Real-time PCR Applied to Quantification of SRB in Bottom Water from Fuel Tanks

摘要

Microorganisms can grow in different types of fuels. The presence of water in the fuel is crucial for thegrowth of bacteria, fungi and yeasts. Microorganisms may grow in the presence of oxygen (aerobic) orin its absence (anaerobic), feeding primarily on hydrocarbon fuel, minerals and other impurities in thewater. The amount of water required for microbial growth is very small. A fuel containing only 1% ofwater presents favorable conditions for the development of microbial colonies and spores can survive inthe presence of only 5 -80 ppm of water. In practice, the bottoms of storage tanks of fuel or even tanksof buses and trucks have enough water for microbial growth. Microbial growth results in the productionof biomass (fouling), which is deposited at the bottom of the tank. Moreover, the microbial oxidation ofhydrocarbons produces corrosive metabolites, such as organic and inorganic acids. Biomass,metabolic products and corrosion products result in problems such as filter and pipelines clogging,production of emulsion, change in fuel quality and corrosion of metal tanks. The detection andquantification of microorganisms in industrial samples are traditionally based on culture techniquessuch as the most probable number (MPN) and colony forming units (CFU). However, the slow growth ofstrictly anaerobic sulfate-reducing bacteria (SRB) complicates the detection and isolation of thesemicroorganisms in culture media. The cultivation of SRB requires a long incubation period (28 days) toobtain the results. In some cases, the extended time for the detection of microorganisms retards the preventive and corrective actions which aggravate the corrosive process. In this work, the results ofSRB quantification in bottom water from fuel tanks analyzed by real-time PCR are shown.