Effect of Drying Methods on Rehydration of Bacterial Cellulose

  Objective  Effects of drying methods on rehydration property of bacterial cellulose (BC) were investigated.

  Method  BC samples dried by means of hot air, microwave under vacuum, and freeze-drying were compared on the swelling and reconstitution rates upon rehydration. A scanning electron microscope (SEM) was used to observe and characterize the BC microstructure.

  Result  The varied dehydration processes affected the microstructure and rehydration of the dried BC. Among the untreated control and treated samples, the freeze-dried BC displayed the highest rehydration rate of 44.79%. It was followed by the hot air and the microwave-vacuum dried specimens. The SEM images showed the freeze-drying rendered BC with a loose but well-defined fibrous network, while the other two methods produced a tight structure with clusters. Insofar as hygroscopic property is concerned, freeze-drying BC at −80 ℃ was superior to all other methods. The dynamics of the water adsorption and swelling of BC followed the Fickian diffusion law. A better maintained 3D structure would have greater diffusion coefficient, and therefore, more efficient water absorption for the dried BC when water was added.

  Conclusion   The freeze-dried BC could be rehydrated most desirably among all tested samples. The processing technology was recommended for the dehydration.