Biomedical subjects

H H Fang

Publications and source records attributed to H H Fang.

16 recordsLinked to original sources

PubMed2001

Phylogenetic diversity of a SRB-rich marine biofilm.

This study was conducted to characterize the phylogenetic diversity of a corrosive marine biofilm based on 16S rDNA. Results of phylogenetic analysis indicated that, out of the 112 clones developed, 52 clones (46.4%) were affiliated with two families of sulfate-reducing bacteria: Desulfovibrionaceae and Desulfobacteriaceae. Another 44 clones (39.3%) were affiliated with the Clostridiaceae family of low G+C, gram-positive bacteria. Three clones (2.7%) were closely related to Chlorobium vibrioforme, a green sulfur bacterium.

Base Sequence↗

PubMed2001

The roles of calcium in sludge granulation during UASB reactor start-up.

Six upflow anaerobic sludge blanket (UASB) reactors were concurrently operated for 146 d to examine the effects of calcium on the sludge granulation process during start-up. Introduction of Ca2+ at concentrations from 150 to 300 mg/l enhanced the biomass accumulation and granulation process. The calcium concentration in the granules was nearly proportional to the calcium concentration in the feed, and calcium carbonate was the main calcium precipitate in the granules. The specific activity of granules decreased with increasing influent calcium concentration. The optimum calcium concentration for the granulation was from 150 to 300 mg/l. The addition of low-concentration calcium to the UASB reactors appeared to enhance the three steps of sludge granulation: adsorption, adhesion and multiplication, but it did not lead to a different proliferation of predominant microorganisms in the granules.

Anaerobiosis↗

PubMed2001

Acidification of mid- and high-strength dairy wastewaters.

Batch and continuous experiments were conducted to study the influence of dairy wastewater strength (2-30g-COD/L) on acidification at pH 5.5 and 37 degrees C. Results of batch experiments showed that carbohydrate was preferentially acidified as compared to protein and lipid. Production of VFAs (mainly acetate, propionate and butyrate) and hydrogen corresponded to carbohydrate acidification, whereas production of alcohols (mainly ethanol, propanol and butanol), plus i-butyrate and higher molecular-weight VFAs, corresponded to protein acidification. In treating high-strength wastewaters (8-30 g-COD/ L), acetate, butyrate and P(H2) decreased after reaching their peak levels before leveling off. Results of continuous experiments with 12h of hydraulic retention showed that acidification decreased with the increase of wastewater COD, from 57.1% at 2 g-COD/L to 28.8% at 30 g-COD/L; among the constituents in dairy wastewater, 92-99% of carbohydrates, 59-85% of protein and 12-42% of lipid were acidified. High-strength wastewater favored production of hydrogen and alcohols, especially propanol and butanol. The biomass yield was 0.258g-VSS/g-COD.

Agriculture↗

PubMed2001

Enhanced sludge granulation in upflow anaerobic sludge blanket (UASB) reactors by aluminum chloride.

Two upflow anaerobic sludge blanket (UASB) reactors were concurrently operated for 146 days to examine the effects of aluminum chloride (AlCl3) on the sludge granulation process during start-up. Sludge granulation (defined as that over 10% of granules were larger than 2.0 mm) was achieved in the control reactor (R1) in approximate three months. Introduction of Al3+ at a concentration of 300 mg/l reduced the sludge granulation time by approximate one month. Throughout the experiment the AlCl3-added reactor (R2) had a higher biomass concentration, e.g., 13.8 g-MLVSS/l versus 12.8 g-MLVSS/l on Day 146. Granules became visible earlier in R2 compared with R1 (35 days versus 65 days). The average size of granules from R2 was larger than that from R1. The results demonstrated that AlCl3 enhanced the sludge granulation process in the UASB reactors.

Aluminum Chloride↗

PubMed2001

Electrochemical oxidation of leachate pretreated in an upflow anaerobic sludge blanket reactor.

This study was conducted to develop a two-stage process for the treatment of Hong Kong leachate. The leachate, containing 4750 mg l-1 of chemical oxygen demand (COD) and 1310 mg l-1 of ammoniacal nitrogen (NH3-N), was first treated in a UASB (upflow anaerobic sludge blanket) reactor at 37 degrees C. The process removed on average 66.1% of COD with 6.1 days of hydraulic retention time (HRT), corresponding to an organic loading rate of 0.78 g-COD (l.day)-1. The UASB effluent, which had an average pH of 8.9, COD of 1610 mg l-1 and NH3-N of 1480 mg l-1, was then further treated by electrochemical oxidation in a batch reactor with recirculation. With the addition of 2000 mg l-1 of chloride (in the form of sodium chloride) and at a current density of 32.3 mA cm-2, 87% of COD and 100% of NH3-N were removed from the UASB effluent in six hours. The energy consumption was < 55 kWh kg-COD-1. The final effluent contained no residual NH3-N and only 209 mg l-1 of COD.

