Biotransformation of Phytosterols to Androst-1,4-Diene-3,17-Dione by <i>Mycobacterium </i>sp. ZFZ Expressing 3-Ketosteroid-Δ¹-Dehydrogenase

• Main Authors: Xiangcen Liu, Ruijie Zhang, Zhiwei Bao, Chenyang Yuan, Huijin Cao, Jiping Shi, Junsong Sun, Baoguo Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2020-06-01
• Series: Catalysts
• Subjects: KSDD; Androst-1,4-diene-3,17-dione(ADD); phytosterols; waste cooking oil; biotransformation
• Online Access: https://www.mdpi.com/2073-4344/10/6/663

As an important hormone drug intermediate, androst-1,4-diene-3,17-dione can be bio-converted from phytosterols. However, separation and purification in the downstream process are very difficult due to the similarity in structure and physiological characteristics between ADD and androstenedione (AD). This phenomenon was correlated to the insufficient enzyme activity of 3-ketosteroid-Δ¹-dehydrogenase (KSDD), which specifically catalyzes the C_1,2dehydrogenation of AD. In order to obtain a highly purified ADD from phytosterols, the dehydrogenation effect of different kinds of KSDDs and the transcription effect of four promoter sequences on <i>ksdd</i> were analyzed in <i>Mycobacterium </i>sp. ZFZ (ZFZ), the cell host that transform phytosterols to AD in the oil-aqueous system. A tandem KSDD expression cassette containing strain ZFZ-2111 yielded 2.06 ± 0.09 g L^-1 ADD, with a molar ratio of ADD/AD at 41.47:1.00 in 120 h. In waste cooking oil-aqueous media, the proportion of ADD in the fermentation by ZFZ-2111 was 92%. The present study provides a reliable theoretical basis for the step-by-step transformation of phytosterols to ADD.