率预处理时铀矿石比表面积和孔隙率的变化。研究结果表明:微波预处理的温度应控制在600℃以下。当微波功率为40 k W,辐射时间为40 s,矿石质量为4 kg时,铀浸出率为85.27%,浸出周期为67 d,较原矿浸出率提高7.69%,浸出周期缩短25 d。4 kg矿石经40 k W微波辐射120 s后,比表面积较原矿增大39.9%,孔隙率增加71.8%。利用扫描电镜(SEM)观察微波预处理前后表面形貌,预处理后原有微裂隙扩展并加深,并出现新的裂缝。微波预处理改善了铀矿石渗透性,有利于浸出。     

酸度及酸化介质对铀矿石微生物浸出酸化的影响

通过室内柱浸试验,研究了溶浸液加入硫酸的浓度和酸化介质类型对铀矿石生物浸出酸化阶段的影响。结果表明,当初始硫酸浓度相同时,尾液比清水酸化时间短、耗酸率低,两者浸铀率相差不大,尾液比清水的累计净铁浸出量小,但后期差值逐渐缩小。尾液介质酸化时,随着初始酸度的增大,酸化时间缩短,累计净铁浸出量增加,但耗酸率增高,累计铀浸出率增大。合适的方案为酸化阶段采用尾液介质、40g/L初始硫酸浓度酸化。     

铀矿石不同酸度下细菌的溶浸试验

对某铀矿石在不同酸度下细菌溶浸浸铀进行了对比试验,分析了浸出过程中铀浸出率、酸耗和细菌生长等变化规律。结果表明,该铀矿石不同酸度下细菌溶浸效果较好,液计平均浸出率为87.7%,渣计平均浸出率为94.1%;另外,在酸化阶段,硫酸浓度对浸出总耗酸影响不大,但浓酸可以大幅度缩短酸化时间;在细菌浸出阶段,pH越高耗酸越低,细菌生长情况越好,但铀浸出率并未随之增高,主要是因为较高pH的浸出液中容易产生铁的氢氧化物和铁矾沉淀,阻止了铀的进一步浸出。     

沥青铀矿石硫酸和细菌浸出过程的比较研究

以沥青铀矿石为对象,进行了10g/L、20g/L硫酸浸出和上述两种条件酸化后的细菌浸出试验。结果表明,上述四种条件下铀浸出率分别为20.86%、26.47%、30.29%和35.53%,细菌可以有效氧化浸出体系中的元素硫和Fe2+,使pH、Eh、亚铁离子浓度、总铁浓度等特征参数朝着有利于铀矿石浸出的方向变化;在同等条件下,细菌浸出的浸出率比硫酸浸出的提高了34.8%～45.2%。     

微生物浸出稀有金属矿石

微生物湿法冶金技术已在低品位铜、铀矿石的浸出和难处理金矿的氧化脱砷预处理等方面应用,研究范围正在扩大。本文就微生物浸出矿石的特征以及在稀有金属矿石的微生物浸出方面的研究情况进行了讨论。     

不同产状铀矿石的浸出特性

本实验研究了自前寒武纪到第四纪地层中赋存的几种铀矿石的浸出性能。对这几种铀矿石的各自适宜的浸出方法及其浸出条件进行了实验。结果表明,沉积岩型矿床的矿石铀浸出性能比火成岩矿床的矿石铀浸出性能好得多,还表明,生成地质时代近的铀矿石比生成年代远的铀矿石容易浸出。     

难浸铀矿石微生物浸铀试验

对我国南方某硬岩难浸铀矿石分别开展了不同酸耗、矿浆液固比、不同初始铁浓度摇瓶搅拌浸出试验,考察铀浸出率(浓度)与酸浓度、菌液三价铁浓度、液固比和Eh之间的关系。最佳工艺参数为:酸化酸度30~60g/L、酸耗8%~15%、液固比(2.5~5.0)∶1、三价铁浓度5~7g/L。     

用嗜酸氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans)从硅酸盐-磷灰石矿石中溶解铀

Abhilash S．Singh等研究了印度低品位硅酸盐-磷灰石铀矿石的生物浸出。矿石中含0．024％U3O8和10．6％铁及少量贱金属。用采自矿山的用于产生氧化剂铁离子的富含嗜酸氧化亚铁硫杆菌（Acidithiobacillus ferrooxidans（A.ferrooxidans））的菌液提取铀。     

微生物在土壤中迁移实验与数值模拟

A thorough understanding of bacteria transport in soil and groundwater is vital to the successful practice of environmental bioremediation. In this work, a dual-process adsorption with growth and decay model of bacterial transport was proposed. The on-site soil and the high efficiency methyl tert-butyl ether (MTBE) degrading bacterium Chryseobacterium sp.A-3, was used in the experiments. The model was validated using one-dimensional soil column experiments. The results show that the dual-process adsorption with growth and decay model proposed well describes the migration mechanism of microorganisms in soil and groundwater environment. According to the model analysis and simulation, the bacterial transport is enhanced as flow velocity and inlet cell concentration increase. Compared with the contaminant MTBE, the bacteria show stronger transport capacity but the irreversible straining in soil prevents the bacteria from transporting longer than MTBE. The results have certain instructive significance to the in-situ contamination remediation operation.     

