Modification of azo dyes by lactic acid bacteria

Authors: Perez Diaz, Ilenys; McFeeters, Roger

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2008
Publication Date: 8/1/2009
Citation: Perez Diaz, I.M., McFeeters, R.F. 2009. Modification of azo dyes by lactic acid bacteria. Journal of Applied Microbiology. 107:584-589.

Interpretive Summary: The pickle vegetable industry has sporadically reported cases of red color spoilage, which consist of the appearance of a red deposit on the fruit skins, approximately one week post-packing. The ability of the lactic acid bacteria Lactobacillus casei and Lactobacillus paracasei to utilize the azo dye tartrazine was identified as the primary cause of this type of spoilage, as part of previous work. Here we describe the ability of other lactic acid bacteria to modify tartrazine and other azo dyes. It was revealed that the bacteria isolated from the red colored spoilage are more efficient at modify tartrazine as compare to the other bacteria tested. Results suggest that the product, which may be involved in the red colored spoilage is bigger than its parent molecule, tartrazine.

Technical Abstract: Identification of microorganisms capable of utilizing azo dyes have been an area of significant interest due to their role in the treatment of waste water derived from the textile industry. The ability of L. casei LA1133 and L. paracasei LA0471 to modify the azo dye tartrazine was recently documented as the result of the investigation on red colored spoilage in acidified cucumbers. The ability of fifteen other lactic acid bacteria (LAB) to modify the coloring agent, tartrazine and other azo dyes was studied. Most LAB were capable of modifying tartrazine under anaerobic conditions, but not under aerobic conditions. Lactobacillus delbruckii, Pediococcus pentosaceous, and Lactobacillus brevis were incapable of modifying the dyes under anaerobic and aerobic conditions. Growth rate and yield of the LAB capable of modifying the dyes were not affected by their presence in the culture medium. The product of the tartrazine modification by LAB was identified as a molecule 111 amu larger than its precursor. This product has a purple tint under aerobic conditions and is colorless under anaerobic conditions. It absorbs light at 361 and 553 nm. Although, microorganisms capable of reducing the azo bond on multiple dyes have been known for decades, this is the first report of anabolism of azo dyes by food related microorganisms, such as LAB.