Mineral Salt Medium (mineral + salt_medium)

Distribution by Scientific Domains

Selected Abstracts

Identity of active methanotrophs in landfill cover soil as revealed by DNA-stable isotope probing

Aurélie Cébron
Abstract A considerable amount of methane produced during decomposition of landfill waste can be oxidized in landfill cover soil by methane-oxidizing bacteria (methanotrophs) thus reducing greenhouse gas emissions to the atmosphere. The identity of active methanotrophs in Roscommon landfill cover soil, a slightly acidic peat soil, was assessed by DNA-stable isotope probing (SIP). Landfill cover soil slurries were incubated with 13C-labelled methane and under either nutrient-rich nitrate mineral salt medium or water. The identity of active methanotrophs was revealed by analysis of 13C-labelled DNA fractions. The diversity of functional genes (pmoA and mmoX) and 16S rRNA genes was analyzed using clone libraries, microarrays and denaturing gradient gel electrophoresis. 16S rRNA gene analysis revealed that the cover soil was mainly dominated by Type II methanotrophs closely related to the genera Methylocella and Methylocapsa and to Methylocystis species. These results were supported by analysis of mmoX genes in 13C-DNA. Analysis of pmoA gene diversity indicated that a significant proportion of active bacteria were also closely related to the Type I methanotrophs, Methylobacter and Methylomonas species. Environmental conditions in the slightly acidic peat soil from Roscommon landfill cover allow establishment of both Type I and Type II methanotrophs. [source]

Hydrocarbon degradation by thermophilic Nocardia otitidiscaviarum strain TSH1: physiological aspects

Majid Zeinali
Abstract Indigenous thermophilic hydrocarbon degraders are of special significance for the bioremediation of oil-contaminated desert soils with ambient temperature of 45,50 °C. The first objective of this study was to demonstrate the hydrocarbon-degrading capability of Nocardia otitidiscaviarum TSH1 (DSM 45036) which grows optimally at 50 °C. Analysis of the metabolic profile of the strain TSH1 showed that it could metabolize phenol, intermediate-chain-length n -alkanes and some polycyclic aromatic hydrocarbons (PAHs) ranging in size from two to four fused rings efficiently, but not toluene and xylene. N. otitidiscaviarum TSH1 was able to survive and grow at phenol concentrations up to 875 mg l,1. For the first time, the physiological response of a thermophilic Nocardia strain to poorly available hydrophobic compounds was also investigated. When grown on a mineral salt medium with hexadecane, N. otitidiscaviarum TSH1 showed very high affinity for the organic phase. Additionally, PAH-grown cells were considerably hydrophobic. The capacity of PAH-utilizing N. otitidiscaviarum TSH1 isolate to produce biosurfactants was also investigated. Fatty acids (C14,C18) were detected by GC-MS analysis during bacterial growth in PAH supplemented mineral media. High cell surface hydrophobicity and capability of N. otitidiscaviarum TSH1 to degrade different hydrocarbons at 50 °C may make it an ideal candidate to treat oil-contaminated desert soils. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Decolorisation of a monoazo disperse dye with Candida tropicalis

Sucharita Arora
Decolorisation of a heterocyclic monoazo disperse dye by the yeast species Candida tropicalis growing in mineral salt medium has been investigated. The effects of nutritional as well as environmental factors on the decolorisation efficiency were studied. Though Candida tropicalis displayed good growth in aerobic conditions, the colour removal was best under anoxic conditions. The degradation products of the decolorisation experiments under aerobic, as well as anoxic, conditions have also been identified. [source]

Metabolic engineering of Escherichia coli for the production of putrescine: A four carbon diamine

Zhi-Gang Qian
Abstract A four carbon linear chain diamine, putrescine (1,4-diaminobutane), is an important platform chemical having a wide range of applications in chemical industry. Biotechnological production of putrescine from renewable feedstock is a promising alternative to the chemical synthesis that originates from non-renewable petroleum. Here we report development of a metabolically engineered strain of Escherichia coli that produces putrescine at high titer in glucose mineral salts medium. First, a base strain was constructed by inactivating the putrescine degradation and utilization pathways, and deleting the ornithine carbamoyltransferase chain I gene argI to make more precursors available for putrescine synthesis. Next, ornithine decarboxylase, which converts ornithine to putrescine, was amplified by a combination of plasmid-based and chromosome-based overexpression of the coding genes under the strong tac or trc promoter. Furthermore, the ornithine biosynthetic genes (argC-E) were overexpressed from the trc promoter, which replaced the native promoter in the genome, to increase the ornithine pool. Finally, strain performance was further improved by the deletion of the stress responsive RNA polymerase sigma factor RpoS, a well-known global transcription regulator that controls the expression of ca. 10% of the E. coli genes. The final engineered E. coli strain was able to produce 1.68,g,L,1 of putrescine with a yield of 0.168,g,g,1 glucose. Furthermore, high cell density cultivation allowed production of 24.2,g,L,1 of putrescine with a productivity of 0.75,g,L,1,h,1. The strategy reported here should be useful for the bio-based production of putrescine from renewable resources, and also for the development of strains capable of producing other diamines, which are important as nitrogen-containing platform chemicals. Biotechnol. Bioeng. 2009; 104: 651,662 © 2009 Wiley Periodicals, Inc. [source]