RAPID SCREENING OF LIPID PRODUCTION BY COLD ENVIRONMENT BACTERIA

Psychrophile microorganisms, which grow at low temperatures, have great potential in the production of lipids. In the last decade, important alterations have been detected in cellular structures of these microorganisms, such as the increase of unsaturated bonds in the fatty acids of the membrane, which allow its continuous fluidity even at low temperatures. The compounds produced by these microorganisms have great potential in the production of renewable and sustainable biofuels, which has been highlighted by the reduction of environmental impacts. The aim of the present study was to evaluate the production of lipids by bacteria isolated from Antarctic marine samples including marine sponges and sediments. Fifteen bacteria were screened by fluorescence microscopy, through the use of Nile Red dye (9-diethylamino-5H-benzo [α] phenoxaphenoxazine-5-one), a fluorescent and liposelective dye that associates with the neutral lipid molecules of cellular structures, such as the membrane and cell wall. The dye can be excited in the wavelength range from λ = 450 to 560 nm and its fluorescence radiation is measured in the wavelength range λ= 500 to 750 nm. Bacteria cells, previously grown on Petri dishes containing PDA (potato-dextrose agar) culture medium for 7 days at 28 ºC were harvest and transferred to a tube containing distilled water. Cells were centrifuged three times for 10 minutes (10,000 rpm). The dye was dissolved with dimethyl sulfoxide (DMSO), increasing the polarity of the solvent and thus facilitating the entry of the dye into the cell, allowing an increase in fluorescence intensity when compared to the traditional method. The cells were then added to the dye-containing mixture and passed on a slide for viewing through the fluorescence microscope. From the 15 bacteria screened, one isolate showed a yellowish tone in some cells at the 100x magnification, leading to the conclusion that the dye interacted with membrane lipids. The present study shows that the fluorescence methodology can be used as a fast and efficient method to identify microorganisms with potential for the production of lipid compounds, which can be used in the synthesis of hydrocarbons as renewable sources of fuel.