Lycopene over-accumulation by disruption of the negative regulator gene crgA in Mucor circinelloides

Lycopene has become one of the most interesting antioxidant compounds, especially in relation to human health. This work describes a genetic strategy to modify the carotenoid biosynthesis pathway to develop a lycopene-overproducing strain. The crgA gene, a negative regulator of carotenogenesis, was disrupted in the Mucor circinelloides strain MU202, which lacks the lycopene cyclase activity and accumulates lycopene instead of beta-carotene. The resultant strain, MU224, demonstrated increased transcriptional levels of the carotenogenesis structural genes carRP and carB compared to the parental strain MU202. As a consequence, strain MU224 accumulated 5 mg/g of dry weight of cells in liquid cultures, a sevenfold increase with respect to the parental strain. Moreover, when lycopene production was examined in a complex enriched medium, biomass increased tenfold compared to that obtained in synthetic minimal medium. In this complex medium, the production rate of lycopene by strain MU224 reached 54 g/l. These results illustrate how a combination of genetic manipulation and optimized culture conditions can be utilized to enhance the production of commercially desirable compounds such as lycopene.