*4.6. Measurement of the Effects of Water Potential on Water Content of Bacterial Cellulose and Cellulose Composites*

Segments of bacterial cellulose or cellulose composite, 2 mm × 1 mm in cross-section and approximately 10 mm in length, were cut from the cellulose and cellulose composites with a pair of razor blades held in a spaced block and transferred to MES buffer for at least 10 min at room temperature. Segments were then blotted quickly using absorbent paper

to remove surface buffer, and their initial weight measured quickly using a microbalance. The pieces were then transferred into Eppendorf tubes containing 800 μL of MES buffer containing PEG 6000 solution (0.27 g PEG 6000 g water−1, giving an osmotic potential of −0.62 MPa, determined using a Vapor® 5520 osmometer as noted above) and the weight changes were measured at regular intervals for 180 min by removing the segments from the buffer, quickly rinsing them in MES buffer without PEG to remove the viscous PEG solutions, blotting them to remove surface liquid, and again weighing them before returning them to the tubes of MES buffer with PEG. After 180 min, the pieces were transferred to Eppendorf tubes containing 800 μL of control MES buffer without PEG to rehydrate, and the weight changes again were recorded at regular intervals. Finally, 11.2 μg of α-expansin or 200 μL of snail powder extract was added to the MES buffer, and any further changes in weight were recorded.
