Abstract:

Steroids are widely distributed in natural organisms and play essential roles in growth, breeding, metabolic regulation, and endocrine homeostasis. To date, diverse steroids have been proved to have numerous therapeutic effects on reproductive health, endocrine regulation, inflammation, etc. and can be used as life-saving drugs for some serious diseases, such as cancer, organ transplantation, and serious infection. Therefore, the industrial synthesis of steroid drugs has developed rapidly and steroid drugs have become the second largest drug category just ranked after antibiotics. Due to the complex structure and delicate configuration, steroids are difficult to be produced at an industrial scale by chemical total synthesis. At present, steroids are mainly produced by semi-synthesis ways with natural steroidal sapogenins or sterols as raw materials via the combination of chemical and biological transformations. However, the above routes are long and complex resulting in the low yield and the overuse of toxic reagents and heavy metal catalysts, thus resulting in a large quantity of wastewater and residue as well as high production costs. Therefore, it is necessary to develop green biomanufacturing technologies, such as biocatalysis, biotransformation, and biosynthesis, for the industrial production of steroids. Currently, the production mode of steroids has been profoundly changed due to the successful application of enzyme-catalyzed reactions and microbial transformations in the industrial production of steroids. It is expected that the production of steroids will be changed into a biomanufacturing mode if the robust microbial cell factories for the de novo biosynthesis of steroids can be developed via the biosynthetic way. The de novo synthesis of steroids by microorganisms has been materialized. However, due to the extraordinarily complex metabolic mechanism of steroids in the nature, the efficient production of steroids in engineered hosts still remains a challenge. Here, starting from the evolution of steroidal pharmaceutical industry, we systematically review recent advances in biomanufacturing technologies of steroids, including the identification and application of steroidal biocatalysis and biotransformation, the characterization and modification of the metabolic mechanisms of steroids in certain microorganisms, and the development of de novo biosynthesis pathways of steroids in engineered cell factories. From the above three aspects, this review provides a reasonable summary and prospect for the current status and future development trend of green bio-manufacturing technologies in the steroidal pharmaceutical industry.

Key words: steroids, green biomanufacturing, biocatalysis and biotransformation, de novo biosynthesis, microbial cell factories

摘要：

甾体化合物（简称甾体）分布广泛、功能卓越，在机体生长、物种繁育以及代谢调控等方面，发挥着难以取代的生理功能。因此，天然甾体及其衍生物被广泛用于生殖健康、内分泌调控等领域，是器官移植、重症感染等许多危重疾病的“刚需药”和“救命药”。甾体结构复杂、构型精巧，很难通过化学全合成来生产，当前主要以天然甾体皂素或甾醇为原料，通过化学与生物转化相结合的半合成法获得。然而，甾体药物的生产路线长、工艺复杂、收率低，涉及大量有毒有害试剂和重金属催化剂的使用，污水废渣排放量大、处理难度高，总体成本居高不下。为改变此局面，推动产业的转型升级，大力开发绿色生物制造技术是行业健康发展的大势所趋。当前，甾体制药工业正处于以生物催化转化取代化学合成的产业升级阶段，随着高效酶和细胞转化的成功应用，传统的甾体生产模式正发生着深刻变化。在此基础上，若能进一步利用合成生物学技术，创建可高效从头合成甾体的微生物细胞工厂，则将彻底改变甾体制药的工业模式，切实实现甾体药物的绿色制造。近年来，已有利用微生物从头合成部分甾体化合物的报道，然而由于甾体的天然合成机制异常复杂，如何实现细胞工厂的高效生产，仍是目前面临的主要挑战。本文从甾体药物生产方式的演变出发，系统综述了甾体生物催化转化和从头合成的最新进展，重点阐述了甾体生物催化转化酶的挖掘及改造、微生物代谢转化甾醇机制的解析及转化细胞工厂的开发、微生物从头合成甾体人工路线的创建三部分内容，以期对甾体药物绿色生物制造的现状和趋势做出合理的总结与展望。

关键词: 甾体化合物, 绿色生物制造, 生物催化转化, 从头生物合成, 微生物细胞工厂