Broderick E. Eribo

Isolation and Characterization of Vibrio tubiashii Outer Membrane Proteins and Determination of a toxR Homolog

ABSTRACT Outer membrane proteins (OMPs) expressed by Vibrio tubiashii under different environmental growth conditions were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, N-terminal amino acid sequencing, and PCR analyses. Results showed the presence of a 38- to 40-kDa OmpU-like protein and ompU gene, a maltoporin-like protein, several novel OMPs, and a regulatory toxR homolog.

Production of poly-(β-hydroxybutyrate) from saponified Vernonia galamensis oil by Alcaligenes eutrophus

Saponified vernonia oil was converted exclusively to poly(β-hydroxybutyrate) (PHB) by Alcaligenes eutrophus in a single-stage batch culture. After harvesting, centrifugation followed by lyophilization, the resulting dried cells contained up to 42.8 wt% PHB having a peak molecular mass of 381 863 Da, weight-average molecular mass of 308 390 Da, and a polydispersity of 1.1. The PHB had a melting point (Tm) range of 163–174°C with a maximum at 172°C (lit. Tm, 175°C), and heat of fusion of 18.43 cal g−1. Fermentation performed under varying conditions of nitrogen limitation indicated that there was no significant effect of nitrogen concentration on the molecular mass of PHB produced from vernonia oil by A. eutrophus.

Non-Edible Vernonia galamensis Oil and Mixed Bacterial Cultures for the Production of Polyhydroxyalkanoates

Since the oil crisis of the 1970s much attempt has been made, albeit with varying degrees of success, to source the ideal substrate and bacteria for the production of PHA. The non-edible, naturally epoxidized seed oil from Vernonia galamensis and mixed cultures consisting of Alcaligenes latus (ATCC 29712), Cupriavidus necator (ATCC 17699), Escherichia coli (DH5α) and Pseudomonas oleovorans (ATCC 29347), were evaluated for PHA production under batch and fed-batch fermentations. PHA production, optimized by the mixed culture of E. coli and C. necator, was 0.4-19% (%wt/wt, cdw) for batch and fed-batch fermentations. Analyses of PHA by Matrix Assisted Laser Desorption Ionization- Time of Flight Mass Spectrometry (MALDI-TOF MS) and Gas Chromatography Mass Spectrometry (GC/MS) identified the 3-hydroxybutyrate (3HB) monomeric unit. The PHA ester bond stretching vibration (C=O), was confirmed at absorption 1740.66 cm-1, using Fourier Transform Infrared Spectroscopy (FTIR). Gel Permeation Chromatography (GPC) indicated peak molecular weights between 3.8×103-1.12×106 Da with melting points (Tm), 60-90°C. The data further illustrates that inedible oils could be the ideal carbon source for the production of PHA.

Characterization of partially transesterified poly(β‐hydroxyalkanoate)s using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used for the characterization of a partially transesterified poly(beta-hydroxyalkanoate), PHA, polymer produced by the bacterial strain Alcaligenes eutrophus using saponified vegetable oils as the sole carbon sources. The transesterification was carried out separately under acidic and basic conditions to obtain PHA oligomers weighing less than 10 kDa. The intact oligomers were detected in their cationized [M + Na](+) and [M + K](+) forms by MALDI-TOFMS. A composition analysis, using the MALDI-TOF spectra, indicate that the oligomers obtained via acid catalysis were terminated with a methyl 3-hydroxybutyrate end group, and those obtained by base catalysis had a methyl crotonate (olefinic) termination. In addition to HB (hydroxy butyrate), the oligomers were found to contain a small percentage of HV (hydroxy valerate). This was independently confirmed using gas chromatography/mass spectrometry (GC/MS). In comparison, the analysis of a commercial PHA polymer, transesterified under identical conditions, only showed the presence of HB, i.e. a pure PHB homopolymer. Copyright 1999 John Wiley & Sons, Ltd.

Leptospire Genomic Diversity Revealed by Microarray-Based Comparative Genomic Hybridization

ABSTRACT Comparative genomic hybridization was used to compare genetic diversity of five strains of Leptospira (Leptospira interrogans serovars Bratislava, Canicola, and Hebdomadis and Leptospira kirschneri serovars Cynopteri and Grippotyphosa). The array was designed based on two available sequenced Leptospira reference genomes, those of L. interrogans serovar Copenhageni and L. interrogans serovar Lai. A comparison of genetic contents showed that L. interrogans serovar Bratislava was closest to the reference genomes while L. kirschneri serovar Grippotyphosa had the least similarity to the reference genomes. Cluster analysis indicated that L. interrogans serovars Bratislava and Hebdomadis clustered together first, followed by L. interrogans serovar Canicola, before the two L. kirschneri strains. Confirmed/potential virulence factors identified in previous research were also detected in the tested strains.