The effect of hemicelluloses on biosynthesis, structure and mechanical performance of bacterial...

The primary plant cell wall (PCW) is a specialized structure composed predominantly of cellulose, hemicelluloses and pectin. While the role of cellulose and hemicelluloses in the formation of the PCW scaffold is undeniable, the mechanisms of how hemicelluloses determine the mechanical properties of PCW remain debatable. Thus, we produced bacterial cellulose-hemicellulose hydrogels as PCW analogues, incorporated with hemicelluloses. Next, we treated samples with hemicellulose degrading enzymes, and explored its structural and mechanical properties. As suggested, difference of hemicelluloses in structure and chemical composition resulted in a variety of the properties studied. By analyzing all the direct and indirect evidences we have found that glucomannan, xyloglucan and arabinoxylan increased the width of cellulose fibers both by hemicellulose surface deposition and fiber entrapment. Arabinoxylan increased stresses and moduli of the hydrogel by its reinforcing effect, while for xylan, increase in mechanical properties was determined by establishment of stiff cellulose-cellulose junctions. In contrast, increasing content of xyloglucan decreased stresses and moduli of hydrogel by its weak interactions with cellulose, while glucomannan altered cellulose network formation via surface deposition, decreasing its strength. The current results provide evidence for structure-dependent mechanisms of cellulose-hemicellulose interactions, suggesting the specific structural role of the latter.