Effect of cellulose crystallinity on bacterial cellulose assembly

Bacterial cellulose (BC) is a promising biomaterial as well as a model system useful for investigating cellulose biosynthesis. BC produced under static cultivation condition is a hydrous pellicle consisting of an interconnected network of fibrils assembled in numerous dense layers. The mechanisms responsible for this layered BC assembly remain unknown. This study used calcofluor as a fluorescent marker to examine BC layer formation at the air/liquid interface. Layers are found to move downward into the media after formation while new layers continue to form at the air/liquid interface. Calcoflour is also known to reduce the crystallinity of cellulose, changing the mechanical properties of the formed BC microfibrils. Consecutive addition and accumulation of calcofluor in the culture medium is found to disrupt the layered assembly of BC. BC crystalllinity decreased by 22 % in the presence of 12 % calcofluor (v/v) in the medium as compared to BC produced without calcofluor. This result suggests that cellulose crystallinity and the mechanical properties which crystallinity provides to cellulose are major factors influencing the layered BC structure formed during biosynthesis.