The microbial degradation of the saturated and sulfur aromatic fractions of a heavy oil was examined in aerobic aqueous conditions employing a pure culture of a Pseudomonas sp. in the presence of natural and synthetic sorbents. All three natural sorbents tested (keratin, chitosan and chitin) were capable of adsorbing large amounts of heavy oil as well as enormously increasing the n-alkane biodegradation rate and decreasing the lag phase by up to five-seven times as much as that in the absence of sorbents. In the presence of natural sorbents n-alkane biodegradation was complete after 7 days while in their absence the same result took 40 days. This time decrease was ascribed to an improved interaction between the oil and the microorganisms derived from the formation of a water/cell/oil/sorbent interphase. The values of the accelerating conversion factor, b, and the length of the lag phase, 1/ab, were determined for the different sorbents using a mathematical expression, and they could represent two important parameters for the description of n-alkane biodegradation kinetics.