Biotransformation Enables Innovations Toward Green Synthesis of Steroidal Pharmaceuticals.

Steroids have been widely used in birth-control, prevention, and treatment of various diseases, representing the largest sector after antibiotics in the global pharmaceutical market. The steroidal active pharmaceutical ingredients (APIs) have been produced via partial synthetic processes first mainly from sapogenins, which was converted into 16-dehydropregnenolone by the famous "Marker Degradation". Traditional mutation and screening, and process engineering have resulted in the industrial production of 4-androstene-3,17-dione (AD), androst-1,4-diene-3,17-dione (ADD), 9α-hydroxy-androsta-4-ene-3,17-dione (9α-OH-AD), and so on, which serve as the key intermediates for the synthesis of steroidal APIs. Recently, genetic and metabolic engineering have generated highly efficient microbial strains for the production of these precursors, leading to the replacement of sapogenins with phytosterols as the starting materials. Further advances in synthetic biology hold promise in the design and construction of microbial cell factories for the industrial production of steroidal intermediates and/or APIs from simple carbon sources such as glucose. Integration of biotransformation into the synthesis of steroidal APIs can greatly reduce the number of reaction steps, achieve lower waste discharge and higher production efficiency, thus enabling a greener steroidal pharmaceutical industry.