The detoxification potential of ferric ions for bioleaching of the chalcopyrite associated with fluoride-bearing gangue mineral.

Fluoride toxicity to microorganisms was a predominant factor contributing to the failure of a commercial scale bioleach heap. An integrated control strategy for fluoride complexation without jarosite generation by stepwise adding ferric ions was first proposed to enable the bioleaching of the chalcopyrite associated with fluoride-bearing gangue mineral by Acidithiobacillus ferrooxidans. Chemical speciation calculation revealed that with the presence of Fe3+, the concentration of the main lethal fluoride to microorganism, HF, decreased dramatically. The pure culture study showed that the detrimental effect of fluoride on microorganism was eliminated by increasing the molar ratio of Fe3+/F- to 3:1. Furthermore, chalcopyrite bioleaching experiment revealed the minimum Fe3+/F- molar ratio that enabled the bioleaching was 6:1. Stepwise addition was an effective way to promote a balanced system and avoid the formation of jarosite caused by the excessive Fe3+. Above all, the introduction of Fe3+ is a feasible method for reducing the fluoride toxicity during the bioleaching of chalcopyrite, shedding light on the industrial applications.

Effective bioleaching of low-grade copper ores: Insights from microbial cross experiments.

The interaction between microorganisms and minerals was a hot topic to reveal the transformation of key elements that affecting bioleaching efficiency. Three typical low-grade copper ores, the main copper-bearing components of which were primary sulfide, secondary sulfide and high-oxidative sulfide copper, were obtained from Dexing, Zijinshan and Luanshya copper mine, respectively. Meanwhile, six typical microorganisms were isolated from each of the three habitats, and assembled as communities based on their origins. Cross bioleaching was carried out under identical conditions. The leaching parameters showed that native strains played excellent roles in their corresponding ore bioleaching process, and community structure was greatly determined by mineral composition, indicating that domestication for longitudinal adaption was an effective way to improve microbial leaching performance. Leptospirillum ferriphilum and Acidithiobacillus ferrooxidans promoted copper release by shifting redox potential and pH of the leachate, respectively, indicating that microbial population regulation was another effective way to improve bioleaching efficiency.

Metatranscriptomics reveals microbial adaptation and resistance to extreme environment coupling with bioleaching performance.

Chalcopyrite bioleaching by 2, 4 and 6 acidophilic strains with the same inoculation density were studied, respectively. The results indicated that the 6-strain community firstly adapted to bioleaching environment, dissolved the chalcopyrite rapidly and maintained an efficient work until late stage. Transcriptome profiles of the 6-strain community at 6th and 30th day during bioleaching process were investigated by RNA-seq. Comparative transcriptomics identified 226 and 737 significantly up-regulated genes at early and late stage, respectively. Gene annotation results revealed that microorganisms adapted to the oligotrophic environment by enhancing cell proliferation, catalytic activation and binding action to maintain their life activities at early stage, and genes related to signal transduction, localization and transporter were highly expressed as an effective response to the stressful late stage. A graphical representation was presented to show how microorganisms adapted and resisted to the extreme environment by their inner functional properties and promoted the bioleaching efficiency.

[Population pharmacokinetics of phenytoin in pediatric patients].

OBJECTIVE: To study population pharmacokinetics of phenytoin in pediatric patients by using sparse data. METHODS: We used routinely collected therapeutic drug monitoring data, derived from the steady state serum concentrations of phenytoin in 42 pediatric outpatients with epilepsy. Depending on whether the patients were administered with phenytoin alone or coadministered with phenobabital or clonazepam, the subjects were divided into two groups: phenytoin group and coadministration group. The population parameter and individual parameter of phenytoin in children were estimated using Monte Carlo method. RESULTS: The children's phenytoin population pharmacokinetic parameters Vm and Km were 9.8 mg.kg(-1).d(-1) and 2.73 mg/L in phenytoin group; and 9.2 mg.kg(-1).d(-1) and 3.24 mg/L in coadministration group. There were good relationship between predicted and determined concentrations with correlation coefficient of 0.999 and 0.984, respectively. CONCLUSION: The coadministration of phenobarbital or clonazepam obviously affected the pharmacokinetics of phenytoin. The population pharmacokinetics of phenytoin in children may provide a usefull index for individualization of dosage regimen.