Physiological versatility of Rhodococcus sp. 602 to synthesize triacylglycerols in different conditions

SILVA RA; GROSSI V; ROST E; ALVAREZ HM

Rosario Argentina

Congreso; V Congreso Argentino de Microbiologia General (SAMIGE); 2008

Sociedad Argentina de Microbiología General

A challenge in biotechnological approaches is the selection of the correct microorganism. Rhodococcus sp. 602 is a microorganism isolated from a soil sample collected in a polluted area from the petroleum industry. This is an oleaginous strain with the ability to degrade a broad variety of pollutants. The aim of this study was to test the physiological versatility of strain 602 to transform several substrates in triacylglycerols (TAG) in different culture conditions. First, we studied the ability of this strain to produce TAG from different substrates; strain 602 synthesized TAG from gluconate, benzoate, n-hexadecane, 3-cyclohexylpropionic acid, octadecylamine, ethanol + glycerol, n-hexadecane + n-hexadecanol and naphthalene; but not from phenanthrene, anthracene nor fluorene. Second, we quantified TAG produced from some of these substrates. From gluconate or benzoate TAG reached 71,22 or 64,91% of cellular dry weight, respectively. When this strain was cultivated on naphthalene under nitrogen limiting conditions, TAG reached 48,8 % of total lipids and was constituted by fatty acids of C8, C10 and C12 chain length; which are shorter than those occurring in gluconate or n-hexadecane cultures (C14 to C18). In this work we propose a new pathway for degradation of naphthalene in Rhodococcus, where a mono-oxigenase would be involved: naphthalene ¡æ 1-naphthol ¡æ 1,2,3,4-tetrahydro-1-hydroxynaphthalene ¡æ 4-hydroxy-1-tetralone ¡æ central metabolism. In addition, we amplified a diacylglycerol acyltransferase/ wax esther synthase (WS/DGAT) gene from this strain, a key enzyme for TAG biosynthesis; which showed high homology to atf1 from R. opacus PD630 and ro00039 from R. jostii RHA1, two known oleaginous microorganisms. Third, we studied the ability of this strain to produce TAG under diverse culture conditions: NaCl 3% (p/v), pH 10 and 4¨¬ C. In all these conditions strain 602 remained metabolically active, and showed the ability to accumulate TAG. The versatility of Rhodococcus sp. 602 to synthesis TAG from different substrates and under different culture conditions make this microorganism a good candidate for biotechnological production of bacterial oils from wastes of petroleum industry and other organic residues.