John R. Duncan

Effect of α-Tocopherol Succinate on Free Radical and Lipid Peroxidation Levels in BL6 Melanoma Cells

Numerous studies have proposed a radical or oxidant involvement in a number of degenerative diseases such as cancer. This has led to suggestions that the supplementation of antioxidants such as alpha-tocopherol (vitamin E) may function to reduce the growth of cancer. In this study, a nonmalignant Monkey kidney (LLCMK) and a malignant Murine melanoma (BL6-F10) cell line were supplemented with varying levels of alpha-Tocopherol acid succinate (vitamin E succinate) ranging from 1 to 10 microg/ml. BL6-F10 cells supplemented with 5, 7, and 10 microg/ml vitamin E succinate, showed significant decreases in cell proliferation, and this decrease was accompanied by a concomitant increase rather than a decrease in the levels of free radicals and lipid peroxidation. LLCMK cells supplemented with 1-10 microg/ml vitamin E succinate showed no significant increase or decrease in growth, while the levels of lipid peroxidation were shown to be insignificantly elevated at 5, 7, and 10 microg/ml vitamin E succinate. Free radical levels in LLCMK cells were significantly decreased at 1 microg/ml vitamin E succinate, while at 3, 5, 7, and 10 microg/ml supplementary vitamin E succinate, free radical levels increased compared to the 1 microg/ml group, but not compared to control cultures. These results suggest that the inhibitory effects of vitamin E succinate on BL6-F10 cell growth in vitro is not a consequence of its antioxidant properties, but may, in fact, be due to one or more of its other potential roles within the cells, such as the regulation of cellular enzyme activities involved in growth.

Batch studies on the removal of gold(III) from aqueous solution by Azolla filiculoides

Azolla filiculoides removed 86% and 100% of gold(III) from initial metal solutions of 2–10 mg gold l−1 increasing with increased initial concentrations of gold(III). The biomass gave greater than 95% removal efficiency from solution at all biomass concentrations measured. Complete removal of gold occurred at pH 2, with 42% removal at pH 3 and 4, and 63% and 73% removal at pH 5 and 6, respectively. No temperature-dependence removal was observed.

Metal recovery from Saccharomyces cerevisiae biosorption columns

SummaryThe bioaccumulation of metal chlorides (Cu, Zn, Co, Cd, Ni and Cr) to immobilised S. cerevisiae was studied in packed-bed continuous flow columns. The metals were eluted from the columns using 0.1 M HCl, with a desorption of ≥ 90 % being attained. Reusability of the biomass was demonstrated. Mixed metal solutions were applied and selective binding and recovery was achieved between copper and cobalt.

Enhanced heavy metal removal from waste water by viable, glucose pretreated Saccharomyces cerevisiae cells

SummaryThe bioaccumulation of metals (Cu2+, Cr6+, Cd2+, Ni2+ and Zn2+) from three electroplating effluents by viable Saccharomyces cerevisiae, and the effect of glucose treatment on accumulation was determined. Pretreatment of the yeast cells with glucose increased the amount of metal removed, whilst direct addition of glucose to the yeast-effluent solution had no effect on the amount of metal accumulated.

Removal and recovery of nickel from aqueous solution and electroplating rinse effluent using Azolla filiculoides

Abstract The removal of nickel from aqueous solutions and electroplating rinse effluent by Azolla biomass in batch and column experiments was investigated. The maximum nickel uptake by Azolla in the batch at an optimum pH of 6·5 was found to be 43·4 mg g −1 . The dried Azolla filiculoides showed good mechanical stability with repeated column operations at extreme pHs. Nickel uptake in column operation before 60% saturation of the biomass was found to be between 21·6 and 27·9 mg g −1 with varying flow rates (from 16 ml h −1 g −1 to 160 ml h −1 g −1 ). Complete desorption of bound nickel was achieved with 120 ml of either 0·2 N H 2 SO 4 or HCl. This, together with the data from regeneration efficiency for five cycles, provided evidence that the reusabilities of Azolla in treatment of nickel-laden wastewater are viable. An effluent free, closed-loop nickel treatment system, with Azolla biomass as the sorbent, is proposed.

