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Item type:Publication, Access status: without files , Lipopeptide biosurfactant production by chitosan-immobilized Bacillus sp. GY19 and their recovery by foam fractionation(Elsevier, 2014-09-28); ; ; ; Bacillus sp. GY19 was immobilized on chitosan to increase cell density and facilitate lipopeptide production. Palm oil was added to a waste glycerol based medium as precursor for the lipopeptides. The immobilized cells could be reused in stirred tank fermenter for at least 6 cycles with an optimal condition of 80. g/L immobilized cells, 10% (v/v) waste glycerol and 1.25% (v/v) palm oil. The highest lipopeptide concentration observed during the steady state was 7.12. g/L. The presence of chitosan in the fermenter reduced foaming problems due to its absorption property, which could interrupt the aggregation of air bubble and lipopeptides. The lipopeptides were separated and purified from the culture medium by a simple design foam fractionation unit. The amounts of lipopeptides in foamate produced from palm oil and crude palm oil added culture media were 10.9 and 9.8. g/L, respectively. HPLC profile of lipopeptide extracted from the foamate had less impurity peaks than that from the culture medium. Both foamate samples showed 100% oil displacement efficiency with diesel oil, followed by Arabian light oil and heavy oil. It is thus possible to apply the sequential lipopeptide production and recovery process for producing a ready-to-use foamate for petroleum remediation.Publicationtype: Journal Article53 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Cometabolism of trichloroethylene : concepts, limitations and available strategies for sustained biodegradationDue to its toxicity and persistence in the environment, trichloroethylene (TCE) has become a major soil and groundwater contaminant in many countries. A group of aliphatic- and aromatic-degrading bacteria expressing nonspecific oxygenases have been reported to transform TCE through aerobic cometabolism in the presence of primary substrate such as methane, ammonia, propane, phenol, toluene or cumene. This paper reviews the fundamentals and results of TCE cometabolism from laboratory and field studies. The limitations associated with TCE cometabolism including the causes and effects of substrate and/or inducer utilization rate and depletion, enzyme inhibition and inactivation, and cytotoxicity during TCE oxidation among various TCE-degrading bacteria and enzymes are discussed. In addition, the potential strategies e. g. addition of primary substrate/inducer or external energy substrate, use of a two-stage reactor and application of cell immobilization for sustained TCE degradation are highlighted. The review summarizes important information on TCE cometabolism, which is necessary for developing efficient TCE bioremediation approaches.Publicationtype: Journal Article32 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Cometabolic degradation of trichloroethene by rhodococcus sp. strain L4 immobilized on plant materials rich in essential oilsThe cometabolic degradation of trichloroethene (TCE) by Rhodococcus sp. L4 was limited by the loss of enzyme activity during TCE transformation. This problem was overcome by repeated addition of inducing substrates, such as cumene, limonene, or cumin aldehyde, to the cells. Alternatively, Rhodococcus sp. L4 was immobilized on plant materials which contain those inducers In their essential oils. Cumin seeds were the most suitable immobilizing material, and the immobilized cells tolerated up to 68 μM TCE and degraded TCE continuously. The activity of Immobilized cells, which had been inactivated partially during TCE degradation, could be reactivated by incubation in mineral salts medium without TCE. These findings demonstrate that immobilization of Rhodococcus sp. L4 on plant materials rich in essential oils is a promising method for efficient cometabolic degradation of TCE.Publicationtype: Journal Article101