Beta carotene is a tetraterpenoid found in plants, algae, fungi, and bacteria. As a natural precursor for vitamin A and antioxidant, it has various positive effects on the human body. Because of this, it is widely used in the pharmaceutical, food, and cosmetic industries. Since current methods for industrial beta carotene production have proven to be inefficient and unsuitable for human consumption, microbiological biosynthesis gained interest as an alternative method for beta carotene production.
The increasing development in the field of metabolic engineering and synthetic biology made it possible to synthesize beta carotene in a variety of microorganisms, including Escherichia coli. Recent studies show that significant amounts of beta carotene can be obtained in E. coli, but so far are unable to meet industrial needs. Therefore, further optimization of beta carotene biosynthesis in bacterial cells is required. This can be achieved by optimization of gene expression in different biosynthetic pathways, involved in beta carotene biosynthesis. To perform this time-consuming and repetitive work that requires high accuracy, our group developed an automated high-throughput screening platform using a liquid-handling robot to optimize gene expression in the beta carotene biosynthetic pathway. Our method is based on a combinatorial construction of plasmids with different gene regulatory elements. Using this method, we prepared and characterized 22 different strains with altered expression of genes for beta carotene biosynthesis.
By optimizing gene expression and cultivation conditions, we achieved 13.5-fold higher beta carotene yields in bacterial cells. Our automated platform can be used for gene expression optimization on a larger scale, which can lead to faster identification of strains with the highest production of beta carotene. It can also be used as a tool to optimize gene expression in the biosynthesis of other valuable molecules.
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