Isolation and partial characterization of cellulose produced by Acetobacter xylinum

A mechanical separation method and an alkali treatment for the isolation of bacterial cellulose were developed. Response surface methodology was employed to determine the optimum conditions for the isolation of bacterial cellulose. A homogenizing mill was used to shear and separate the cellulose fiber from the bacterial cells. Cells were then removed by centrifugation and washing with distilled water. The optimum conditions obtained for the mechanical separation method were 1:1.9 gel to water ratio, 15 min of homogenization and 5 centrifugation-washing cycles. The isolated cellulose had 0.46% nitrogen and 1.46% ash (dry weight basis). The whiteness index (WI) of the product was 30.3 as measured by a Hunterlab colorimeter. For the alkali extraction method, the optimum conditions for the isolation of bacterial cellulose were 0.30 mol/dm(3) NaOH (similar to 1.2%) at 90 degrees C for 25 min. The product had 0.08% nitrogen, 0.66% ash and a WI of 44.2. The isolated bacterial cellulose had 3-5 times higher water holding capacity than commercial cellulose powders as determined by the centrifugation method. Any form of drying reduced its water holding capacity, but it was higher than that of commercial celluloses.