Preparation of Fatty Acid Methyl Esters (FAMEs) from Bacterial Biomass

Bacteria regulate membrane fluidity using membrane lipids, such as fatty acids.

To analyze the fatty acid composition, spread a bacterial inoculum onto a nutrient-rich agar plate and incubate until a lawn forms.

Scrape the lawn, transfer the biomass into a tube, and seal it.

Next, add an alkaline methanolic solution, vortex to disperse the cells, and incubate.

The alkaline solution breaks down membrane lipids, releasing fatty acids and converting them into non-polar fatty acid methyl esters, or FAMEs.

Add acetic acid to neutralize the pH, which stabilizes the FAMEs.

Introduce a non-polar organic solvent and vortex.

The solvent dissolves the FAMEs, which collect in the upper phase, separating them from the aqueous layer and cellular debris.

Transfer the upper phase into a clean tube.

Apply a nitrogen stream to evaporate the solvent. This concentrates the FAMEs while preventing oxidation.

The FAMEs are ready for analysis.

To begin this procedure, prepare a lawn of the bacteria by spreading 100 microliters of an overnight culture of the strain, incubated at 30 degrees Celsius in LB, over the surface of the plate of LB agar medium. Incubate the plate overnight at 30 degrees Celsius.

In order to obtain lipid fatty acids, harvest bacterial cells by scraping colonies from the agar plate and transferring approximately 40 milligrams into a ten milliliter glass tube with a screw cap and PTFE seal. To perform transesterification, add five milliliters of 0.2 molar potassium hydroxide in methanol to the fresh bacterial cells. Vortex, and incubate at 37 degrees Celsius for one hour.

Following this, add one milliliter of one molar acetic acid to lower the pH to seven. Now, add three milliliters of hexane and vortex one minute to extract the fatty acid methyl esters or FAMEs. Transfer the upper phase into clean tubes and concentrate by evaporation at room temperature under a continuous flow of nitrogen to obtain approximately 200 microliters of FAME extract.