Production of FucoPol by Enterobacter A47 using waste tomato paste by-product as sole carbon source

•Enterobacter A47 was cultivated on tomato paste by-product as sole carbon source.•Tomato paste supported cell growth and was used for exopolysaccharide synthesis.•High volumetric productivity was reached with continuous substrate feeding.•Tomato paste was successfully valorized into FucoPol.

Out-of-specification tomato paste, a by-product from the tomato processing industry, was used as the sole substrate for cultivation of the bacterium Enterobacter A47 and production of FucoPol, a value-added fucose-rich extracellular polysaccharide. Among the different tested fed-batch strategies, pH-stat, DO-stat and continuous substrate feeding, the highest production (8.77 g L−1) and overall volumetric productivity (2.92 g L−1 d−1) were obtained with continuous substrate feeding at a constant flow rate of 11 g h−1. The polymer produced had the typical FucoPol composition (37 mol% fucose, 27 mol% galactose, 23 mol% glucose and 12 mol% glucuronic acid, with an acyl groups content of 13 wt%). The average molecular weight was 4.4 × 106 Da and the polydispersity index was 1.2. This study demonstrated that out-of-specification tomato paste is a suitable low-cost substrate for the production of FucoPol, thus providing a route for the valorization of this by-product into a high-value microbial product.