Water transport properties of artificial cell walls

The cell wall is an essential structural component of the fruit cell. It is also an important barrier for water exchange between the intercellular space and the cytoplasm and as such affects moisture loss of fruit during commercial storage. In this manuscript the nanostructure and water exchange properties of different artificially produced cell walls were investigated. Three artificial cell walls, bacterial cellulose (BC), bacterial cellulose with pectin (BCP) and bacterial cellulose with pectin and xyloglucan (BCPX), were prepared using a culture of Gluconoacetobacter xylinus in Hestrin and Schramm medium. The microscopic structure of three artificial cell walls was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface images showed clear differences in the diameter of the microfibrils and the density of the fibril network. The degree of compactness was highest for BCPX, than BCP and BC. Desorption isotherms of the three artificial cell walls were measured. It was found that the water retention capacity at the same water activity was higher for BC than for the other two artificial cell walls: BCP had higher water retention capacity than BCPX. Cellulose has a high water retention capacity that increases with increasing void space ratio in cellulose containing membrane. The resulting water conductivity values of the different artificial cell walls at 3 degrees C/95% RH and 25 degrees C/85% RH were measured. The lowest value of water conductivity was found for BCPX while the highest value was found for the pure BC. Adding pectin had a strong effect on the water conductivity, while xyloglucan did not have any appreciable additional effect. The structural properties were related to the water transport properties. (C) 2011 Elsevier Ltd. All rights reserved.