Biomedical subjects

F W Bai

Publications and source records attributed to F W Bai.

7 recordsLinked to original sources

PubMed2006

Intrinsic kinetics of continuous growth and ethanol production of a flocculating fusant yeast strain SPSC01.

The intrinsic kinetics of continuous yeast cell growth and ethanol production for a self-flocculating fusant yeast strain SPSC01 was investigated by means of mechanically dispersing the flocs and correspondingly established floc size distribution on-line monitoring technique using the focused beam reflectance measurement system, through which the floc intra-particle mass transfer limitation was effectively eliminated, but its ethanol formation metabolism was not affected. Modified kinetic models were developed, which can be used to predict the continuous kinetic behaviors of SPSC01, especially when low dilution rates are applied and limiting substrate concentrations are undetectable and almost all kinetic models developed previously are failed in predicting corresponding kinetic behaviors. Both substrate and product inhibitions reported for freely suspended yeast cell ethanol production were also observed for SPSC01 when high gravity media were fed and relatively high levels of residual sugar and ethanol presented. Model parameters were evaluated through numerical calculation method and validated by experimental data mu = 0.584C(s)/0.155 + C(s) + C(2)(s)/160.7(1 -P/125)(3.68) + 0.004 for growth, nu = 1.998C(s)/0.427 + C(s) + C(2)(s)/366.7(1- P/125)(1.72) + 0.060 for ethanol production These intrinsic kinetic models can be further used to develop the observed kinetic models that quantitatively correlate the impact of the self-flocculating yeast cell size distributions on their apparent rates for yeast cell growth, substrate uptake and ethanol production and optimize the ethanol production process.

Algorithms↗

PubMed2005

Online monitoring and characterization of flocculating yeast cell flocs during continuous ethanol fermentation.

Both intrinsic and observed kinetic investigations for those ethanol fermentations using self-flocculated yeast strains have been hindered by the lack of real online monitoring techniques and proper characterization methods for the flocs. An optical detecting technique, the focused beam reflectance measurement probe developed by Lasentec (Redmond, WA) was inserted into a fermentor to monitor the floc chord length distributions. Using a simulating system composed of the floc-buffer suspensions, the total floc chord length counts per second were directly correlated with the floc biomass concentrations so that the floc biomass concentrations can be in situ detected. Furthermore, a characterization method of the flocs was established by properly weighted treatments of the detected floc chord length distributions. When a real yeast floc ethanol fermentation system was detected during its intrinsic kinetic investigations in which the floc size needed to be controlled at a level of micrometer scale to eliminate inner mass transfer limitations, it was found and validated that CO(2) produced during fermentation exerted significant disturbances. By applying 1/length-weighted treatment, these disturbances were effectively overcome.

Bioreactors↗

PubMed2004

Parameter oscillations in a very high gravity medium continuous ethanol fermentation and their attenuation on a multistage packed column bioreactor system.

The quasi-steady-states, marked by small fluctuations of residual glucose, ethanol, and biomass concentrations, and sustainable oscillations marked by big fluctuations of these monitored fermentation parameters were observed during the continuous ethanol fermentation of Saccharomyces cerevisiae when very high gravity media were fed and correspondingly high ethanol concentrations reached. A high ethanol concentration was shown to be one of the main factors that incited these oscillations, although the residual glucose level affected the patterns of these oscillations to some extent. The lag response of S. cerevisiae to high ethanol stress that causes the shifts of morphology, viability loss, and death of yeast cells is assumed to be one of the probable mechanisms behind these oscillations. It was predicted that the longer the delay of this response was, the longer the oscillation periods would be, which was validated by the experimental data and the comparison with the oscillatory behaviors reported for the ethanologen bacterium, Zymomonas mobilis. Furthermore, three tubular bioreactors in series were arranged to follow a stirred tank bioreactor to attenuate these oscillations. However, exaggerated oscillations were observed for the residual glucose, ethanol, and biomass concentrations measured in the broth from these tubular bioreactors. After the tubular reactors were packed with Intalox ceramic saddle packing, these oscillations were effectively attenuated and quasi-steady-states were observed during which there were very small fluctuations of residual glucose, ethanol, and biomass within the entire experimental run.

Apoptosis↗

PubMed2004

Continuous ethanol production and evaluation of yeast cell lysis and viability loss under very high gravity medium conditions.

