Jong-Kang Liu

Enzymatic degradation of nitriles by Klebsiella oxytoca.

Klebsiella oxytoca, isolated from cyanide-containing wastewater, was able to utilize many nitriles as sole source of nitrogen. The major objective of this study was to explore the ability of K. oxytoca to utilize some nitriles and then further evaluate the pathways of transformation of cyanide compounds by K. oxytoca. Results from this study indicate that succinonitrile and valeronitrile were the most optimal sources of nitrogen for the growth of K. oxytoca. The biodegradation of acetonitrile proceeded with the formation of acetamide followed by acetic acid. The production of ammonia was also detected in this biodegradation experiment. Similar results were observed in the propionitrile biodegradation experiments. Collectively, this study suggests that the breakdown of acetonitrile or propionitrile by this bacterium was via a two-step enzymatic hydrolysis with amides as the intermediates and organic acids plus with ammonia as the end products.

Promising antimicrobial capability of thin film metallic glasses

Thin film metallic glasses (TFMGs) are demonstrated to exhibit excellent surface flatness, high corrosion resistance and satisfactory hydrophobic properties. Moreover, the antimicrobial and biocompatibility abilities of TFMGs are examined and the results are compared with the behavior of pure Ag and 316L stainless steel. Three TFMGs, Al48Ag37Ti15, Zr54Ti35Si11, and Zr59Ti22Ag19, are prepared by sputtering to assess the antimicrobial performance against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, which are the most common nosocomial infection pathogens. Experimental results show that the antimicrobial effect of the Al- or Ag-containing AlAgTi and ZrTiAg TFMGs is similar to that of the pure Ag coating. The ZrTiSi TFMG with no Ag or Al shows poor antimicrobial capability. The physical properties of highly smooth surface and hydrophobic nature alone are not sufficient to result in promising antimicrobial ability. The chemical metal ion release still plays a major role, which should be born in mind in designing biomedical devices.

Application of polycolloid-releasing substrate to remediate trichloroethylene-contaminated groundwater: a pilot-scale study.

The objectives of this pilot-scale study were to (1) evaluate the effectiveness of bioremediation of trichloroethylene (TCE)-contaminated groundwater with the supplement of slow polycolloid-releasing substrate (SPRS) (contained vegetable oil, cane molasses, surfactants) under reductive dechlorinating conditions, (2) apply gene analyses to confirm the existence of TCE-dechlorinating genes, and (3) apply the real-time polymerase chain reaction (PCR) to evaluate the variations in TCE-dechlorinating bacteria (Dehalococcoides spp.). Approximately 350L of SPRS solution was supplied into an injection well (IW) and groundwater samples were collected and analyzed from IW and monitor wells periodically. Results show that the SPRS caused a rapid increase of the total organic carbon concentration (up to 5794mg/L), and reductive dechlorination of TCE was significantly enhanced. TCE dechlorination byproducts were observed and up to 99% of TCE removal (initial TCE concentration=1872μg/L) was observed after 50 days of operation. The population of Dehalococcoides spp. increased from 4.6×10(1) to 3.41×10(7)cells/L after 20 days of operation. DNA sequencing results show that there were 31 bacterial species verified, which might be related to TCE biodegradation. Results demonstrate that the microbial analysis and real-time PCR are useful tools to evaluate the effectiveness of TCE reductive dechlorination.

Clean up of petroleum-hydrocarbon contaminated soils using enhanced bioremediation system: laboratory feasibility study.

The objective of this study was to assess the potential of applying enhanced bioremediation on the treatment of petroleum-hydrocarbon contaminated soils. Microcosm experiments were conducted to determine the optimal biodegradation conditions. The control factors included oxygen content, nutrient addition, addition of commercially available mixed microbial inocula, addition of wood chip and rice husk mixtures (volume ratio=1:1 ) as bulking agents, and addition of organic amendments (chicken manures). Results indicate that the supplement of microbial inocula or chicken manures could significantly increase the microbial populations in soils, and thus enhance the efficiency of total petroleum hydrocarbon (TPH) removal (initial TPH=5,500 mg/kg ). The highest first-order TPH decay rate and removal ratio were approximately 0.015  day−1 and 85%, respectively, observed in microcosms containing microbial inocula (mass ratio of soil to inocula=50:1 ), nutrient, and bulking agent (volume ratio of soil to bulking agen...

