Morphological and Metabolic Engineering of to Increase β-Carotene Production.

The oleaginous yeast represents an environmentally friendly platform cell factory for β-carotene production. However, is a dimorphic species that can undergo a yeast-to-mycelium transition when exposed to stress. The mycelial form is unfavorable for industrial fermentation. In this study, β-carotene-producing strains were constructed via the integration of multiple copies of 13 genes related to the β-carotene biosynthesis pathway. The β-carotene content increased by 11.7-fold compared with the start strain T1. As the β-carotene content increased, the oval-shaped yeast form was gradually replaced by hyphae, implying that the accumulation of β-carotene in induces a morphological transition. To relieve this metabolic stress, the strains were morphologically engineered by deleting and genes to convert the mycelium back to the yeast form, which further increased the β-carotene production by 139%. In fed-batch fermentation, the engineered strain produced 7.6 g/L and 159 mg/g DCW β-carotene, which is the highest titer and content reported to date. The morphological engineering strategy developed here may be useful for enhancing chemical synthesis in dimorphic yeasts.