Two-phase partitioning bioreactors operating with polymers applied to the removal of substituted phenols.
ABSTRACT Significant improvement in biodegradation performance has been demonstrated arising from the reduction of cytotoxicity provided by the sequestering of 4-nitrophenol (4NP) within Hytrel polymer beads added to a two-phase partitioning bioreactor (TPPB) operating in sequencing batch reactor (SBR) mode. This reduced toxicity is particularly apparent as the feed substrate concentration is increased; in fact it was shown that at a feed of 1000 mg/L 4NP, the inhibitory effect of the substrate completely prevents degradation from occurring in a single-phase system, whereas at only a 5% polymer loading, rapid and compete biodegradation is achieved. Different polymer/aqueous phase ratios were used to detoxify varying feed concentrations, and degradation rates were enhanced through the use of increased polymer loadings. As demonstrated in oxygen uptake experiments, the addition of polymers also reduces the maximum demand for oxygen, relative to single-phase operation, and smoothes the demand for oxygen throughout the degradation process. Polymer regeneration has also been further characterized by quantifying the number of methanol washes required to achieve satisfactory 4NP residuals, and the addition of a small amount of cosolvent has been shown to dramatically increase the rate of bioregeneration to produce beads ready for reuse.
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ABSTRACT: The molecular pathogenesis of hepatocellular carcinoma is well-studied but not completely understood. We utilized a microcell-hybrid model of tumor suppression in rat liver tumor cells to facilitate the identification of liver tumor suppressor genes located on human chromosome 11. These investigations confirmed a liver tumor suppressor locus at human 11p11.2, identified Wt1 as a potential effector of 11p11.2-mediated tumor suppression, and subsequently identified human SYT13 as a strong candidate for the 11p11.2 liver tumor suppressor gene. In the studies presented here, we introduced SYT13 into the GN6TF rat liver tumor cell line to characterize a functional role for SYT13 in this model system. Transfected clones expressing an SDS-resistant dimer form of the SYT13 protein displayed induction of Wt1 gene expression and a significant attenuation of the neoplastic phenotype exhibited by the parental tumor cell line. Saturation densities and anchorage-independent growth of SYT13 dimer-positive cell lines were reduced in vitro, and tumorigenicity was significantly decreased or ablated in syngeneic host rats in vivo. In addition, restoration of the contact-inhibited, epithelioid morphology observed in normal liver epithelial cells accompanied ectopic expression of the SYT13 protein dimer, suggesting that SYT13 may be mediating an epithelial differentiation coordinate with tumor suppression in these cells. Accordingly, the expression of E-cadherin (Cdh1) mRNA was increased >100-fold in SYT13-dimer-positive cell lines and the Cdh1 transcriptional repressor Snail was decreased >3-fold in these cells compared to the parental tumor cells. These studies combine to suggest that SYT13 is a liver tumor suppressor gene and that its function may be mediated through pathways implicated in mesenchymal to epithelial transition.Experimental and Molecular Pathology 12/2010; 89(3):209-16. · 2.13 Impact Factor
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ABSTRACT: The biological treatment of phenolics is constrained by the inherent cytotoxicity of these compounds. One method to alleviate such toxicity is to add a sequestering phase to absorb, and subsequently release, the substrate(s) to the micro-organisms; such a system is termed a Two Phase Partitioning Bioreactor. Here we have compared the performance of a TPPB, relative to single phase operation, in which a small volume (5%, v/v) of beads of the polymer Hytrel 8206 was used to treat aqueous mixtures of 2,4-dimethylphenol and 4-nitrophenol. Hytrel 8206 was selected from a range of polymers that were tested for their partition coefficients (PCs) for the target molecules, with the more hydrophobic compound (2,4-dimethylphenol) having a higher PC value (201) than 4-nitrophenol (143). Significantly increased removal rates for both substrates were demonstrated in TPPB mode relative to single phase operation. Additionally, the differential release of the compounds to the aqueous phase and their distinct PC values changed the kinetic pattern of the biotreatment system, smoothing out the cellular oxygen demand. Release of the substrates by the polymer over 60 operating cycles was virtually complete (>97%) demonstrating the reusability and robustness of the use of polymers in overcoming cytotoxicity of phenolic substrates.Journal of hazardous materials 07/2011; 191(1-3):190-5. · 4.14 Impact Factor
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ABSTRACT: The biological removal of monoaromatic compounds from contaminated environments, usually arising from industrial activity, is challenging because of the inherent toxicity of these compounds to microorganisms, particularly at the concentrations that can be encountered in industrial waste streams. A wide range of bioprocess designs have been proposed and tested with the aim of achieving high removal efficiencies, with varying degrees of technical success, and potential for practical implementation. This review reports on the progress on variations of well-known themes made in the last 3-4 years, as well as new bioprocess technologies that address the cytotoxicity of monoaromatics directly. Areas for further research are also proposed.Applied Microbiology and Biotechnology 06/2011; 90(5):1589-608. · 3.69 Impact Factor