Electrochemistry↗

PubMed2001

Study of microbial community of brewery-treating granular sludge by denaturing gradient gel electrophoresis of 16S rRNA gene.

The microbial community structure of granular sludge from an upflow anaerobic sludge blanket (UASB) reactor treating brewery effluent was studied by denaturing gradient gel electrophoresis (DGGE). Twelve major bands were observed in the DGGE fingerprint for the Bacteria domain and four bands for the Archaea domain. Of the bacterial bands observed, six were successfully purified and sequenced. Among them, three were related to the gram-positive low G + C group, one to the Delta subclass of the Proteobacteria, one to the Gamma subclass, and one to the Cytophaga group with no close related sequence. The 16S rRNA sequences of the four archaeal bands were closely associated with Methanosaeta concilii and Methanobacterium formicum.

Bacteria, Anaerobic↗

PubMed2001

Adsorption of heavy metals by EPS of activated sludge.

Extracellular polymeric substances (EPSs) were extracted by high-speed centrifugation at 20,000 G for 30 min from an activated sludge treating municipal wastewater. Each gram of sludge, as measured in volatile suspended solids (VSS), contained 7.3 mg of EPS, including 6.5 mg of protein (EPSp) and 0.8 mg of carbohydrate (EPSc). The EPSp had a mean MW of 2.0 x 105; about 18% of EPSp had MW over 5 x 104 and 16% below 5 x 103. For heavy metal concentrations ranging 10-100 mg/l, EPS on average removed 99% of Zn2+, 98% of Cu2+, 97% of Cr3+, 85% of Cd2+, 69% of Co2+, 37% of Ni2+, and 26% of CrO4(2-). The relative degrees of metal removals were inconsistent with those reported for the activated sludge process. Each mg of ESP had the capacity to remove up to 1.48 mg of Zn2+, 1.12 mg of Cu2+, 0.83 mg of Cr3+, 0.90 mg of Cd2+, 1.10 mg of Co2+, 0.25 mg each of Ni2+ and CrO4(2-). Results suggest the feasibility of recovering ESP from waste sludge for use as adsorbent. Freundlich isotherm correlated satisfactorily with the adsorption data of Ni2+, Cu2+, Cd2+, and CrO4(2-) (R2 ranging 0.89-0.97), whereas Langmuir isotherm correlated satisfactorily with those of Zn2+, Cr3+ and Ni2+ (R2 ranging 0.93-0.96). Both correlated poorly for those of Co2+.

Adsorption↗

PubMed2001

Inhibition by chromium and cadmium of anaerobic acidogenesis.

The effects of chromium (III) and cadmium on the anaerobic acidogenesis of a simulated dairy waste were examined using serum vials. At Cd dosages less than 20 mg/l, the acidogenesis process was enhanced by the dosage, resulting in a higher degree of acidification, protein conversion, and hydrogen production than the control. At dosages over 20-mg/l, Cd inhibited the acidogenesis. The Cr (III) dosage of 5 mg/l reduced overall volatile fatty acid and alcohol generation, degree of acidification, conversions of lactose, lipid and protein, and total biogas production, with the exception of accumulation of hydrogen and propionate. At dosages exceeding 5 mg/l, Cr (III) had a severe inhibition on the acidogenesis. The Cd concentrations which caused a 50% reduction in total volatile fatty acid and alcohol production, degree of acidification and cumulative gas production were higher than the corresponding values caused by Cr (III), suggesting that Cr (III) was more toxic to acidogenic bacteria than Cd.

Alcohols↗

PubMed2001

[Landfill leachate treatment by anaerobic process and electrochemical oxidation].

