Profiling of Indigenous Microbial Community Dynamics and Metabolic Activity During Enrichment in Molasses-Supplemented Crude Oil-Brine Mixtures for Improved Understanding of Microbial Enhanced Oil Recovery.

Anaerobic incubations using crude oil and brine from a North Sea reservoir were conducted to gain increased understanding of indigenous microbial community development, metabolite production, and the effects on the oil-brine system after addition of a complex carbon source, molasses, with or without nitrate to boost microbial growth. Growth of the indigenous microbes was stimulated by addition of molasses. Pyrosequencing showed that specifically Anaerobaculum, Petrotoga, and Methanothermococcus were enriched. Addition of nitrate favored the growth of Petrotoga over Anaerobaculum. The microbial growth caused changes in the crude oil-brine system: formation of oil emulsions, and reduction of interfacial tension (IFT). Reduction in IFT was associated with microbes being present at the oil-brine interphase. These findings suggest that stimulation of indigenous microbial growth by addition of molasses has potential as microbial enhanced oil recovery (MEOR) strategy in North Sea oil reservoirs.

Molecular and biochemical characterization of the thermoactive family 1 pectate lyase from the hyperthermophilic bacterium Thermotoga maritima.

The ability of the hyperthermophilic bacterium Thermotoga maritima to grow on pectin as a sole carbon source coincides with the secretion of a pectate lyase A (PelA) in the extracellular medium. The pel A gene of T. maritima was functionally expressed in Escherichia coli as the first heterologously produced thermophilic pectinase, and purified to homogeneity. Gel filtration indicated that the native form of PelA is tetrameric. Highest activity (422 units/mg, with a K(m) of 0.06 mM) was demonstrated on polygalacturonic acid (PGA), whereas pectins with an increasing degree of methylation were degraded at a decreasing rate. In the tradition of pectate lyases, PelA demonstrated full dependency on Ca(2+) for stability and activity. The enzyme is highly thermoactive and thermostable, operating optimally at 90 degrees C and pH 9.0, with a half-life for thermal inactivation of almost 2 h at 95 degrees C, and an apparent melting temperature of 102.5 degrees C. Detailed characterization of the product formation with PGA indicated that PelA has a unique eliminative exo-cleavage pattern liberating unsaturated trigalacturonate as the major product, in contrast with unsaturated digalacturonate for other exopectate lyases known. The unique exo-acting mode of action was supported by progression profiles of PelA on oligogalacturonides (degree of polymerization, 3-8) and the examination of the bond cleavage frequencies.