Production of uracil from methane by a newly isolated Methylomonas sp. SW1.

Methane is an abundant, inexpensive one-carbon feedstock and one of the most powerful greenhouse gases. Because it does not compete with food demand, it is considered a promising carbon feedstock for the production of valuable products using methanotrophic bacteria. Here, we isolated a novel methanotrophic bacterium, Methylomonas sp. SW1, from a sewage sample obtained from Wonju City Water Supply Drainage Center, Republic of Korea. The conditions for uracil production by Methylomonas sp. SW1, such as Cu2+ concentration and temperature were investigated and optimized. As a result, Methylomonas sp. SW1 produced uracil from methane as a sole carbon source with a titer of 2.1mg/L in 84h without genetic engineering under the optimized condition. The results in this study demonstrate the feasibility of using Methylomonas sp. SW1 for the production of uracil from methane. This is the first report of uracil production from gas feedstock by methanotrophic bacteria.

Effect of pH on the metabolic flux of Klebsiella oxytoca producing 2,3-butanediol in continuous cultures at different dilution rates.

The efficiency of the bioconversion process and the achievable end-product concentration decides the economic feasibility of microbial 2,3-butanediol (2,3-BDO) production. In 2,3-BDO production, optimization of culture condition is required for cell growth and metabolism. Also, the pH is an important factor that influences microbial performance. For different microorganisms and substrates, it has been shown that the distribution of the metabolites in 2,3-BDO fermentation is greatly affected by pH, and the optimum pH for 2,3-BDO production seems dependently linked to the particular strain and the substrate employed. Quantification analysis of intracellular metabolites and metabolic flux analysis (MFA) were used to investigate the effect of pH on the Klebsiella oxytoca producing 2,3-BDO and other organic acids. The main objectives of MFA are the estimation of intracellular metabolic fluxes and the identification of rate-limiting step and the key enzymes. This study was conducted under continuous aerobic conditions at different dilution rates (0.1, 0.2, and 0.3 h(-1)) and different pH values (pH 5.5 and 7.0) for the steady-state experimental data. In order to obtain the flux distribution, the extracellular specific rates were calculated from the experimental data using the metabolic network model of K. oxytoca. Intracellular metabolite concentration profiles were generated using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry.

Metabolic profiling of Klebsiella oxytoca: evaluation of methods for extraction of intracellular metabolites using UPLC/Q-TOF-MS.

The global pool of intracellular metabolites is a reflection of all the metabolic functions of an organism. In the absence of in situ methods capable of directly measuring metabolite pools, intracellular metabolite measurements need to be performed after an extraction procedure. In this study, we evaluated the optimization of technologies for generation of a global metabolomics profile for intracellular metabolites in Klebsiella oxytoca. Intracellular metabolites of K. oxytoca were extracted at the early stationary phase using six different common extraction procedures, including cold methanol, boiling ethanol, methanol/chloroform combinations, hot water, potassium hydroxide, and perchloric acid. The metabolites were subsequently collected for further analysis, and intracellular metabolite concentration profiles were generated using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry. During analysis, the stability of metabolites extracted using cold methanol was clearly higher than that obtained by other extraction methods. For the majority of metabolites, extracts generated in this manner exhibited the greatest recovery, with high reproducibility. Therefore, the use of cold ethanol was the best extraction method for attaining a metabolic profile. However, in another parallel extraction method, perchloric acid may also be required to maximize the range of metabolites recovered, particularly to extract glucose 1-phosphate and NADPH.