FACULTY OF INDUSTRIAL SCIENCES AND TECHNOLOGY
UNIVERSITI MALAYSIA PAHANG
TABLE OF CONTENTS
List of Figures
List of Tables
1.2 The Occurance
1.3 Physical Properties
1.5 Industrial Production
1.6 Market Demand
2 PROCESS SELECTION & DESCRIPTION
2.1 Process Selection
2.2 Raw Material
2.3 Process Description
3 STOICHIOMETRIC EQUATION
3.2 Cell Growth
3.3 Substrate Consumption
3.4 Stoichiometric Equation
4 MASS BALANCE
5 METABOLIC PATHWAY & RECOMBINANT TECHNIQUE
5.1 Metabolic Pathways
Xanthan gum is a microbial polysaccharide of great commercial significance. This project
focuses on aspects of xanthan gum production, including the producing organism Xanthomonas
campestris, the production and the product selection, the metabolic pathway, the downstream
recovery and the solution properties of xanthan gum.The objective of this project is to identify
how xanthan gum is produced from Xanthomonas campestris and to learn how organism are
used in fermentation processes and how they are involved in producing fermented product.
Xanthan gum is a polysaccharide, derived from the bacterial coat of Xanthomonas
campestris, used as a food additive and rheology modifier, commonly used as a food thickening
agent (in salad dressings) and a stabilizer (in cosmetic products, to prevent ingredients from
separating). It is produced by fermentation of glucose, sucrose, or lactose by the Xanthomonas
campestris bacterium. After a fermentation period, the polysaccharide is precipitated from a
growth medium with isopropyl alcohol, dried, and ground into a fine powder. Later, it is added to
a liquid medium to form the gum.
It was discovered by an extensive research effort by Allene Rosalind Jeanes and her research
team at the United States Department of Agriculture, which involved the screening of a large
number of biopolymers for their potential uses. It was brought into commercial production by the
Kelco Company under the trade name Kelzan in the early 1960s. It was approved for use in
foods after extensive animal testing for toxicity in 1968. It is accepted as a safe food additive in
the USA, Canada, Europe, and many other countries, with E number E415.
Figures show Xanthomonas campestris (black spots found on a leaf) and it’s isolate.
The repeating unit of xanthan gum.
1.2 THE OCCURANCE
The polysaccharide occurs by inoculating a sterile aqueous solution of carbohydrate(s) a
source of nitrogen, dipotassium phosphate and some trace elements. The medium is well-aerated
and stirred, and the polymer is produced extracellular-ly into the medium. The final
concentration of xanthan produced will vary greatly depending on the method of production,
strain of bacteria, and random variation. After fermentation that can vary in time from one to
four days, the polymer is precipitated from the medium by the addition of isopropyl alcohol and
dried and milled to give a powder that is readily soluble in water or brine. Products of the gum
gene cluster drive synthesis, polymerization, and export of the repeat unit. The easiest way for
the occurrence of xanthan gum will be when Xanthomonas campestris combines with corn sugar,
the result shows a colourless slime called xanthan gum.
1.3 PHYSICAL PROPERTIES
One of the most remarkable properties of xanthan gum is its ability to produce a large
increase in the viscosity of a liquid by adding a very small quantity of gum, on the order of one
percent. In most foods, it is used at not more than 0.5% and can be used in lower concentrations.
The viscosity of xanthan gum solutions decreases with higher shear rates where this is called
pseudo plasticity. This means that a product subjected to shear, whether from mixing, shaking or
even chewing, will thin out but once the shear forces are removed, the food will thicken back up.
It has some skin hydrating properties. Xanthan gum is a gluten free emulsifying agent where it is
easily affected by the changes in temperature. Xanthan gum is beige or off-white powder that
bares a resemblance to sugar but is not as shiny. Xanthan gum is non-toxic and does not inhibit
growth. It is non-sensitizing and does not cause skin or eye irritation. On this basis, xanthan gum
has been approved by the United States Food and Drug Administration (FDA) for use a food
additive without any specific quantity limitations.
A practical use would be in salad dressing, the xanthan gum makes it thick enough at rest
in the bottle to keep the mixture fairly homogeneous, but the shear forces generated by
shaking and pouring thins it, so it can be easily poured. When it exits the bottle, the shear
forces are removed and it thickens back up, so it clings to the salad. Unlike other gums, it is
very stable under a wide range of temperatures and pH.
In foods, xanthan gum is most often found in salad dressings and sauces. It helps to
prevent oil separation by stabilizing the emulsion, although it is not an emulsifier. Xanthan
gum also helps suspend solid particles, such as spices. Also used in frozen foods and
beverages, xanthan gum helps create the pleasant texture in many ice creams, along with guar
gum and locust bean gum. Toothpaste often contains xanthan gum, where it serves as a
binder to keep the product uniform. Xanthan gum when sometimes not made from wheat is
also used in gluten-free baking. Since the gluten found in wheat must be omitted, xanthan
gum is used to give the dough or batter a "stickiness" that would otherwise be achieved with
the gluten. Xanthan gum also helps thicken commercial egg substitutes made from egg
whites, to replace the fat and emulsifiers found in yolks. It is also a preferred method of
thickening liquids for those with swallowing disorders, since it does not change the color or
flavor of foods or beverages.
In the oil industry, xanthan gum is used in large quantities, usually to thicken drilling
mud. These fluids serve to carry the solids cut by the drilling bit back to the surface. Xanthan
gum provides great "low end" rheology. When the circulation stops, the solids still remain
suspended in the drilling fluid. The widespread use of horizontal drilling and the demand for
good control of drilled solids has led to the expanded use of xanthan gum. Xanthan gum has
also been added to concrete poured underwater, to increase its viscosity and prevent washout.
