BACKGROUNDThe aim of this study was to evaluate the viscosifying power and mean molecular weight (MMW) of alginate synthesized by Azotobacter vinelandii in a region of very low power input; as well as to scale-up the process of alginate production in a 3 L fermenter using the power input profile (determined in shake flasks) as criterion. RESULTSIn cultures developed at very low power input (P/V) (0.02 to 0.68 kW m(-3)) and maximal oxygen transfer rate (OTRmax) from to 0.85 to 2.8 mmol L-1 h(-1), both the specific growth rate and alginate production were negatively affected. In contrast, the viscosifying power of the alginate increased significantly, with respect to that obtained at the highest power input (1.6 kW m(-3)). This behavior was related to the synthesis of alginates with a high MMW (2240 kDa). When profiles of power input determined in shake flasks at very low P/V were reproduced in a stirred fermentor, it was possible to reproduce the same trends in both the alginate production and the polymer viscosifying power. CONCLUSIONThis study provides useful information in order to implement new scale-up strategies for alginate production, exhibiting chemical characteristics and viscosifying properties superior to commercial alginates. (c) 2015 Society of Chemical Industry