Ej. Vandamme et al., IMPROVED PRODUCTION OF BACTERIAL CELLULOSE AND ITS APPLICATION POTENTIAL, Polymer degradation and stability, 59(1-3), 1998, pp. 93-99
Bacterial cellulose, produced by Acetobacter species, displays unique
properties, including high mechanical strength, high water absorption
capacity, high crystallinity, and an ultra-fine and highly pure fibre
network structure. It is expected to be a new commodity biochemical wi
th diverse applications, if its mass production process could be impro
ved, especially via submerged fermentation technology. It has already
found application as a food matrix (nata de coco) and as dietary fibre
, as a temporary dressing to heal skin burns, as an acoustic or filter
membrane, as ultra-strength paper and as a reticulated fine fibre net
work with coating, binding, thickening and suspending characteristics.
A wet spinning process for producing textile fibres from bacterial ce
llulose has also been developed, and applications as a superconducting
and optical fibre matrix are under study. We have been able to improv
e bacterial cellulose production in surface culture (up to 28 g/l), as
well as in submerged culture (up to 9 g/l) via strain selection, muta
tion, medium composition optimization and physico-chemical fermentatio
n parameter control. Glucose and fructose as the carbon source and ace
tic acid as the energy source, combined with a precise control of pH a
nd dissolved oxygen levels, results in highly improved cellulose yield
s. An internal pH control in stationary surface cultures was achieved
by an appropriate choice of the ratio of fructose/glucose/acetic acid.
It was also demonstrated that cellulose formation could be enhanced b
y adding insoluble microparticles such as diatomaceous earth, silica,
small glass beads and loam particles to submerged, agitated/aerated Ac
etobacter cultures. This microcarrier-enhanced cellulose synthesis cou
ld be the result of the formation of microenvironments with locally lo
wered dissolved oxygen levels because of the attachment of Acetobacter
cells as a biofilm on the particles. As such, less glucose is lost as
gluconate, saving it for cellulose formation and maintaining the pH p
rofile within the desirable range. We have also developed a UV-mutatio
n and proton enrichment strategy, which allows the selection of A. xyl
inum mutants, which are highly restricted in (keto)gluconate synthesis
and produce cellulose more efficiently, even under oxidative culture
conditions. Combining these nutritional, genetic and bioprocess-techno
logical improvements, very high levels of bacterial cellulose have bee
n attained. Further improvements are needed to arrive at an economical
fermentation process for mass production of bacterial cellulose. (C)
1998 Elsevier Science Limited. All rights reserved.