Characterization and improvement of curdlan produced by a high-yield mutant of Agrobacterium sp. ATCC 31749 based on whole-genome analysis.

• The curdlan biosynthesis mechanism can be determined based on whole-genome analysis. • Mutant CGMCC 11546 produced 1.34-fold more curdlan than the WT strain. • The maximum curdlan production was 47.97 ± 0.57 g/L (16 % increase) after optimization. • Deletion of exoK and exsH increased the gel strength and molecular weight of curdlan. • Noodles supplemented with curdlan from Δ exoK-exsH had excellent eating quality. Curdlan is a bacterial, water-insoluble, linear homopolysaccharide that has been widely used in the food industry. In this study, genome information of strain CGMCC 11546, a UV-induced high-yield mutant of the model curdlan-producing strain Agrobacterium sp. ATCC 31749, was used to investigate the molecular mechanism of curdlan biosynthesis. The maximum curdlan yield of 47.97 ± 0.57 g/L was obtained from strain CGMCC 11546 by using optimal media containing 60 g/L sucrose, 6 g/L yeast, 2 g/L KH 2 PO 4 , 0.4 g/L MgSO 4 ·7H 2 O, 2 g/L CaCO 3 , 0.1 g/L FeSO 4 ·7H 2 O, 0.04 g/L MnSO 4 , and 0.02 g/L ZnCl 2 at 30 °C and 280 rpm after 96 h of fermentation. The gel strength of curdlan was improved by 41 % by knocking out the β-1,3-glucanase genes exoK and exsH of strain CGMCC 11546. Furthermore, the application of curdlan from the Δ exoK-exsH strain in noodles significantly improved the eating quality of both raw and cooked noodles. [ABSTRACT FROM AUTHOR]