Steel Corrosion Induced by Gluconacetobacter sp. in Diesel Fuel Sludge

The corrosion of diesel fuel storage tanks in the US was first reported in 2007, when the transition to more sustainable fuels, such as E10 and biodiesel, was underway, along with the adoption of ultra-low-sulfur diesel. Corrosion is caused by acetic acid produced by contaminating bacteria in fuel storage tanks. This study aimed to investigate the relationship between fuel improvements and microbiologically influenced corrosion in diesel fuel storage tanks by isolating acetic acid-producing bacteria and examining their effects on the deterioration of diesel-related fuels. The results revealed that the bacterium isolated from the two samples was Gluconacetobacter sp. (named as strain US-001). Among the carbon sources tested relevant to recent fuels, ethanol was dissimilated with acetic acid production and decreasing pH. Furthermore, the presence of 0.5% ethanol enabled the deterioration of n-dodecane, although it did not affect the pH. Dibenzothiophene, among the tested sulfur compounds present in previous low-sulfur diesel, inhibited the growth of the isolated strain US-001. In a sealed cup with a limited oxygen supply, the culture of strain US-001 experimentally induced severe steel corrosion when ethanol/n-dodecane was used as the carbon source. In conclusion, we speculate that ethanol contamination through E10 gasoline in diesel fuel tanks facilitates the growth of acetic acid bacteria, leading to the accumulation of acetic acid and a decrease in the pH of the sludge. Simultaneously, the introduction of ultra-low-sulfur diesel created more favorable growth conditions by removing their growth inhibitors, thereby resulting in microbiologically influenced corrosion of diesel fuel storage tanks.