35 research outputs found

    Salinity effects on biodegradation of Reactive Black 5 for one stage and two stages sequential anaerobic aerobic biological processes employing different anaerobic sludge

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    In this study the effect of NaCl, normally found in dye bath wastewaters employing reactive azo dyes, on the performance of sequential anaerobic-aerobic processes for treatment of Reactive Black 5 (RB5) containing media, with concentration in the range 100-500mgL-1, was investigated. Three possible scenarios of the sequential anaerobic-aerobic process, namely two stage process and one stage processes employing either anaerobic or activated sludge, were considered. The results showed a statistically significant enhancement of the anaerobic decolourisation efficiency as a result of the addition of 30gL-1 NaCl to the RB5 containing media for two stage processes and one stage processes employing anaerobic sludge. NaCl at 30gL-1 concentration also inhibited aerobic colour formation during two stage processes whereas it prevented aerobic decolourisation during one stage processes. HPLC and UV Vis analysis indicated that during anaerobic phase/stage the majority of azo bonds in RB5 molecules cleave whereas the hydrophobicity/MW of the resulting dye reduction metabolites decreases. The same analysis revealed partial mineralisation of RB5 reduction metabolites under aerobic conditions. The results of the present work also showed that the effect of salt on anaerobic decolourisation efficiency, TVFA and methane production was dependent on the exposure history of anaerobic sludge

    Adaptation of anaerobic biomass to saline conditions: Role of compatible solutes and extracellular polysaccharides

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    This study investigated the role of compatible solutes, extracellular polysaccharides (EPS), and nutrients on anaerobic biomass when stressed with salinity. When 1 mM of osmoregulants glycine betaine, α-glutamate and β-glutamate were added separately to serum bottles containing biomass not adapted to sodium, and fed with glucose and 35 g NaCl/L, all the compatible solutes were found to alleviate sodium inhibition, although glycine betaine was found to be the most effective. The effect of glycine betaine on different anaerobic bacterial groups under salinity stress was monitored using VFAs, and showed that methanogens were more protected than propionate utilisers. Moreover, the addition of 1 mM of glycine betaine to anaerobic biomass not adapted to salinity resulted in significantly higher methane production rates compared with anaerobic biomass that was exposed for 4 weeks to 35 g NaCl/L. Interestingly, under saline batch conditions when the medium was replaced totally the culture produced less methane than when only new substrate was added due to compatible solutes cycling between the media and the cell. The elimination of macronutrients from the medium was found to have a more pronounced negative effect on biomass under saline compared with nonsaline conditions, and because of the synthesis of N-compatible solutes sufficient nutrients should always be present. On the other hand, the absence from the medium of micronutrients did not further reduce biomass activity under salinity. Finally, a higher production of EPS was obtained from biomass exposed to higher salt concentrations, and its composition was found to change under different saline conditions and time. As a result, biomass under saline conditions had a slightly higher mean flock size compared with the biomass that was not subjected to salt. © 2008 Elsevier Inc. All rights reserved

    Post-treatment of a submerged anaerobic membrane bioreactor (SAMBR) saline effluent using powdered activated carbon (PAC)

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    Powdered activated carbon (PAC) was added to an effluent from a submerged anaerobic membrane bioreactor (SAMBR) treating saline wastewater as a post-treatment method. The adsorption of contaminants was carried out and key Freundlich isotherm parameters were evaluated. The results showed a reduction in dissolved organic carbon (DOC) in the effluent of over 80% after treatment with 1.7 g PAC/L. The composition of the effluent was determined by the use of size exclusion chromatography (SEC) and by GC–MS analysis. Most of the components of the effluent had a MW less than 1 kDa, and these were the hardest to eliminate by PAC adsorption. m-Aminophenylacetylene, cyclohexane 1,2,4 trimethyl and cholestan 3-one were found in the effluent, but could be removed by PAC adsorption. Finally, different methods for using PAC, with or without biomass, revealed that aerobic biomass enhanced the adsorption process resulting in higher DOC removals

    Integrated chemical and biochemical technology to produce biogas with a reduced ammonia content from municipal biowaste. Validating lab-scale research in a real operational environment

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    The current paper reports the scientific, technical, environmental, economic and social impacts of two integrated chemical and biochemical processes that employed a novel virtuous biowaste cycle under real operational conditions of three industrial sites in Italy, Greece and Cyprus. The work was based on previous laboratory research pertinent to the valorisation of municipal biowastes (MBWs) as a feedstock to obtain value added soluble biobased (SBO) products. The research pointed out that the site-specific nature of MBW was the main criticality, which could potentially hinder the industrialisation of the MBW-SBO paradigm. The present work demonstrates the feasibility of a new scenario for a conventional waste treatment plan collecting and processing MBWs by anaerobic and aerobic fermentation. In essence, the virtuous biowaste cycle is realised by producing SBO from the plant MBW (process 1) and recirculating it to the MBW feed of the anaerobic fermentation reactor to reduce the ammonia content in the digestate (process 2). This mitigates the digestate's environmental impact. Life cycle sustainability assessment demonstrates that the use of SBO produced from local MBW allowed reducing the ammonia content of the digestate generated from the local anaerobic fermentation facilities in the three different countries by 21–68% as well its eutrophication potential. Process 2 allowed at least 86% OPEX cost saving compared to conventional digestate post-treatment technologies for ammonia abatement, while paying off the CAPEX cost in less than one year. Socio-economic analysis evaluated the impacts on workers and local community stakeholders, potentially stemming from the implementation of processes 1 and 2 at European level. The analysis of SBO composition and performances in each operational site investigated showed that improved performance of process 2 might be achieved by isolating the active principles in raw SBO prior to their use in process 2. Chemical and biochemical catalysis by SBO active principles in process 2 support the specific perspective