Use of specific gene analysis to assess the effectiveness of surfactant-enhanced trichloroethylene cometabolism.

The objective of this study was to evaluate the effectiveness of in situ bioremediation of trichloroethylene (TCE)-contaminated groundwater using specific gene analyses under the following conditions: (1) pretreatment with biodegradable surfactants [Simple Green™ (SG) and soya lecithin (SL)] to enhance TCE desorption and dissolution, and (2) supplementation with SG, SL, and cane molasses as primary substrates to enhance the aerobic cometabolism of TCE. Polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), and nucleotide sequence analysis were applied to monitor the variations in specific activity-dependent enzymes and dominant microorganisms. Results show that TCE-degrading enzymes, including toluene monooxygenase, toluene dioxygenase, and phenol monooxygenase, were identified from sediment samples collected from a TCE-spill site. Results from the microcosm study show that addition of SG, SL, or cane molasses can enhance the aerobic cometabolism of TCE. The TCE degradation rates were highest in microcosms with added SL, the second highest in microcosms containing SG, and lowest in microcosms containing cane molasses. This indicates that SG and SL can serve as TCE dissolution agents and act as primary substrates for indigenous microorganisms. Four dominant microorganisms (Rhodobacter sp., Methyloversatilis sp., Beta proteobacterium sp., and Hydrogenophaga pseudoflava) observed in microcosms might be able to produce TCE-degrading enzymes for TCE cometabolic processes.

Enhanced anaerobic biodegradation of OCDD-contaminated soils by Pseudomonas mendocina NSYSU: microcosm, pilot-scale, and gene studies.

In this study, microcosm and pilot-scale experiments were performed to investigate the capability and effectiveness of Pseudomonas mendocina NSYSU (P. mendocina NSYSU) on the bioremediation of octachlorodibenzo-p-dioxin (OCDD)-contaminated soils. The objectives were to evaluate the (1) characteristics of P. mendocina NSYSU, (2) feasibility of enhancing OCDD biodegradation with the addition of P. mendocina NSYSU and lecithin, and (3) variation in microbial diversity and genes responsible for the dechlorination of OCDD. P. mendocina NSYSU was inhibited when salinity was higher than 7%, and it could biodegrade OCDD under reductive dechlorinating conditions. Lecithin could serve as the solubilization agent causing the enhanced solubilization and dechlorination of OCDD. Up to 71 and 62% of OCDD could be degraded after 65 days of incubation under anaerobic conditions with and without the addition of lecithin, respectively. Decreased OCDD concentrations caused significant increase in microbial diversity. Results from the pilot-scale study show that up to 75% of OCDD could be degraded after a 2.5-month operational period with lecithin addition. Results from the gene analyses show that two genes encoding the extradiol/intradiol ring-cleavage dioxygenase and five genes encoding the hydrolase in P. mendocina NSYSU were identified and played important roles in OCDD degradation.

Evaluation of Enhanced Reductive Dechlorination of Trichloroethylene Using Gene Analysis: Pilot-Scale Study

AbstractThe industrial solvent trichloroethylene (TCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this pilot-scale study was to evaluate the effectiveness of an in situ reductive dechlorination process to remediate TCE-contaminated groundwater at a TCE-spill site using specific gene analysis. An injection well was installed inside the TCE plume for substrate and inocula injection. Brown sugar and anaerobic activated sludge (collected from an industrial wastewater-treatment plant with influent containing TCE) as electron donor (primary substrate) and inocula, respectively, were injected to enhance the TCE biodegradation rate through anaerobic reductive dechlorination. Three monitor wells were installed downgradient of the injection well along the groundwater flow path to monitor the TCE degradation trend. Polymerase chain reaction (PCR) analytical results reveal that the major TCE degrader (Dehalococcoides) and TCE-degrading genes (vcrA and tceA)...

