Bacterial nanocellulose (BNC) is mainly synthesized by acetic acid bacteria. As plant cellulose, BNC is an unbranched polymer composed of beta-1,4-linked glucopyranose residues. However, BNC has much higher crystallinity and higher degree of polymerization (DP), as well as other attractive physiochemical properties. Due to the high cost of the medium (particularly the carbon source) used for cultivation of bacteria and low productivity, wider use of BNC is severely restricted. Pulp and paper mills normally produce large amounts of cellulose waste including fiber sludge, a residual stream of little or no value. In a biorefinery perspective, it would be desirable to convert waste cellulose to high value-added products. In this work, we investigated the possibility to produce BNC using an enzymatic hydrolysate of waste fiber sludge in a stirred-tank bioreactor. The potential benefits of including BNC in papermaking were also explored. Compared with synthetic glucose-based medium, the productivity of BNC from fiber sludge hydrolysate was significantly enhanced, although the DP was somewhat lower. The cultivation conditions used in stirred-tank bioreactors, including stirring speed, airflow and pH, were further investigated. After optimization, the BNC productivity was almost three times of that using synthetic glucose-based medium in shake flasks. Finally, the BNC produced from the fiber sludge hydrolysate was used as an additive in papermaking based on chemithermomechanical pulp (CTMP) of birch. Inclusion of BNC resulted in significant enhancement of tensile strength and tear resistance. For example, with 10% (w/w) BNC in the CTMP/BNC mixture the tear resistance was enhanced by 140%. Scanning electron microscopy images of the sheets showed that BNC cross-linked the CTMP fibers resulting in enhanced mechanical strength.

Production of bacterial nanocellulose from waste fiber sludge and its use in papermaking

254th National Meeting (2017)

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