Research review paper
Xanthan gum: production, recovery, and properties
F. Garcõa-Ochoaa,*, V.E. Santosa, J.A. Casasb, E. Gomeza
Departamento Ingenierõa Quõmica, Facultad de Ciencias Quõmicas, Universidad Complutense de Madrid,
E-28040 Madrid, Spain
Departamento de Quõmica ± Fõsica Aplicada, Facultad de Ciencias,Universidad Autonoma de Madrid,
E-28049 Madrid, Spain
Xanthan gum is a microbial polysaccharide of great commercial significance. This review focuses
on various aspects of xanthan production, including the producing organism Xanthomonas campestris,
the kinetics of growth and production, the downstream recovery of the polysaccharide, and the
solution properties of xanthan. D 2000Elsevier Science Inc. All rights reserved.
Keywords: Biopolymers; Xanthomonas; Xanthomonas campestris; Xanthan gum
Xanthan gum is a natural polysaccharide and an important industrial biopolymer. It was
discovered in the 1950s at the Northern Regional Research Laboratories (NRRL) of the
United States Department of Agriculture (Margaritis and Zajic, 1978). The polysaccharideB1459, or xanthan gum, produced by the bacterium Xanthomonas campestris NRRL B-1459
was extensively studied because of its properties that would allow it to supplement other
known natural and synthetic water-soluble gums. Extensive research was carried out in
several industrial laboratories during the 1960s, culminating in semicommercial production as
Kelzan1 by Kelco1. Substantial commercialproduction began in early 1964. Today, the
major producers of xanthan are Merck and Pfizer the United States, Rhone Poulenc and
Sanofi-Elf in France, and Jungbunzlauer in Austria.
Xanthan gum is a heteropolysaccharide with a primary structure consisting of repeated
pentasaccharide units formed by two glucose units, two mannose units, and one glucuronic
* Corresponding author. Tel.:+34-91-394-4176; fax: +34-91-394-4171.
E-mail address: firstname.lastname@example.org (F. Garcõa-Ochoa).
0734-9750/00/$ ± see front matter D 2000 Elsevier Science Inc. All rights reserved.
PII: S 0 7 3 4 - 9 7 5 0 ( 0 0 ) 0 0 0 5 0 - 1
F. Garcõa-Ochoa et al. / Biotechnology Advances 18 (2000) 549±579
Fig. 1. Structure of extracellular polysaccharide of X. campestris.
acid unit, in themolar ratio 2.8:2.0:2.0 (Fig. 1). Its main chain consists of b-D-glucose units
linked at the 1 and 4 positions. The chemical structure of the main chain is identical to that of
cellulose. Trisaccharide side chains contain a D-glucuronic acid unit between two D-mannose
units linked at the O-3 position of every other glucose residue in the main chain.
Approximately one-half of the terminalD-mannose contains a pyruvic acid residue linked
via keto group to the 4 and 6 positions, with an unknown distribution. D-Mannose unit linked
to the main chain contains an acetyl group at position O-6. The presence of acetic and pyruvic
acids produces an anionic polysaccharide type (Sandford and Baird, 1983). Table 1 shows the
average composition of the various polysaccharides produced by somebacteria of the genus
Xanthomonas (Kennedy and Bradshaw, 1984).
The trisaccharide branches appear to be closely aligned with the polymer backbone. The
resulting stiff chain may exist as a single, double, or triple helix (Morris, 1977; Milas and
Rinaudo, 1979), which interacts with other polymer molecules to form a complex. The
molecular weight distribution ranges from 2 Â 106 to 20 Â 106 Da.This molecular weight
distribution depends on the association between chains, forming aggregates of several
individual chains. The variations of the fermentation conditions used in production are
factors that can influence the molecular weight of xanthan.
Average percent composition of polysaccharides produced by Xanthomonas bacteria (adapted from Kennedy and