Hydrocarbon-utilizing microorganisms naturally associated with sawdust

Sawdust, one of the materials used as sorbent for removing spilled oil from polluted environments was naturally colonized by hydrocarbon-utilizing fungi, 1 x 10(5)-2 x 10(5) colony forming units (CFU) g(-1), depending on the hydrocarbon substrate. This sorbent was initially free of hydrocarbon-utilizing bacteria. Incubating wet sawdust at 30 degrees C resulted in gradually increasing the fungal counts to reach after 6 months between 5 x 10(6) and 7 x 10(6) CFU g(-1), and the appearance of hydrocarbon-utilizing bacteria in numbers between 8 x 10(4) and 3 x 10(5) cells g(-1). The fungi belonged to the genera Candida (32% of the total), Penicillium (21%), Aspergillus (15%), Rhizopus (12%), Cladosporium (9%), Mucor (7%) and Fusarium (4%). Based on their 16S rRNA gene sequences the bacteria were affiliated to Actinobacterium sp. (38%). Micrococcus luteus (30%), Rhodococcus erythropolis, (19%) and Rhodococcus opacus (13%). Individual pure fungal and bacterial isolates grew on a wide range of individual pure aliphatic (n-alkanes with chain lengths between C-9 and C-40) and aromatic (benzene, biphenyl, anthracene, naphthalene and phenanthrene) hydrocarbons as sole sources of carbon and energy. Quantitative determinations revealed that all fungal and bacterial isolates could consume considerable proportions of crude oil, phenanthrene (an aromatic hydrocarbon) and n-hexadecane (an aliphatic hydrocarbon) in batch cultures. It was concluded that when sawdust is used as a sorbent, the associated microorganisms probably contribute to the bioremediation of oil and hydrocarbon pollutants in the environment. (C) 2011 Elsevier Ltd. All rights reserved.