This study was conducted to develop a two-stage process of UASB and electrochemical oxidation for the treatment of Hong Kong leachate. The leachate, containing 4750 mg/L of chemical oxygen demand (COD) and 1310 mg/L of ammoniacal nitrogen (NH3-N), was first treated in a UASB (upflow anaerobic sludge blanket) reactor at 37 degrees C. The process removed on average 66% of COD with 6.1 days of hydraulic retention time (HRT), corresponding to an organic loading rate COD of 0.78 g/(L.d). The UASB effluent, which had an average pH of 8.9, COD of 1610 mg/L and NH3-N of 1480 mg/L, was then further treated by electrochemical oxidation in a batch reactor with recirculation. With the addition of 2000 mg/L of chloride (in the form of sodium chloride) and at a current density of 32.3 mA/cm2, 87% of COD and 100% of NH3-N were removed from the UASB effluent in six hours. The energy consumption was < 55 kW.h/kg COD. The final effluent contained no residual NH3-N and only 209 mg/L of COD. In this paper, some basic problems in electrochemical oxidation, such as the effects of the operation parameters, the mechanism of the process, and assessment of the energy requirements were discussed in detail.

Anaerobiosis↗

PubMed2000

Thermophilic acidification of dairy wastewater.

Acidification of simulated dairy wastewater was conducted in an upflow reactor at 55 degrees C. Results showed that the degree of acidification decreased with the increase in chemical oxygen demand (COD) loading rate, from 60.8% at 4 g l(-1) day(-1) to 27.1% at 24 g l(-1) day(-1). Carbohydrate was readily degraded at all loading rates, but degradation of protein and lipid decreased with the increase in loading rate. Most carbohydrate degradation occurred at the reactor bottom, whereas protein was degraded mainly after the carbohydrate became depleted. The predominant acidification products were acetate, propionate, butyrate and ethanol, whereas formate, i-butyrate, valerate, i-valerate, caproate, lactate, methanol, propanol and butanol were present in lesser quantities. The increase in loading rate resulted in the increase of propionate and the decrease of acetate, but had little effect on ethanol and butyrate productions. Only 2.5-8.8% of influent COD was converted to hydrogen and methane. The biomass yield was 0.30-0.43 mg VSS mg(-1) COD.

Alcohols↗

PubMed2000

Quantification of bacterial adhesion forces using atomic force microscopy (AFM).

This study demonstrated that atomic force microscopy (AFM) can be used to obtain high-resolution topographical images of bacteria, and to quantify the tip-cell interaction force and the surface elasticity. Results show that the adhesion force between the Si3N4 tip and the bacteria surface was in the range from -3.9 to -4.3 nN. On the other hand, the adhesion forces at the periphery of the cell-substratum contact surface ranged from -5.1 to -5.9 nN and those at the cell-cell interface ranged from -6.5 to -6.8 nN. The two latter forces were considerably greater than the former one, most likely due to the accumulation of extracellular polymer substance (EPS). Results also show that the elasticity varied on the cell surface.

Aluminum Silicates↗

PubMed2000

[Expression and characterization of HIV-1 Gag p17-p24 protein].

The biological and immunological characteristics of HIV-1 core protein p17-24 expressed by recombinant vaccinia viruses were studied. The results of indirect immunofluorescence assay (I-IFA), Western blot and dot ELISA showed that the two recombinants could express the p24 gag and p17-24 gag fusion proteins in infected cell lines respectively. The electromicroscope observation revealed that the expressed proteins could also assemble into virus-like particles. The recombinant vaccinia viruses can also stimulate mice for the formation of anti HIV-1 Gag p24 antibody. When infected with the recombinant viruses, the chromosome DNA ladder caused by the apoptosis of the BHK cell was observed.

Animals↗

PubMed1996

Two plasma membrane H(+)-ATPase genes expressed in guard cells of Vicia faba are also expressed throughout the plant.

Guard cells modulate stomatal apertures in response to hormones, metabolic demands and environmental stimuli. The guard cell PM H(+)-ATPases play a critical role in this process by generating the electrochemical gradient to drive solute transport and concomitant water flux. The PM H(+)-ATPase activity is specifically regulated by red and blue light, fungal toxins and auxin. To determine if the unique responsiveness of the guard cell PM H(+)-ATPase is due to the expression of a cell-specific isoform, we amplified by PCR, and cloned portions of PM H(+)-ATPase genes VHA1 and VHA2, which are expressed in guard cell protoplasts (GCP). In situ hybridization to leaf tissue sections indicated that VHA1 and VHA2 genes were expressed in guard cells and mesophyll cells but not in epidermal cells or vascular tissues. Furthermore, a gene-specific quantitative reverse transcription (RT)-PCR detected VHA1 and VHA2 mRNAs in both GCP and mesophyll cell protoplast mRNA as well as in mRNA isolated from roots, leaves, stems and flowers. Thus, two PM H(+)-ATPase genes expressed in guard cells are also expressed in many other tissues and cell types. This suggests that the unique responsiveness of the guard cell PM H(+)-ATPases to environmental stimuli results from cell-specific signal transduction pathways rather than the expression of a cell-specific PM H(+)-ATPase.

