Microbial threats to aviation fuels: susceptibility and biostability studies

Biodegradation of aviation fuels remains a critical factor during storage and operation, affecting both the composition and performance properties of kerosene fractions. This study aims to establish the relationship between the component composition of modern jet fuels and their biostability. In addition, the effect of typical additives was evaluated. Four industrially used kerosene fractions differing in refining depth were investigated-straight-run, hydrodemercaptanized, hydrotreated, and hydrocracked-along with their mixtures containing antioxidant (Agidol-1) and lubricity additive (Unicor J). Biological tests were conducted under standardized conditions (IP 385/ASTM D6974; GOST 9.023) using Amorphotheca resinae as the test organism; changes in group hydrocarbon composition were analyzed by GC × GC-MS. It was found that susceptibility to biodegradation decreases with increasing refining depth, while microbial activity consistently resulted in a reduction in paraffinic and naphthenic hydrocarbons and a relative increase in aromatics; simultaneously, sulfur content decreases. Paradoxically, the most pronounced increases in acidity and existent gum content were observed in the hydrotreated and hydrocracked fractions. Agidol-1 exhibited biostatic (antimicrobial) activity, but was accompanied by a marked drop in aqueous phase pH (≈ 4), suggesting increased corrosion risk associated with the aqueous phase. Unicor J produced a slight positive effect, likely due to its surface-active properties.