Biomedical subjects

Han-Qing Yu

Publications and source records attributed to Han-Qing Yu.

44 records · Page 3Linked to original sources

PubMed2004

Thermodynamic analysis of product formation in mesophilic acidogenesis of lactose.

Thermodynamic analysis on the acidogenesis of lactose was performed to evaluate the different acidogenic patterns and mechanisms by using Gibbs free energy calculation. Batch acidogenesis of lactose was investigated by using an enriched culture at 37 degrees C, pH 5.5 and varied substrate levels. In addition to usual acidogenic products, i-butyrate, valerate, i-valerate, caproate, and propanol were also produced at a significant level. Thermodynamic analysis shows that valerate might be formed through the reaction requiring hydrogen as electron donor and consuming of propionate and carbon dioxide. Caproate was most likely produced directly from butyrate, hydrogen, and carbon dioxide. The minimum amount of Gibbs free energies needed to sustain isomerization of butyrate and valerate were approximately 5.7-5.8 and 4.5-4.6 kJ/mol, respectively. Propanol was produced from acetate, hydrogen, and carbon dioxide with a minimum amount of Gibbs free energy of 41.8-42.0 kJ/mol. Formation of butanol was controlled more by substrate level or population dynamics than by thermodynamics.

Alcohols↗

PubMed2004

Extraction of extracellular polymeric substances from the photosynthetic bacterium Rhodopseudomonas acidophila.

Among the four methods for extracting extracellular polymeric substances (EPS) from Rhodopseudomonas acidophila (EDTA, NaOH, H(2)SO(4), heating/centrifugation), EDTA extraction was found to be the most effective. The contents of the major components of EPS from R. acidophila, i.e., carbohydrate, protein and nucleic acid, were 6.5, 58.4 and 5.4 mg g(-1) dry cells, respectively. The optimum extraction time was 1-3 h and the EDTA dosage was approximately 2.8 g g(-1) dry cells. Under these conditions, no cell lysis was observed. The EPS content and the percentage of the three main components were greatly dependent on the extraction method. The intensity of absorption peaks for photosynthetic pigments in the UV-visible spectrum of bacteria remained unchanged prior to and after EDTA extraction; and no pigment peaks appeared in the EPS spectrum. This suggests that few cells were destroyed and lysis did not occur. UV-visible spectrum analysis, an easy and rapid technique, could be used to monitor cell lysis during EPS extraction from R. acidophila.

Bacterial Proteins↗

PubMed2004

Reductive degradation of nitrobenzene in aqueous solution by zero-valent iron.

The reductive degradation of nitrobenzene (NB) by zero-valent iron was investigated. Experimental results showed that the degradation of NB was influenced by pH and NB concentration. The optimum pH value was found to be 3.0 for the reductive degradation of NB in the tested pH ranges of 3.0-12.0. The formation rate of aniline, a major reductive product of NB, followed zero-order kinetics at various pH levels. Furthermore, GC/MS analysis showed that aniline, azobenzene and azoxybenzene were the reductive products of NB by zero-valent iron. With the analysis of the products with GC/MS and FTIR, possible reductive pathways of NB by zero-valent iron were suggested.

Aniline Compounds↗

PubMed2004

Degradation of calcium lignosulfonate using gamma-ray irradiation.

Gamma-ray irradiation was proven to be a promising means for the removal of calcium lignosulfonate (CaLS). At a dose rate of 55Gy min(-1), over 90% of CaLS was mineralized to CO(2), H(2)O and sulfates within 3-d irradiation. The degradation of CaLS with the initial CaLS concentrations ranging from 40 to 200mg l(-1) followed zero-order kinetics at the dose rates of 16-150Gy min(-1). The zero-order degradation rate constant was functionally related with irradiation dose rate. Experiments performed with or without addition of radical scavengers demonstrated that the role of *OH was predominant in CaLS degradation and the reductive species made minor contributions to CaLS degradation. Addition of appropriate amounts of H(2)O(2) significantly enhanced the mineralization of CaLS, e.g., addition of 10mM H(2)O(2) at a dose rate of 55Gy min(-1) elevated the mineralization rate constant by five times. The addition of Fenton's reagent to irradiated CaLS solutions facilitated the degradation of CaLS, but no obviously synergistic effect was observed.

