Fast biodegradation of long chain n-alkanes and crude oil at high concentrations with Rhodococcus sp. Moj-3449

Biodegradation of long chain n-alkanes and crude oil with fast rate and high concentration are desirable for bioremediation, especially in heavily oil-polluted areas, and enhanced oil recovery. We discovered Rhodococcus sp. Moj-3449 with such unique abilities by screening microorganisms for the growth on n-hexadecane at 30 mg/mL. The new strain grew very fast on 120 mg/mL of n-hexadecane giving a cell density of 14.7 g cdw/L after only 2 days’ incubation. During the growth with this strain, the oil–water phases were rapidly emulsified, giving rise to tolerance to high alkane concentration (250 mg/mL) and fast growth rate of 0.10–0.20 h−1 for alkane concentration of 1–180 mg/mL. The degraded concentration of n-hexadecane increased linearly with the initial alkane concentration (1–250 mg/mL). Incubation on n-hexadecane at 250 mg/mL for 7 days gave a cell density of 13.5 g cdw/L and degraded 124 mg/mL of n-hexadecane. The strain grew also fast on n-dodecane (C12), n-tetradecane (C14), and n-octadecane (C18), with degradation preference of C14 (=C16) > C12 > C18. Different from many alkane-degrading strains, Rhodococcus sp. Moj-3449 was found to have subterminal oxidation pathway. Rhodococcus sp. Moj-3449 degraded also crude oil fast at 60–250 mg/mL, with a wide range of n-alkanes (C10–C35) as substrates in which C14–C19 are preferred. The degradation ability increased with initial oil concentration from 60 to 150 mg/mL and slightly decreased afterwards. Incubation on 150 mg/mL of crude oil for 7 days degraded 37% of n-alkanes. The outstanding ability of rapidly degrading long chain n-alkanes and crude oil at high concentration makes Rhodococcus sp. Moj-3449 potentially useful for bioremediation and microbial enhanced oil recovery.