Production of bacteriocins by Streptococcus bovis strains from Australian ruminants.

AIMS: To examine the prevalence of bacteriocin production in Streptococcus bovis isolates from Australian ruminants and the feasibility of industrial production of bacteriocin. METHODS AND RESULTS: Streptococcus bovis strains were tested for production of bacteriocin-like inhibitory substances (BLIS) by antagonism assay against Lactococcus lactis. BLIS production was associated with source animal location (i.e. proximity of other bacteriocin-positive source animals) rather than ruminant species/breed or diet. One bacteriocin showing strong inhibitory activity (Sb15) was isolated and examined. Protein sequence, stability and activity spectrum of this bovicin were very similar to bovicin HC5. Production could be increased through serial culturing, and increased productivity could be partially maintained during cold storage of cultures. CONCLUSIONS: BLIS production is geographically widely distributed in Eastern Australia, and it appears that the bacteriocin(+) trait is maintained in animals at the same location. The HC5-like bacteriocin, originally identified in North America, is also found in Australia. Production of bacteriocin can be increased through serial culturing. SIGNIFICANCE AND IMPACT OF THE STUDY: The HC5-like bacteriocins appear to have a broad global distribution. Serial culturing may provide a route towards commercial manufacturing for use in industrial applications, and purified bacteriocin from S. bovis Sb15 could potentially be used to prevent food spoilage or as a feed additive to promote growth in ruminant species.

Bacteriological examination of ballast water in Singapore Harbour by flow cytometry with FISH.

In this study the concentrations of total bacteria, enterobacteria, Vibrio spp., and E. coli have been compared for ballast water samples taken from ships in Singapore Harbour. The cell concentrations were enumerated using FISH and flow cytometry. The data were highly variable, reflecting the many influences upon ballast water as it is utilized in the shipping industry. The concentration of bacterial species was determined as a proportion of the total concentration of cells for the ballast water sampled. For the ballast water sampled these concentrations were 0.67-39.55% for eubacteria, 0-2.46% for enterobacteria, 0.18-35.82% for Vibrio spp., and 0-2.46% for E. coli. Using FISH and flow cytometry, an informative determination of the bacterial hazards of ship ballast water can be made.

Characterization of a high-productivity recombinant strain of Zymomonas mobilis for ethanol production from glucose/xylose mixtures.

The fermentation characteristics of a recombinant strain of Zymomonas mobilis ZM4(pZB5) capable of converting both glucose and xylose to ethanol have been further investigated. Previous studies have shown that the strain ZM4(pZB5) was capable of converting a mixture of 65 g/L of glucose and 65 g/L of xylose to 62 g/L of ethanol in 48 h with an overall yield of 0.46 g/g. Higher sugar concentrations (e.g., 75/75 g/L) resulted in incomplete xylose utilization (80 h). In the present study, further kinetic evaluations at high sugar levels are reported. Acetate inhibition studies and evaluation of temperature and pH effects indicated increased maximum specific uptake rates of glucose and xylose under stressed conditions with increased metabolic uncoupling. A high-productivity system was developed that involved a membrane bioreactor with cell recycling. At sugar concentrations of approx 50/50 g/L of glucose/xylose, an ethanol concentration of 50 g/L, an ethanol productivity of approx 5 g/(L.h), and a yield (YP/S) of 0.50 g/g were achieved. Decreases in cell viability were found in this system after attainment of an initial steady state (40-60 h); a slow bleed of concentrated cells may be required to overcome this problem.