Overexpression of the KAS Ⅲ-like gene YxwZ3 increases carotenoids production in Aurantiochytrium sp. SZU445

Abstract

Identifying gene that enhances specific product accumulation of industrial strains is a central tenet of metabolic engineering. Aurantiochytrium sp. has come into the limelight by virtue of their biotechnological importance in the production of bioactive compounds, including fatty acids and carotenoids. However, there is restrict in the high yield of carotenoids in Aurantiochytrium sp. This study, a KAS Ⅲ-like enzyme ‘YxwZ3′ were successfully used to construct recombinant cassette. We utilized TEF1 and EM7 promoters to overexpress KAS Ⅲ-like enzyme YxwZ3 in Aurantiochytrium sp. SZU445. The transformed strain displayed a 4.88-fold increase in the yield of total carotenoids compared to the wild-type strain, involved in β-carotene (37.96 μg/g), phytoene (1.55 μg/g), β-cryptoxanthin (1.57 μg/g), antheraxanthin (0.02 μg/g), α-cryptoxanthin (0.25 μg/g) and echinenone (0.72 μg/g) with the accumulation of fatty acids downregulated. It is speculated that more malonyl-CoA was used in the MVA pathway for carotenoids synthesis based on overexpression of YxwZ3 strains instead of the fatty acid synthesis pathway. In addition, the content of total carotenoids of YxwZ3 overexpression lines was increased 1.33 times (56.52 μg/g) through optimization of fermentation condition based on response surface methodology. These findings demonstrated a significant impact of KAS Ⅲ-like enzyme YxwZ3 on carotenoids in Aurantiochytrium sp., and provided the theoretical basis for constructing the high-yielding carotenoid-producing strains.