Effect of ethanol on astaxanthin and fatty acid production in the red yeast Xanthophyllomyces dendrorhous

Energy metabolism analysis of exogenous glutamate on promoting co-accumulation of astaxanthin yield and biomass in Phaffia rhodozyma D3

Effective metabolic regulators play an essential role in regulating astaxanthin biosynthesis in Phaffia rhodozyma. In this study, it was found that 5 mM glutamate increased the astaxanthin yield and biomass of P. rhodozyma D3 to 22.34 mg/L and 6.12 g/L, which were 1.22 and 1.33 times higher than the control group, respectively. Meanwhile, glucose uptake was increased and the level of reactive oxygen species (ROS) was reduced with 5 mM glutamate. To further explore the interrelationship between glutamate and astaxanthin synthesis, the energy metabolism of P. rhodozyma D3 with and without glutamate was analysed. Glutamate promoted the Embden-Meyerhof-Parnas pathway (EMP) metabolic flux, modulated the tricarboxylic acid (TCA) cycle and the pentose phosphate pathway (PPP), activated the ornithine cycle and purine metabolism, and provided more ATP and NADPH for astaxanthin accumulation. This study clarified the possible mechanism by which glutamate promoted astaxanthin accumulation in P. rhodozyma.

Sustainable production of astaxanthin in microorganisms: the past, present, and future

Astaxanthin (3,3'-dihydroxy-4,4'-diketo-β-carotene) is a type of C40 carotenoid with remarkable antioxidant characteristics, showing significant application prospects in many fields. Traditionally, the astaxanthin is mainly obtained from chemical synthesis and natural acquisition, with both approaches having many limitations and not capable of meeting the growing market demand. In order to cope with these challenges, novel techniques, e.g., the innovative cell engineering strategies, have been developed to increase the astaxanthin production. In this review, we first elaborated the biosynthetic pathway of astaxanthin, with the key enzymes and their functions discussed in the metabolic process. Then, we summarized the conventional, non-genetic strategies to promote the production of astaxanthin, including the methods of exogenous additives, mutagenesis, and adaptive evolution. Lastly, we reviewed comprehensively the latest studies on the synthesis of astaxanthin in various recombinant microorganisms based on the concept of microbial cell factory. Furthermore, we have proposed several novel technologies for improving the astaxanthin accumulation in several model species of microorganisms.