Toxicity of Organic Acids

Organic acids are used in industry to act as everything from food preservatives to antiseptics and disinfectants. Years of testing and use have shown that certain organic acids successfully kill harmful bacteria without harming consumers or the environment. However, large corporations are concerned about the amounts of varying acids they must add in material production and the effects that long-term subsequent use may cause. This study seeks to find the acid most effective at killing certain strains of bacteria. To determine this, the microorganisms Xylosoxydans, Pseudomonas fluoresens, Staphylococcus aureus, Bacillus pumilus, Serratia marcescens, I.47, and a mutant strain were placed on separate agar plates and paper disks soaked in acetate, citrate, formate, lactate, oxalate, and propionate, respectively, were placed on each plate and stored at 30 degrees centigrade for five to six days. The effectiveness of each acid was determined by the size of the "zone of inhibition" surrounding the disk, or the clear area in which bacterial growth was restricted by the acid. The disk with the largest zone of inhibition for a particular organism is considered the most effective organic acid for that particular organism.