Cell Membrane↗

PubMed1991

Inward-rectifying K+ channels in guard cells provide a mechanism for low-affinity K+ uptake.

The molecular mechanisms by which higher plant cells take up K+ across the plasma membrane (plasmalemma) remain unknown. Physiological transport studies in a large number of higher plant cell types, including guard cells, have suggested that at least two distinct types of K(+)-uptake mechanisms exist, permitting low-affinity and high-affinity K+ accumulation, respectively. Recent patch clamp studies have revealed the presence of inward-conducting (inward-rectifying) K+ channels in the plasma membrane of higher plant cells. Research on guard cells has suggested that these K+ channels provide a major pathway for proton pump-driven K+ uptake during stomatal opening. In the present study the contribution of inward-rectifying K+ channels to higher plant cell K+ uptake was investigated by examining kinetic properties of guard cell K+ channels in Vicia faba in response to changes in the extracellular K+ concentration. Increasing the extracellular K+ concentration in the range from 0.3 mM to 11.25 mM led to enhancement of inward K+ currents and changes in current-voltage characteristics of K+ channels. The increase in K+ conductance as a function of the extracellular K+ concentration revealed a K(+)-equilibrium dissociation constant (Km) of approximately 3.5 mM, which suggests that inward-rectifying K+ channels can function as a molecular mechanism for low-affinity K+ uptake. Lowering the extracellular K+ concentration in the range from 11 mM to 1 mM induced negative shifts in the activation potential of K+ channels, such that these channels function as a K+ sensor, permitting only K+ uptake. At low extracellular K+ concentrations of 0.3 mM K+, inward-rectifying K+ channels induce hyperpolarization. Results from the present study suggest that inward-rectifying K+ channels constitute an essential molecular mechanism for plant nutrition and growth control by providing a K(+)-sensing and voltage-dependent pathway for low-affinity K+ uptake into higher plant cells and additionally by contributing to plasma membrane potential regulation.

Cell Membrane↗

PubMed1991

Treatment of wastewater from a whey processing plant using activated sludge and anaerobic processes.

Wastewater from a whey processing plant was treated in two on-site pilot plants, a three-stage activated sludge plant and an anaerobic reactor, each of which had the capacity of treating 230 L/h of wastewater. The activated sludge treatment was very effective. It reduced 99% of 5-d biochemical oxygen demand of the plant wastewater (from an average of 1062 to 9 mg/L) and 91% of total Kjeldahl nitrogen (from 109 to 10 mg/L) after a total retention time of 19.8 h. The intermediate 5-d biochemical oxygen demand reductions were 86% after 3.8 h in the first stage and 97% after another 8 h in the second stage. The completely mixed anaerobic reactor reduced only 87% of 5-d biochemical oxygen demand after 2 d of retention. However, with an additional 8 h of activated sludge treatment the total 5-d biochemical oxygen demand was reduced by 99%. Both pilot plants were operated smoothly in spite of the considerable fluctuations in pollutant levels of the plant wastewater.

Anaerobiosis↗

PubMed1991

Duration of immunity following immunization with live measles vaccine: 15 years of observation in Zhejiang Province, China.

The duration of immunity following measles vaccination of 2882 immunized children has been investigated in a closed region of China for 15 years. A total of 1002 of the children were treated as primary immunization subjects, and 1547 as reimmunization subjects. These two cohorts were not in contact with known wild measles virus over the whole observation period, and the results obtained probably reflected the antibody responses to measles vaccine alone. The remaining 333 vaccinees came into contact with wild measles virus, and this permitted evaluation of the protective effect of the measles vaccines tested: 4 children experienced very mild clinical measles, and 329 experienced subclinical infection, including 12 who had had undetectable haemagglutination-inhibition antibodies for 9-10 years. These results indicate that the immunity induced by successful primary immunization may persist for at least 15 years. Within this period, a second dose of vaccine only induces low antibody responses which decrease rapidly to their original levels. This provides strong evidence that the immunity produced by primary immunization is long-lasting. However, there were some indications that reimmunization might produce better effects if live attenuated measles virus were used with a longer interval between doses.

Adolescent↗