A combined bioreactor system, composed of a stirred tank and a three-stage tubular bioreactor in series and with a total working volume of 3260 ml, was established. Continuous ethanol production was carried out using Saccharomyces cerevisiae and a very high gravity (VHG) medium containing 280 g l(-1) glucose. An average ethanol concentration of 124.6 g l(-1) or 15.8% (v) was produced when the bioreactor system was operated at a dilution rate of 0.012 h(-1). The yield of ethanol to glucose consumed was calculated to be 0.484 or 94.7% of its theoretical value of 0.511 when ethanol entrapped in the exhaust gas was incorporated. Meanwhile, quasi-steady states and non-steady oscillations were observed for residual glucose, ethanol and biomass concentrations for all of these bioreactors during their operations. Models that can be used to predict yeast cell lysis and viability loss were developed.

Biomass↗

PubMed2002

Selection and expression of peptides which can change the conformation of p20 protein of rice stripe virus.

Phages with high affinity to the P20 protein of rice stripe virus (RSV) were enriched from phage-displayed random 12-mer peptide library after three rounds of phage display screening. Nine different peptides from the enriched library were selected by enzyme-linked immunosorbent assay (ELISA). The P20 protein from raw extracts of rice leaves infected with RSV could be detected by those 9 peptides displayed on the phage, which suggested that a peptide could be an effective tool for diagnosis of RSV in rice and planthopper. Circular dichroism (CD) spectra of P20 fusion proteins with the binding phages and non-binding phages showed that the conformation of P20 protein was changed after binding to each of the 9 selected 12-mer peptides, which suggested that these peptides might disrupt the function of the P20 protein. Thereafter, those peptides might be used to develop plant resistance and disrupt virus transmission. Three of the 12-mer peptide genes were fused with the glutathione-S-transferase (GST) gene in the vector pGEX 3X. The fusion proteins were obtained from an Escherichia coli expression system and purified. The fusion proteins might have a potential to develop a plant peptide-based resistance to its pathogens and virus diagnosis. It also provided a tool (i) to confirm the inhibition of the function of P20 protein by the fusion peptides in vivo, and (ii) to detect the function of P20 protein and the interaction between the virus and its vector.

Electrophoresis, Polyacrylamide Gel↗

PubMed2002

Selection of phage-display peptides that bind specifically to the outer coat protein of Rice black streaked dwarf virus.

Several peptides that could bind specifically to the outer coat protein encoded by the S10 gene of Rice black streaked virus (RBSDV) were isolated from a phage-display random 12-mer peptide library. The sequence analysis showed that the amino acid motif (K)K**(*)P, the asterisk denoting any amino acid, might be the core sequence by which the peptides bind to the target protein. The peptide 1 that had a high affinity to RBSDV outer coat protein was synthesized by a chemical method and its fusion protein with glutathione-S-transferase (GST) was produced in an Escherichia coli expression system. The dot and Western blot analyses indicated that RBSDV could be detected with a high sensitivity in crude extracts of diseased plant leaves using a purified GST fusion protein. The circular dichroism (CD) spectroscopy revealed that the synthesized binding peptide but not a nonbinding peptide could bring about a marked change in the conformation of outer coat RBSDV protein. Since the protein functions only when it has correct conformation, the peptides binding specifically to it could possibly disturb the function of the virus outer coat protein and might be used to block the transmission pathway of the virus. Summing up, as these peptides showed a high specificity and sensitivity and diagnostic potential for RBSDV, they may represent the basis of a novel strategy for development of resistance to RBSDV.

Artificial Gene Fusion↗

PubMed2001

Identification of rice black streaked dwarf virus in different cereal crops with dwarfing symptoms in China.

This report describes isolation of virus particles from plants of rice, maize, wheat and sorghum with symptoms of dwarfing collected from two provinces of China, purification of double-stranded RNA (dsRNA) from the virus particles, and synthesis of full-length cDNAs of genome segments 9 (S9) and 10 (S10) by reverse transcription-polymerase chain reaction (RT-PCR). Sequence analysis showed that the S9 sequences of the Chinese isolates and a Japanese rice black-streaked disease virus (RBSDV) isolate were very similar (89.1-89.6% homology at nucleotide level and 92.3-92.9% and 95.8-98.6% homology at amino acid level for ORF1 and ORF2, respectively). Analogical similarity was found also for the S10 sequences of the isolates under comparison: 93.0-95.4% homology at nucleotide level and 96.2-97.0% homology at amino acid level. However, there was a relatively lower similarity for S9 and S10 segments ofthe Chinese isolates and an Italian maize rough dwarf virus (MRDV) isolate. The phylogenetic analysis indicated that the Chinese isolates that infect rice, maize, wheat and sorghum and cause similar symptoms could represent the same virus species, RBSDV.

Amino Acid Sequence↗