BACKGROUND More extensive utilization of bacterial nanocellulose (BNC) is severely restricted by the low efficiency and small scale of the traditional static cultivation. Submerged fermentation in stirred-tank reactors (STRs) is potentially favourable for large-scale production of BNC, but scale-up of cultivation remains challenging. Even though the STR is most commonly used for submerged cultivation in the fermentation industry, there are few previous attempts to scale-up production of BNC to pilot scale using an STR. Furthermore, the question of how scale-up of submerged cultivation affects the properties of the BNC has received very little attention RESULTS Four strains were compared in 250-mL shake flasks. Strain DHU-ATCC-1 displayed the highest volumetric productivity, 0.56 g L-1 d(-1), and was then cultivated in a 400-mL STR, showing a similar productivity of 0.55 g L-1 d(-1). Scale-up using a 75-L STR pilot bioreactor resulted in enhancement of the BNC production rate from 0.056 g d(-1) in the shake flasks to 17.3 g d(-1) in the 75-L STR, although the productivity decreased to 0.43 g L-1 d(-1). During scale-up from shake flasks to 400-mL STR and further on to 75-L STR, the BNC fibers formed more bundles, whereas the fiber diameter decreased from 25.6 to 21.7 nm. The BNC from the 75-L STR exhibited a higher degree of polymerization, specifically 3230, higher degree of crystallinity, specifically 83%, larger crystallites, and improved strength including higher tensile energy absorption index and superior stretch at break. CONCLUSION It is possible to enhance BNC production, and maintain or improve its properties when scaling up submerged cultivation in STRs. (c) 2018 Society of Chemical Industry