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292 Advances in textile biotechnology

composed of a bundle of nanometric size microfibrils (Fig. 12.2). Because
of its characteristic microstructure, bacterial cellulose has a high elastic
modulus (78 GPa), a high tensile strength (at least 2 GPa), and a large
surface area (El-Saied et al., 2004; Guhados et al., 2005). Bacterial cellulose
also has good biocompatibility and an extremely high water content of 90%
or more. Upon removal of water by air drying, the bacterial cellulose will
only rehydrate to the same low extent as that of plant celluloses (about 6%)
after re-exposure to water. After freeze-drying, however, it can absorb up

(a)

2 μm EHT = 10.00 kV Signal A = SE2 Date : 29 Jan 2004
Mag = 5.00 K X WD = 14 mm Photo No. = 7951 Time : 15:16

(b)

2 μm EHT = 10.00 kV Signal A = SE2 Date : 4 Feb 2005
Mag = 5.00 K X WD = 15 mm Photo No. = 7537 Time : 15:56
12.2 SEM images (×5000) of cellulose production from: (a) Aceto-
bacter and (b) wood pulp. Microbial cellulose has a very smooth

network of microfibrils. Wood pulp has similar microfibrils, but they
are part of a larger aggregation of the cell wall remains.

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