Background and Objectives: Optimization of mazut biocracking with different variables is one of the bioengineering applications in petroleum industry. The purpose of this study was to optimize biocracking of mazut by native microorganisms.Materials and Methods: To optimize mazut cracking, using Taguchi method we run 32 experiments using seven factors including amount of microbial inoculation, initial pH, surfactant, glucose, phosphor source, nitrogen source and sea salt; each of them with four levels and factor of microorganism type with two levels for design of experiment using that 32 experiments were designed by them.Results: Results showed that microbial mixture, 0.016 OD600 microbial inoculations, pH 8.3, Tween80 concentration of 2 g/L, glucose concentration of 4 g/L, phosphate concentration of 5 g/L, ammonium concentration of 9 g/L and sea salt concentration of 0.5 g/L were optimized conditions for biocracking of mazut process.Conclusion: Optimized level for each factor was not essentially inevitably the highest or the lowest level. Based on the analysis of variance, phosphor source with 15.8% and pH with 14.8% had the highest effect among other factors; however overally, error factor with 31.6% had the highest influence. Amount of microbial inoculation with 0.63% had the lowest effect on optimizing biocracking of mazut.

Refineries are amongst the most energy-intensive and polluting industries in the world. Biotechnology may serve as an alternative low-cost and environmental-friendly tool to the current costly, toxic and hazardous refining processes. In this study, the compositional redistribution of a heavy hydrocarbon cut is investigated under biological conversion using native microbial consortia. The native consortia were obtained by batch enrichment method applied on oil-polluted soil samples from oil refineries of Iran. The bioconversion experiments were conducted with 20% and 40% (v/v) of the heavy cut as the sole carbon source and 10% (v/v) of the consortia broth in 250 ml flasks containing a mineral medium. The samples kept at 30°C stirring at 120 rpm for one week. The biotreated hydrocarbons were then separated and analyzed for determination of saturate, aromatic and resin fractions using column chromatography and gravimetric measurements. The results showed that the amounts of saturates increased by 6% to 92% while the resins decreased by 10% to 70% in most cases, compared to the blank. The GC-Mass analysis of the saturate fractions also revealed an increase in the cyclic and branched alkanes and a decrease in the S-containing and N-containing compounds.