J. P. Barford

Selenium in sediments, pore waters and benthic infauna of Lake Macquarie, New South Wales, Australia

Measurements of selenium in sediments and benthic infauna of Lake Macquarie, an estuary on the east coast of Australia, indicate that sediments are a significant source of selenium in the lakes food web. Analysis of surficial sediment samples indicated higher selenium concentrations near what are believed to be the main industrial sources of selenium to the lake: a smelter and a power station. Sediment cores taken from sediments in Mannering Bay, near a power station at Vales Point, contained an average of 12 times more selenium in surficial sections than sediment cores from Nords Wharf, a part of the lake remote from direct inputs of selenium. The highest selenium concentration found in Mannering Bay sediments (17.2 μg/g) was 69 times the apparent background concentration at Nords Wharf (0.25 μg/g). Pore water concentrations in Mannering Bay were also high, up to 5 μg/l compared to those at Nords Wharf which were below detection limits (0.2 μg/l). Selenium concentrations in muscle tissues of three benthic-feeding fish species (Mugil cephalus, Platycephalus fuscus, Acanthopagrus australis) were significantly correlated (p<0.05) with surficial sediment selenium concentration. Selenium concentrations in polychaetes and molluscs of Mannering Bay were up to 58 times higher than those from Nords Wharf. Two benthic organisms, the eunicid polychaete Marphysa sanguinea and the bivalve mollusc Spisula trigonella, were maintained at different densities in selenium-spiked sediments. Both animals accumulated selenium from the spiked sediment, confirming that bioaccumulation from contaminated sediments occurs. Collectively, these data suggest that benthic food webs are important sources of selenium to the fish of Lake Macquarie.

An Unstructured Kinetic Model of Macromolecular Metabolism in Batch and Fed-batch Cultures of Hybridoma Cells Producing Monoclonal Antibody

Abstract Growth profiles of the batch and fed-batch culture of hybridoma cells producing monoclonal antibody were simulated using an unstructured model. The model describes the production of cellular macromolecules and monoclonal antibody, the metabolism of glucose and glutamine with the production of lactate and ammonia, and the profiles of cell growth in batch and fed-batch culture. Equations describing the cells arrested in G1 phase [T.I. Linardos, N. Kalogerakis, L.A. Behie, Biotechnol. Bioeng. 40 (1992) 359–368; E. Suzuki, D.F. Ollis, Biotechnol. Bioeng. 34 (1989) 1398–1402] were included in this model to describe the increase of the specific antibody productivity in the near-zero specific growth rate, which was observed in the recent experiments in fed-batch cultures of this study and the semi-continuous culture of hybridoma cells [S. Reuveny, D. Velez, L. Miller, J.D. Macmillan, J. Immnol. Methods 86 (1986) 61–69]. This model predicted the increase of specific antibody production rate and the decline of the specific production rate of cellular macromolecules such as DNA, RNA, protein, and polysaccharide in the late exponential and decline phase of batch culture and at lower specific growth rates in the fed-batch culture.

Biosensor for rapid phosphate monitoring in a sequencing batch reactor (SBR) system

A thick-film phosphate biosensor based on hydrogel immobilized pyruvate oxidase (POD) has been developed for rapid phosphate process control monitoring in an experimental sequencing batch reactor (SBR) system. We have employed a phosphate biosensor in an off-line monitoring of phosphate concentrations in a bench scale SBR. Measurements with biosensor show a good correlation (r2=0.98) with those of commercial colorimetric phosphate testing kits. The signal response time was 1 min with a detection limit of 5 microM. The biosensor method showed a good operational stability, needed less experimental procedures and a small sample size (approximately 20 microl). This allows its practical application for rapid phosphate measurements to obtain real time process data in a SBR system.

Continuous tower fermentation for power ethanol production

SummaryThe capability of the continuous tower fermenter to accumulate and retain high cell densities (70–90 g dry wt/1) when using naturally flocculant yeasts is demonstrated with semi-defined glucose feed at concentrations of 120–200 g/1 and high hydraulic loadings. Conversion and ethanol productivity data are given as a function of throughput and feed glucose concentration.