难处理金矿预氧化高效嗜热菌的选育研究

采集南方某煤矿酸性矿坑水并从中选育分离出一株中等嗜热菌;利用分子生物学鉴定方法确定其为Sulfobacillus属,典型种为Sul-fobacillusthermosulfidooxidans。将该菌株应用于黄铁矿单体矿物的氧化,通过扫描电镜观察发现,黄铁矿浸出前颗粒完整、结构致密,经预氧化后,结构疏松,形成空洞和裂纹,黄铁矿致密结构被破坏;经过16d生物预氧化,单体黄铁矿被氧化60%以上,达到暴露单体金的目的。试验结果表明该菌株是一株活性较高的高效嗜热浸矿功能菌。     

Growth hormone treatment of children with neural tube defects: results from 6 months to 6 years

OBJECTIVE: Patients with neural tube defects (myelomeningocele) have severe growth retardation, and treatment with recombinant human growth hormone (rHGH) for 6 months accelerates growth velocity. We examined patients treated for longer periods to determine whether accelerated growth persists, and whether patients demonstrated to be growth hormone deficient have a greater response to rHGH therapy. METHODS: We retrospectively evaluated the growth rate and length standard deviation score (SDS) of 22 patients in response to treatment with 0.3 mg/kg per week of rHGH for 7 to 72 months. Nine of 22 patients were growth hormone deficient (nocturnal and provocative growth hormone responses < 7 ng/ml). Treatment success was defined as an increase of length SDS of > 0.2 SD per year. RESULTS: Fourteen patients (64%) had treatment successes, and eight had treatment failures. Length SDS improved from a pretreatment value of -2.9 (+/- 1.2) to the most recent length SDS of -1.9 (+/- 1.4) (p < 0.001). The growth rate was significantly increased through year 4 of treatment. The annualized growth rate after 6 months of rHGH treatment was significantly different for the success and failure groups (11.0 +/- 2.6 cm/yr vs 5.1 +/- 3 cm/yr, p < 0.001). The annualized 6-month growth rate during treatment was related to the probability of treatment success. CONCLUSION: Treatment with rHGH significantly improves the growth rate and length SDS of children with neural tube defects. The 6-month annualized growth velocity during treatment was predictive of long-term treatment response. The effect on adult stature is unknown.     

Antimicrobial actions of fluoride for oral bacteria

Fluoride is widely used as a highly effective anticaries agent. Although it is felt that its anticaries action is related mainly to effects on mineral phases of teeth and on the process of remineralization, fluoride also has important effects on the bacteria of dental plaque, which are responsible for the acidification of plaque that results in demineralization. The results of recent studies have shown that fluoride can affect bacterial metabolism through a set of actions with fundamentally different mechanisms. It can act directly as an enzyme inhibitor, for example for the glycolytic enzyme enolase, which is inhibited in a quasi-irreversible manner. Direct action seems also to occur in inhibition of heme-based peroxidases with binding of fluoride to heme. The flavin-based peroxidases of many oral bacteria are insensitive to fluoride. Another mode of action involves formation of metal-fluoride complexes, most commonly AlF4-. These complexes are responsible for fluoride inhibition of proton-translocating F-ATPases and are thought to act by mimicking phosphate to form complexes with ADP at reaction centers of the enzymes. However, the actions of fluoride that are most pertinent to reducing the cariogenicity of dental plaque are those related to its weak-acid character. Fluoride acts to enhance membrane permeabilities to protons and compromises the functioning of F-ATPases in exporting protons, thereby inducing cytoplasmic acidification and acid inhibition of glycolytic enzymes. Basically, fluoride acts to reduce the acid tolerance of the bacteria. It is most effective at acid pH values. In the acidic conditions of cariogenic plaque, fluoride at levels as low as 0.1 mM can cause complete arrest of glycolysis by intact cells of Streptococcus mutans. Overall, the anticaries actions of fluoride appear to be complex, involving effects both on bacteria and on mineral phases. The antibacterial actions of fluoride appear themselves to be complex but to be dominated by weak-acid effects.     

