Improved production of carotenoid-free welan gum in a genetic-engineered Alcaligenes sp. ATCC31555

Objective To improve the production of welan gum and obtain a carotenoid-free strain while reducing the fermentation and post-treatment costs. Results The vitreoscilla globin ( vgb ) gene combined with the β-galactosidase (lacZ) promoter was inserted into the phytoene synthase ( crtB ) gene region of the chromosome in Alcaligenes sp. ATCC31555. When the recombinant strain was grown in a 5 l fermentor, welan gum was produced at 24 ± 0.4 g l −1 compared to 21 g ± 0.4 g l −1 in the wild type. Furthermore, the carotenoid-free welan gum produced using Alcaligenes sp. ATCC31555 VHb strain was less expensive with improved properties. Conclusions Alcaligenes sp. ATCC31555 VHb strain was a better neutral welan-producing strain with a higher production than the wild-type strain.