Paper reinforcing by in situ growth of bacterial cellulose

Abstract

The ability of the bacteria Gluconacetobacter sucrofermentans to produce high-quality cellulose is well known. This bacterial cellulose has unique properties, as the result of an ultrathin crosslinked structure. It is almost chemically pure (until 98% cellulose), has a high crystallinity, mechanical strength, elasticity and durability. It is compatible with plant cellulose and could be grown on a vegetal fibrous network what makes bacterial cellulose an excellent candidate to reinforce damaged papers. The objective of this work is to promote the production of bacterial cellulose on the surface of a variety of papers by the direct application of a culture of G. sucrofermentans and to test if this procedure could be an economic and feasible possibility in reinforcing papers or cellulosic surfaces. After 7 days of cultivation, G. sucrofermentans deposits a thin layer (ca. 10 µm) of bacterial cellulose on the papers surfaces. Microscopic observations have shown a heterogeneous covering of the surfaces, while the modified papers maintain their thickness and their basic weight. The treatment has not increased the papers mechanical properties, but maintains them after artificial aging. The changes in optical properties of the reinforced papers, such as opacity and colorimetric coordinates, are minor even after further aging. Air permeance is the paper characteristic that experiences more variations because the layers of bacterial cellulose inhibit the airflow through the papers. The changes in the static and dynamic contact angles suggest that the bacterial cellulose structure is more compact and make the surface more hydrophobic than the original paper surface.