Effects of dietary biotin on enhanced sucrose intake and enhanced gustatory nerve responses to sucrose seen in diabetic OLETF rat

Vicilin (7S storage proteins) isolated from different legume seeds were shown to inhibit yeast growth and glucose stimulated acidification of the medium by yeast cells. The degree of growth inhibition varied with the origin of vicilins. It was more than 90% for vicilins from cowpea (Vigna unguiculata, cultivar pitiuba) and equal to 65% for vicilins from Vigna radiata, in the case of Saccharomyces cerevisae. Vicilins from cowpea seeds inhibited the glucose stimulated acidification of the medium by S. cerevisae up to 60%. We have also observed that vicilins bind to yeast cells. We suggest that vicilins bind to chitin-containing structures of yeast cells and that such association could result in inhibition of H+ pumping, cell growth and spore formation. A final consequence of the yeast growth inhibition by vicilins is (probably) the formation of spores.     

Growth stimulation of sulfur oxidizing bacteria for optimization of metal leaching efficiency of fly ash from municipal solid waste incineration

Sulfur oxidizing bacteria were used to leach metals bound in municipal solid waste incineration fly ash. Pure or mixed cultures of Thiobacilli with or without addition of anoxic sewage sludge were incubated with various amounts of fly ash for several weeks. Co-cultures with Thiobacilli and sewage sludge grew faster than pure cultures of T. thiooxidans or cultures with only sewage sludge as inoculum. The addition of sewage sludge increased the rate of growth of sulfur oxidizing bacteria and simultaneously enhanced the acidification of the suspension. As a result, the time for fly ash processing was reduced by 50%. Thiobacilli were able to grow in the presence of up to 8% (w/v) fly ash. Depending on the amounts of fly ash added, the final pH, and the concentration of sulfuric acid formed, different amounts of metals were leached: over 80% for Cd, Cu, and Zn, 60% for Al and approx. 30% for Fe and Ni (totally, approx. 50% of the heavy metals present in the fly ash) were extracted.     

某铀矿生物浸铀过程中金属离子与铀协同浸出研究

通过室内柱浸试验,探析不同粒度（2.5~5、5~10、2.5~10 mm）铀矿在生物浸出过程中金属离子与铀浸出的规律,分析柱浸过程中pH、Eh、K+、Ca2+、Na+、Mg2+、Al3+、Fe3+与铀的浸出行为,并运用PHREEQC计算金属离子的饱和指数及浸出液中铀的存在形式。结果表明,铀矿中K+、Ca2+、Na+、Mg2+、Al3+、Fe3+与铀的浸出趋势相似,粒度越小该铀矿中浸出的金属离子越多,经过66 d柱浸试验,三种粒度的铀矿铀浸出率分别为85.93%、69.75%、79.65%。酸化阶段及菌浸阶段硬石膏达到饱和,酸化阶段磷酸铀酰达到饱和,菌浸阶段氟化铁达到饱和。柱浸浸出液中铀主要以正六价存在,酸化阶段铀化学形态主要为硫酸铀酰及磷酸铀酰,菌浸出阶段主要为硫酸铀酰及氟化铀酰。     

生物氧化预处理工艺控制系统研究与应用

通过对生物氧化预处理工艺中所选用菌种及主要参数的研究,得出生物氧化预处理控制系统中的优化工艺参数组合,并在实际生产过程中得以应用,取得良好的控制效果,提金率得到了明显的提高,为稳定生产提供了技术保障.     

Effect of oxytetracycline-medicated feed on antibiotic resistance of gram-negative bacteria in catfish ponds

The effect of oxytetracycline-medicated feeds on antibiotic resistance in gram-negative bacteria from fish intestines and water in catfish ponds was investigated. In experiments in the fall and spring, using ponds with no previous history of antibiotic usage, percentages of tetracycline-resistant bacteria in catfish intestines obtained from medicated ponds increased significantly after 10 days of treatment. In the fall, resistance of the intestinal and aquatic bacteria returned to pretreatment levels within 21 days after treatment. In the spring, resistance declined after treatment but remained higher than pretreatment levels for at least 21 days in intestinal bacteria and for 5 months in aquatic bacteria. Plesiomonas shigelloides, Aeromonas hydrophila, and Citrobacter freundii were isolated frequently in both spring and fall; Escherichia coli, Klebsiella pneumoniae, Edwardsiella tarda, and Enterobacter spp. were isolated primarily in the spring. Oxytetracycline treatment did not affect the distribution of bacterial species in the fall but may have accelerated a shift toward greater prevalence of members of the family Enterobacteriaceae in the spring. Multiple antibiotic resistance did not appear to be elicited by oxytetracycline treatment.