Expression of cerebral serotonin related to anxiety-like behaviors in C57BL/6 offspring induced by repeated subcutaneous prenatal exposure to low-dose lipopolysaccharide

Prenatal exposure to lipopolysaccharide (LPS), which likely occurs due to infection or contact with environmental allergens during pregnancy, is a proposed risk factor that induces anxiety- and autism spectrum disorder-like behaviors in offspring. However, the molecular and behavioral changes in offspring after maternal immune activation have not been completely identified. We hypothesized that a subcutaneous injection of LPS in a pregnant mouse would induce changes in cerebral serotonin (5-HT) in parallel to the appearance of anxiety-like behaviors in the dam’s offspring. After LPS injections (total, 100 μg/Kg), the time spent in the central region during the open field test and the number of times that the mice moved between the light and dark boxes and between the open and closed arms on the elevated plus maze test revealed anxiety-like behaviors in offspring at 5, 6 and 9 weeks of age. The mRNA expression levels of tph2 (5-HT synthesizing enzyme) and slc6a4 (5-HT transporter) were down-regulated in both adolescent (5 weeks of age) and adult (8 weeks of age) brains. Immunohistochemistry revealed that the numbers and sizes of tph2-expressing cells were notably decreased in the raphe nuclei of the midbrain of adults. Moreover, compared with controls (phosphate-buffered saline-treated offspring), the cerebral 5-HT concentration at adolescence and adulthood in LPS-induced offspring was significantly decreased. We concluded that maternal immune activation induced by exposure to a low dose of LPS decreased cerebral 5-HT levels in parallel to the down-regulation of the tph2 and slc6a4 genes and in conjunction with anxiety-like behaviors in offspring.

A comparison of the immunological potency of Burkholderia lipopolysaccharides in endotoxemic BALB/c mice

Lipopolysaccharide is one of the virulence factors of the soil‐borne pathogens Burkholderia pseudomallei, B. thailandensis, B. cenocepacia and B. multivorans, which cause septic melioidosis (often in B. pseudomallei infections but rarely in B. thailandensis infections) or cepacia syndromes (commonly in B. cenocepacia infections but rarely in B. multivorans infections). The inflammatory responses in Burkholderia LPS‐induced endotoxemia were evaluated in this study. Prior to induction, the conserved structures and functions of each purified LPS were determined using electrophoretic phenotypes, the ratios of 3‐hydroxytetradecanoic to 3‐hydroxyhexadecanoic acid and endotoxin units. In an in vitro assay, cytokine expression of myeloid differentiation primary response gene 88 and Toll/IL‐1 receptor domain containing adapter‐inducing INF‐β‐dependent signaling‐dependent signaling differed when stimulated by different LPS. Endotoxemia was induced in mice by s.c. injection as evidenced by increasing serum concentrations of 3‐hydroxytetradecanoic acid and the septic prognostic markers CD62E and ICAM‐1. During endotoxemia, splenic CD11b+I‐A+, CD11b+CD80+, CD11b+CD86+ and CD11b+CD11c+ subpopulations increased. After induction with B. pseudomallei LPS, there were significant increases in splenic CD49b NK cells and CD14 macrophages. The inflamed CD11b+CCR2+, CD11b+CD31+, CD11b+CD14+, resident CD11b+CX3CR1+ and progenitor CD11b+CD34+ cells showed delayed increases in bone marrow. B. multivorans LPS was the most potent inducer of serum cytokines and chemokines, whereas B. cenocepacia LPS induced relatively low concentrations of the chemokines MIP‐1α and MIP‐1β. Endotoxin activities did not correlate with the virulence of Burkholderia strains. Thus factors other than LPS and/or other mechanisms of low activity LPS must mediate the pathogenicity of highly virulent Burkholderia strains.

Genomic Sequence of Burkholderia multivorans NKI379, a Soil Bacterium That Inhibits the Growth of Burkholderia pseudomallei.

ABSTRACT Burkholderia multivorans NKI379 is a soil bacterium that exhibits an antagonistic effect against the growth of Burkholderia pseudomallei, the causative agent of the infectious disease melioidosis. We report the draft genomic sequence of B. multivorans NKI379, which has a G+C content of 67% and 5,203 candidate protein-encoding genes.