From Low-Cost Miscanthus × giganteus to Valuable Bacterial Nanocellulose: A Complete Technological Cycle

The concept of bacterial nanocellulose (BNC) production from low-cost cellulosic raw materials is evolving across the world, as it reduces the production cost of this valuable polymer and expands its technical applications. Miscanthus × giganteus is a widely recognized energy crop with high cellulose content, but its potential as a feedstock for BNC production is underexplored. The cellulose content in the biomass of Miscanthus × giganteus from the Russian breeding stock was 54% in the present study. The Miscanthus × giganteus biomass was subjected to chemical pretreatment by four different techniques: classical alkaline delignification and three authors’ own methods using diluted nitric acid solutions at atmospheric pressure. The resultant substrates were then enzymatically hydrolyzed under identical conditions, yielding carbohydrate-based culture media on which bacterial nanocellulose biosynthesis was carried out using a SCOBY symbiotic culture. All the four chemical pretreatment methods were found to be extremely efficient because they provide a 28–31-fold increase in the biomass reactivity to enzymatic hydrolysis compared to untreated Miscanthus × giganteus. This study clearly demonstrates that it is most expedient to carry out the biomass pretreatment in a single stage using a dilute nitric acid solution in the BNC production technology from Miscanthus × giganteus. In this case, the substrate yield from the feedstock for subsequent hydrolysis was 50%, the recovery of reducing sugars from the Miscanthus × giganteus biomass reached its maximal value (65.2%), and the yield of BNC was 1.1–1.3 times higher compared to the other three methods of biomass pretreatment.