Gamma Rays↗

PubMed2004

Radiation-induced degradation of polyvinyl alcohol in aqueous solutions.

The degradation of polyvinyl alcohol (PVA) by gamma-ray irradiation was investigated. Degradation efficiency of PVA was influenced by several factors, such as initial PVA concentration, dose rate, pH, and the addition of H2O2. The degradation kinetics depended on initial PVA concentration and dose rate. At a relatively lower PVA concentration, e.g., 180 mg/L, and a higher dose rate, e.g., 55.7 Gy/min, the degradation followed pseudo-first-order kinetics. On the contrary, at a higher PVA concentration, e.g., 500 mg/L, but a lower dose rate, e.g., 12.1 Gy/min, a pseudo-zero-order reaction occurred. The removal of PVA was more effective under acidic or alkaline conditions than that under neutral conditions. At a certain dose rate there was an optimal dosage of H2O2 to facilitate the degradation of PVA. For instance, at a dose rate of 17.2 Gy/min, the optimal H2O2 dosage was found to be about 2.5 mmol/L. Radical scavenging experiments, total organic carbon determination, and FTIR analysis on the degradation products demonstrated that PVA radiolysis was initiated by *OH and H*, leading to chain scission and formation of ketones/enols. Ultimately, complete mineralization of PVA was achieved.

Gamma Rays↗

PubMed2004

Biological hydrogen production by enriched anaerobic cultures in the presence of copper and zinc.

Batch experiments were carried out to examine the productions of hydrogen and volatile fatty acids from glucose by enriched anaerobic culture in the presence of Cu and Zn. Results showed the specific hydrogen production rate was enhanced by the dosage of Cu at 50-100 mg/dm3 or the dosage of Zn at 10-250 mg/dm3, but was inhibited by Cu over 200 mg/dm3 or Zn at 500 mg/dm3. The hydrogen production yield was enhanced by Cu of 5-400 mg/dm3 or Zn of 5-500 mg/dm3. Productions of acetate and propionate were inhibited by Cu of 5-400 mg/dm3 or Zn of 5-500 mg/dm3. On the other hand, production of butyrate was stimulated, whereas production of ethanol was not affected. In terms of the CI,50 values. Cu was more toxic than Zn. The modified Gompertz equation was able to properly describe the cumulative hydrogen production in the presence of Cu or Zn.

Bacteria, Anaerobic↗

PubMed2004

Roles of pH in biologic production of hydrogen and volatile fatty acids from glucose by enriched anaerobic cultures.

Batch experiments were carried out to study the roles of pH in the biologic production of hydrogen and volatile fatty acids from glucose by enriched anaerobic cultures. The results showed that 95-99% of glucose in wastewater was acidified at 30 degrees C and pH 4.0-8.5. Hydrogen yield fluctuated between 1.30 and 1.57 mol of H2/mol of glucose when the reactor was operated at pH 4.0-5.0. However, a further increase in pH led to a considerable decrease in hydrogen yield, especially for the cases at pH 7.5 and 8.0. Acetate, propionate, butyrate, and ethanol were the key products of acidogenesis. Production of butyrate was favored at pH 4.0-5.0, whereas production of acetate was favored at pH 6.0-8.0. A modified Gompertz equation is able to properly describe the batch production of hydrogen from glucose. The optimum pH for the specific hydrogen production was found to be 5.5, close to 5.7, the optimum pH calculated using a semiempirical model.

Bacteria, Anaerobic↗

PubMed2004

Hydrogen production from propionate by Rhodopseudomonas capsulata.

Hydrogen production from propionate at various concentrations by Rhodopseudomonas capsulata, a purple nonsulfur bacterium, was studied at a temperature of 31 degrees C, a pH of 7.0, and an illumination intensity of 3000 Lux. Among the six levels of propionate, 3.84 g/L was found to be the optimum propionate concentration for H2 production in terms of substrate utilization efficiency, H2 percentage, cumulative H2 production, and H2 yield. A modified Gompertz equation was able to describe properly the production of H2 from propionate. A comparative study of H2 production with acetate, propionate, and butyrate at 40 mM showed that, as a substrate for H2 production by R. capsulata, propionate was better than butyrate, but less favorable than acetate.

Acetic Acid↗