A continuous process for the biological treatment of heavy metal contaminated acid mine water

Abstract Alkaline precipitation of heavy metals from acidic water streams is a popular and long standing treatment process. While this process is efficient it requires the continuous addition of an alkaline material, such as lime. In the long term or when treating large volumes of effluent this process becomes expensive, with costs in the mining sector routinely exceeding millions of rands annually. The process described below utilises alkalinity generated by the alga Spirulina sp., in a continuous system to precipitate heavy metals. The design of the system separates the algal component from the metal containing stream to overcome metal toxicity. The primary treatment process consistently removed over 99% of the iron (98.9 mg/l) and between 80 and 95% of the zinc (7.16 mg/l) and lead (2.35 mg/l) over a 14-day period (20 l effluent treated). In addition the pH of the raw effluent was increased from 1.8 to over 7 in the post-treatment stream. Secondary treatment and polishing steps depend on the nature of the effluent treated. In the case of the high sulphate effluent the treated stream was passed into an anaerobic digester at a rate of 4 l/day. The combination of the primary and secondary treatments effected a removal of over 95% of all metals tested for as well as a 90% reduction in the sulphate load. The running cost of such a process would be low as the salinity and nutrient requirements for the algal culture could be provided by using tannery effluent or a combination of saline water and sewage. This would have the additional benefit of treating either a tannery or sewage effluent as part of an integrated process.

Influence of antioxidants on cadmium toxicity of mouse preimplantation embryos in vitro

To test the hypothesis that the developmental toxicity of cadmium (Cd) is due in part to oxidative damage, embryos were cultured in medium containing 0.0, 1.0, 3.0, or 6.0 microM Cd with or without various antioxidants for 72 h. Ascorbate, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and glutathione (GSH) were all effective at ameliorating 1.0 microM Cd-induced embryotoxicity. For embryos cultured in medium containing either 3.0 or 6.0 microM Cd, GSH was effective at ameliorating Cd toxicity while the other antioxidants tested were ineffective. Pretreating embryos with antioxidants for 24 h prior to exposing them to Cd and antioxidants did not significantly alter the previously observed improvement with the exception that pretreatment with GSH virtually eliminated Cd-induced embryotoxicity between 1.0 and 6.0 microM Cd. A 4-h exposure to GSH prior to culture in Cd markedly improved embryo development suggesting that GSH taken up during pretreatment can provide protection against Cd-induced embryotoxicity. This work supports the hypothesis that the developmental toxicity of Cd is in part due to oxidative damage that can be modulated by select antioxidants.

Removal of lead from solution by the non-viable biomass of the water fern Azolla filiculoides

Non-viable biomass of the aquatic fern, Azolla filiculoides, removed up to 93 mg lead/g biomass from solution. Lead removal varied from 30% of the initial lead concentration at pH 1.5 to approximately 95% at pH values of 3.5 and 4.5. Lead removal decreased to 30% of the initial lead concentration if the lead concentration was initially over 400 mg/l. Lead removal remained at approximately 90% between 10 °C and 50 °C. Biomass concentration (4–8 mg/l) had little effect on lead removal.

Cation loss during accumulation of heavy metal cations by Saccharomyces cerevisiae

SummaryCu2+ accumulation byS. cerevisiae resulted in rapid release of 70% of cellular K+, followed by a slower release of approximately 60% of cellular Mg2+, but little loss of Ca2+. Co2+ was accumulated in smaller quantities and caused a smaller loss of physiological cations than either Cu2+ or Cd2+. Mg2+ release during copper accumulation was maximal at pH 6. Mg2+ release during Cu2+ accumulation increased with temperature and salinity of the suspension.

Column sorption of Cr(VI) from electroplating effluent using formaldehyde cross-linked Saccharomyces cerevisiae

Pellets of Saccharomyces cerevisiae, cross-linked by 13% (w/v) formaldehyde, were used in fixed-bed columns to remove Cr(VI) from electroplating rinse effluent at varied influent pHs (2.5–7.5). The Cr uptake at 60% saturation of the biomass was 6.3 mg/g at an optimum pH of 2.5. Desorption of the bound metal was partially achieved by washing the column biomass with a combined solution of 1% (w/v) formaldehyde and 1 M HNO3.