Plant cell wall analog

Pallavi Mohekar

Fruit cell wall, a major determinant of fruit textural properties, is composed of biphasic network of cellulose/hemicellulose, embedded in a hydrated matrix of pectin and structural proteins. Its complex nature and very thin size (often < 1 µm) makes the study of the interaction of its components (pectin, hemicellulose and cellulose) and their effect on bulk material properties difficult. Acetobacter xylinus is a bacterium which produces cellulose when incubated at optimum temperature and pH. In this work, we studied an alternative approach of producing cell wall analogue by adding cell wall polysaccharide (pectin and xyloglucan) into Acetobacter xylinus culture medium. The added polysaccharides interact with Acetobacter xylinus cellulose and produce an analog that are similar to the native cell walls at microscopic and molecular level. The incorporation pattern of added polysaccharide into the bacterial cellulose was studied by varying concentration of added polysaccharide (1%, 3%, 5%) in the culture media and incubation period. Increasing xyloglucan concentration increased its incorporation whereas a similar trend of pectin was only observed for 12 day batches. Polysaccharide incorporation was observed to increase with incubation time for 3% and 5% concentrations. 1% level showed insufficiency in polysaccharide after 8th day and hence showed decrease in their incorporation thereafter. The 3%, 12 day batch composition was in closest agreement with in situ apple cell wall composition. It also showed SEM image and FTIR spectrum similar to that of fruit cell wall. We compared these analogs with the fruit cell wall at its various growth and ripening stages. SEM images and FTIR spectra of all the analogs were in agreement with their respective chemical composition. Cell wall analogs are simple in structure, pure in composition and can be used to study combinations of each cell wall component with cellulose. Since analogs with different polysaccharide composition can be produced, they can be used to model mechanical properties as the fruit grows and ripens. Due to relative ease in producing and testing of these analogs, other researchers will be able to use them in their research instead of in situ cell wall.

Plant cell wall analog

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