In cosmetics, xanthan gum is used to prepare water gels, usually in conjunction
with bentonite clays. It is also used in oil-in-water emulsions to help stabilize the oil droplets
against coalescence. Xanthan gum is a common ingredient in fake blood recipes, and
in gunges or slime.
It is used in textile printing pastes, ceramic glazes, slurry explosive formulations, and rust
1.5 INDUSTRIAL PRODUCTION
The bacterium Xanthomonas campestris produces the polysaccharide at the cell wall surface
during its normal life cycle by a complex enzymatic process.In nature the bacteria are found on
the leaves of the Brassica vegetables such as cabbage. Commercially, xanthan gum is produced
from a pure culture of the bacterium by an aerobic, submerged fermentation process. The
bacteria are cultured in a well-aerated medium containing glucose, a nitrogen source and various
trace elements. To provide seed for the final fermentation stage, the process of inoculum build-
up is carried out in several stages. When the final fermentation has finished the broth is
pasteurised to kill the bacteria and the xanthan gum is recovered by precipitation with isopropyl
alcohol. Finally, the product is dried, milled and packaged.
Generally, the selected microbial strain is preserved for possible long-term storage by proven
methods to maintain the desired properties. A small amount of the preserved culture is expanded
by growth on solid surfaces or in liquid media to obtain the inoculums for large bioreactors. The
growth of the microorganism and xanthan production are influenced by factors such as the type
of bioreactor used, the mode of operation (batch or continuous), the medium composition, and
the culture conditions (temperature, pH, dissolved oxygen concentration).
Present knowledge of the structure and conformation of xanthan gum explains many of
its unique solution properties. Xanthan gum solutions are highly pseudoplastic. When shear
stress is increased, viscosity is progressively reduced. Upon the removal of shear, the initial
viscosity is recovered almost instantaneously. This behaviour results from the ability of xanthan
molecules, in solution, to form aggregates through hydrogen bonding and polymer entanglement.
This highly ordered network of entangled, stiff molecules results in high viscosity at low shear
rates, and in practical terms, accounts for the outstanding suspending properties of xanthan gum
These aggregates are progressively disrupted under the influence of applied shear, hence
the highly pseudoplastic flow characteristics of xanthan gum solutions. Solutions of xanthan gum
at 1% or higher concentration appear almost gel-like at rest yet these same solutions pour readily
and have low resistance to mixing and pumping. These same qualities are observed at typical use
levels of about 0.1–0.3%. The high viscosity of xanthan gum solutions at low shear rates
accounts for their ability to provide long-term stability to colloidal systems. The reduction in
viscosity in response to increasing shear is important to the pouring properties of suspensions
and emulsions and to the efficacy of xanthan gum as a processing aid.
Effect of pH on viscosity of Xanthan gum
Generally, pH has little effect on the viscosity of xanthan gum solutions over the range
found in food systems. Uniform and high viscosity is maintained over the pH 2 to pH 12, with
some reduction at extreme pH values. However, differences in viscosity are more evident at low
concentrations of xanthan gum. The xanthan gum has excellent stability at low pH over a long
Effect of temperature on viscosity of Xanthan gum
Xanthan gum solutions are unique in their ability to retain their viscosity until a definite
‘melting temperature’ is reached. At this temperature, the viscosity drops sharply due to a
reversible molecular conformational change. The melting temperature is dependent on the
ionic strength of the solution. Above approximately 5% of sodium chloride solution, the melting
temperature is greater than 100ºC. The viscosity loss is reversible characteristic and upon cooling
the original high viscosity is recovered.
Picture shows the production of xanthan gum in industry.
Figure shows an example of packed xanthan gum to be use as food thickener and emulsifier
in baking and culinary industry.
(L strain) Campestris
MEDIUM AND (BATCH SYSTEM)
Alcohol or agent
Alcohol or agent
Alcohol or agent
(WASHING, DEWATERING and DRYING)
Flowchart above shows the outline of the production of xanthan gum in industrial scale.
1.6 MARKET DEMAND
The most growing country for the production of Xanthan gum is China. Xanthan demands a
great economy via China to the world. China has twenty four years history in the production of
xanthan gum, and has witnessed fast development in the past few years, playing an increasing
important role in global xanthan gum supply. And China has become one of the largest xanthan
gum production bases in the world since 2005. For China xanthan gum manufacturers, export
plays an important role, accounting for 70% of total output. Currently, increasing demand for
xanthan gum in domestic market attracts more big scale producers. The demand for xanthan gum
in domestic market has kept 10% growth rate in recently five years.
Raw materials of xanthan gum are mainly corn starch and soybean in China. Corn starch is
the most widely used sugar for xanthan gum production while soybean is used as nitrogen
source. In another hand, coal is also importantly utilised material to produce electricity and steam
for xanthan gum production.
However, because of the intense competition in xanthan gum industry especially in China
itself, this industry has gained lower profit due to the declining xanthan gum price and the cost
for producing xanthan gum is increasing year by year particularly in the past two years. Xanthan
gum is mainly exported to Asia, North of America and Europe countries. Therefore, it is
expected xanthan gum industry have a bright future in the market with the improving people’s
living standard and also change in the dietary structure as well. Thus, xanthan gum industry
prevails in food and pharmaceutical industries in China and also around the world.
The table above illustrates the continuous growth xanthan gum industry in one of the
production company (Fufeng Group) in China from the year 2005 to 2010.