A study of hybridoma cell growth and antibody production kinetics in continuous culture

A detailed study of cell growth and antibody production kinetics in continuous culture found that the specific rate of antibody production reached a maximum saturated profile at a specific growth rate less than the maximum. This observation is novel and of importance in the understanding of the mechanism of antibody production and/or antibody transport.

Induced flocculation of yeasts for use in the tower fermenter

SummaryIt has been demonstrated that it is possible to induce flocculation in a yeast normally classified as non-flocculent. Further, it has been possible to accumulate and retain a very high cell density of this yeast in an upflow floc (tower) fermenter and to rapidly and efficiently convert glucose to ethanol. The method outlined for inducing flocculation appears to greatly broaden the range of organisms that might be considered for use in the tower fermenter, thus greatly enhancing this simple mode of continuous operation.

THE DEVELOPMENT OF GRANULATION IN AN UPFLOW FLOC DIGESTER AND AN UPFLOW ANAEROBIC SLUDGE BLANKET DIGESTER TREATING CANE JUICE STILLAGE

SummaryThe use of synthetic polyelectrolytes in the Upflow Floc digester during the treatment of high strength cane juice stillage, resulted in a more rapid accumulation of biomass and promoted granule formation at an earlier stage compared to a control upflow anaerobic sludge blanket digester (UASB). In the Upflow Floc reactor the granules were composed of rod shaped organisms, whereas in the UASB the granules were primarily filamentous. Both types of granules had good settling properties and high activities.

Mesophilic semi-continuous anaerobic digestion of palm oil mill effluent

Abstract A semi-continuous digester was used to degrade palm oil mill effluent (POME) under mesophilic conditions. A space loading of 12·6 kg COD/m 3 day (hydraulic residence time of 5·6 days) was maintained for a month, with soluble COD removals being greater than 97%. This rate is significantly faster than the rates achieved in previously reported mesophilic studies.

Anaerobic digestion of wool scouring wastewater in a digester operated semi-continuously for biomass retention

An anaerobic digester, operated semi-continuously in order to retain high concentrations of biomass in the digester, was used to treat wool scouring wastewater. At a space load of 9·9 kg COD m−3 day −1 (hydraulic retention time, 2·8 days) >56% of the COD and >47% of the grease were removed. At these efficiencies, this rate was estimated to be at least 2·5·3· times greater than that which would be achieved in a continuously stirred digester. Preliminary studies of enzymatic pretreatment of the scouring effluent showed that significantly improved treatment rates and/or efficiencies could be achieved—i.e. >70% removal of both the COD and grease at a space load of 12 kg COD m−3 day−1. It is unlikely that any substancial levels of flocculation would develop in this system and it is expected that the moderate use of polyelectrolytes would be required to help maintain the VSS concentration in the reactor.

Batch growth and transport kinetics of utilization of mixtures of sucrose and maltose by Saccharomyces cerevisiae

Abstract Sucrose and maltose are commonly used sugars in brewing, baking and/or ethanol production industries. Since both sugars have been shown to be transported directly into the yeast cells of Saccharomyces cerevisiae (for maltose, it is the only mode of utilization), the way the two transport systems interact when the two disaccharides are present in mixture was investigated using both fermentation and radiometric studies. Two strains of S. cerevisiae were used in this study: 248 UNSW 703100 (laboratory strain) and A11 (industrial strain). The yeast cells were adapted on the disaccharides for up to 14 d before fermentation or radiometric studies were carried out. In batch culture studies, the adapted cells on either maltose for 2 d or sucrose for 14 d were grown on mixtures of sucrose and maltose containing different proportions of the two disaccharides. In both strains, the growth on the mixture was diauxic with sucrose and its hydrolysis products being utilized first. In radiometric studies, the affinity constant for maltose in maltose-adapted cells of strain 248 UNSW 703100 increased from 4.3 mM when the cells were incubated with [U-14C] maltose to 19.3 mM when incubated with equimolar mixture of [U-14C] maltose and unlabelled sucrose. The apparent affinity constant for sucrose transport in sucrose-adapted cells increased from 6.4 mM when the cells were incubated with [U-14C] sucrose to 18.9 mM when incubated with equimolar mixture of [U-14C] sucrose and unlabelled maltose.