Now who all is in on this whole gluten-free diet? If so, you better start thanking this guy right here...

Try imagining pouring out your salad dressing from its container and all you get is the oil, followed by the rest of the ingredients, yum right?  Or how about when you consume frozen food and all you get once they are heated up is mush and experience none of the pleasurable feelings of the food, yum right? No, ew!


Well you can give a huge shout out to Xanthomonas campestris, more specifically to its “oozy” outer coating that is composed of primarily a polysaccharide.  Initially this “ooze” is secreted by the bacteria to be used as a protective layer.  This exopolysaccharide slime is used to defend off attack from bacteriophage as well as serve as a barrier from environmental damage during its dormant stages in life, usually during winter months because Xcc doesn’t form any type of endospores or cysts.  The polysaccharide the makes up the "oozy" outer coating is more formally known as xanthan gum, a common food additive.

The use of xanthan gum is very beneficial to the food industry however it is a complex process to extract this heteropolysaccharide from Xcc.  For proper execution of this process a multienzyme system is required.  Initially there is an uptake of carbohydrate substrates through active transport or facilitated diffusion from the outer coating.  The microbial strains that are selected are held in a long-term storage in order to preserve the correct properties needed for further processing.  A small fragment of the culture is then used and grown into an appropriate inoculum for a bioreactor.  While the medium is being mixed and ventilated the polymer produces extracellularly.  It is difficult to give a specific amount of xanthan that will be produced because that mainly relies on the initial bacteria strain and the exact mechanism used to produce the polymer.  After fermentation occurs, varying from one to four days, there is a broth found as the byproduct.  Within this broth are xanthan, bacterial cells, and other components.  Multiple filtrations are done to separate out the main cells.  Isopropanol is then added to form a precipitate of xanthan, which is then dried and packaged for manufacturing.

Xanthan gum’s structure consists of a primary structure consisting of repeated pentasaccharide units formed by two glucose units, two mannose units, and a glucuronic acid unit.  Its main chain consists of beta-D-glucose units with linkages at the 1 and 4 positions, very similar structure to cellulose.  The repeating segments of pentasaccharide units give xanthan gum its backbone, which is a unique characteristic of this heteropolysaccharide.  Below is the overall structure of xanthan.

Image copyright Antonio Zamora

Xanthan gum is a widely used food additive in the food industry.  It is a common replacement for common food additive, gluten.  Whether it is based on being allergic to wheat or just simply taking part in a gluten-free diet, xanthan gum is most likely your predominate substitute.  It has multiple uses, specially used in adding viscosity and suspension, and to stabilize mixtures of liquids within food products.  Xanthan gum is a polysaccharide used not only in the food industry but also in agriculture, cosmetics and pharmaceuticals.  Xanthan gum is identified as a cream colored powder which constantly holds a high viscosity within both hot and cold solutions.  This characteristic gives xanthan gum the ability to aid in many different applications.  Xanthan gum is approved by the United States Food and Drug Administration to be used in human food which allows it to be used in a variety of food and product production.  With the high demand of frozen food and mixtures of liquid there is a need for a food additive that can produce a unique texture expression, viscosity, flavor release, appearance, and control water properties, and that food additive is xanthan gum.  Its most common characteristic would be its ability to keep oily mixtures mixed together when needed, such as within dressings.  It allows settling of higher density ingredients but once mixed xanthan gum holds the ingredients together long enough to pour evenly out of the container, this process is commonly known as a pseudoplastic property in solutions.  See the table below for more examples of how xanthan gum is used in the food industry as well as other manufacturing departments.


After understanding the significance of xanthan gum in the food industry, the importance and significance of Xanthomonas campestris is looked at on a whole new level.  This normally known plant pathogen is actually held at high demand within human food production.  It can be stated that Xcc is sustainable as a food source due to the applications that its byproduct, xanthan gum has with a multitude of different products.


Wow that is one cool organism if you ask me.  On one side it is a devastating plant pathogen but then can be a successful and desirable food additive for the human food production.  I wonder what other cool facts Xanthomonas campestris can have!