    The function of ORAOV1/LTO1, a gene that is overexpressed frequently in cancer: essential roles in the function and biogenesis of the ribosome

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    ORAOV1 (oral cancer overexpressed) is overexpressed in many solid tumours, making a key contribution to the development of cancer, but the cellular role of ORAOV1 is unknown. The yeast orthologue of this protein is encoded by the hitherto uncharacterized essential gene, YNL260c. Expression of ORAOV1 restores viability to yeast cells lacking YNL260c. Under nonpermissive conditions, our conditional mutants of YNL260c are defective in the maturation of the 60S ribosomal subunit, whereas maturation of the 40S subunit is unaffected. Also, initiation of translation is abrogated when YNL260c function is lost. YNL260c is indispensible for life in oxygen, but is nonessential under anaerobic conditions. Consequently, the toxic affects of aerobic metabolism on biogenesis and function of the ribosome are alleviated by YNL260c, hence, we rename YNL260c as LTO1; required for biogenesis of the large ribosomal subunit and initiation of translation in oxygen. Lto1 is found in a complex with Rli1/ABCE1, an ATP-binding cassette (ABC)-ATPase bearing N-terminal [4Fe - 4S] clusters. Like Lto1, the Rli1/ABCE1 [4Fe - 4S] clusters are not required for viability under anaerobic conditions, but are essential in the presence of oxygen. Loss of Lto1 function renders cells susceptible to hydroperoxide pro-oxidants, though this type of sensitivity is specific to certain types of oxidative stress as the lto1 mutants are not sensitive to an agent that oxidizes thiols. These findings reflect a functional interaction between Lto1 and the Rli1/ABCE1 [4Fe - 4S] clusters, as part of a complex, which relieves the toxic effects of reactive oxygen species (ROS) on biogenesis and function of the ribosome. This complex also includes Yae1, which bridges the interaction between Lto1 and Rli1/ABCE1. Interactions between members of this complex were demonstrated both in vivo and in vitro. An increased generation of ROS is a feature shared by many cancers. The ORAOV1 complex could prevent ROS-induced ribosomal damage, explaining why overexpression of ORAOV1 is so common in solid tumours.ORAOV1 (oral cancer overexpressed) is overexpressed in many solid tumours, making a key contribution to the development of cancer, but the cellular role of ORAOV1 is unknown. The yeast orthologue of this protein is encoded by the hitherto uncharacterized essential gene, YNL260c. Expression of ORAOV1 restores viability to yeast cells lacking YNL260c. Under nonpermissive conditions, our conditional mutants of YNL260c are defective in the maturation of the 60S ribosomal subunit, whereas maturation of the 40S subunit is unaffected. Also, initiation of translation is abrogated when YNL260c function is lost. YNL260c is indispensible for life in oxygen, but is nonessential under anaerobic conditions. Consequently, the toxic affects of aerobic metabolism on biogenesis and function of the ribosome are alleviated by YNL260c, hence, we rename YNL260c as LTO1; required for biogenesis of the large ribosomal subunit and initiation of translation in oxygen. Lto1 is found in a complex with Rli1/ABCE1, an ATP-binding cassette (ABC)-ATPase bearing N-terminal [4Fe - 4S] clusters. Like Lto1, the Rli1/ABCE1 [4Fe - 4S] clusters are not required for viability under anaerobic conditions, but are essential in the presence of oxygen. Loss of Lto1 function renders cells susceptible to hydroperoxide pro-oxidants, though this type of sensitivity is specific to certain types of oxidative stress as the lto1 mutants are not sensitive to an agent that oxidizes thiols. These findings reflect a functional interaction between Lto1 and the Rli1/ABCE1 [4Fe - 4S] clusters, as part of a complex, which relieves the toxic effects of reactive oxygen species (ROS) on biogenesis and function of the ribosome. This complex also includes Yae1, which bridges the interaction between Lto1 and Rli1/ABCE1. Interactions between members of this complex were demonstrated both in vivo and in vitro. An increased generation of ROS is a feature shared by many cancers. The ORAOV1 complex could prevent ROS-induced ribosomal damage, explaining why overexpression of ORAOV1 is so common in solid tumours
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