High-titer production of staurosporine by heterologous expression and process optimization

Enhancement of doxorubicin production in Streptomyces peucetius by genetic engineering and process optimization

Doxorubicin is an important class of anthracycline antitumor antibiotics produced by Streptomyces peucetius. The doxorubicin fermentation yield of the wild-type strain was very low, so it could not be produced directly by fermentation at an industrial scale due to the high cost. In the present study, S. peucetius SIPI-7-14 was obtained from SIPI-14 through several rounds of doxorubicin resistance screening. Then, the ketoreductase gene dnrU was knocked out to reduce (13S)-13-dihydrodaunorubicin production, and the resistance gene drrC was overexpressed to further enhance resistance to doxorubicin. The resulting engineered strain S. peucetius △U1/drrC produced 1128 mg/L doxorubicin, a 102.1% increase compared to that of SIPI-14. Then, fermentation medium was optimized using the response surface method. In the optimized fermentation medium, the yield of doxorubicin was increased to 1406 mg/L in shake flask on the 7th day. Furthermore, batch culture was carried out in a 10 L fermenter, and the concentration of doxorubicin reached 1461 mg/L after 7 days of culture, which was the highest yield reported to date, indicating the potential for industrial production of doxorubicin by fermentation.

Transformation-associated recombination (TAR) cloning and its applications for gene function; genome architecture and evolution; biotechnology and biomedicine

Transformation-associated recombination (TAR) cloning represents a unique tool to selectively and efficiently recover a given chromosomal segment up to several hundred kb in length from complex genomes (such as animals and plants) and simple genomes (such as bacteria and viruses). The technique exploits a high level of homologous recombination in the yeast Sacharomyces cerevisiae. In this review, we summarize multiple applications of the pioneering TAR cloning technique, developed previously for complex genomes, for functional, evolutionary, and structural studies, and extended the modified TAR versions to isolate biosynthetic gene clusters (BGCs) from microbes, which are the major source of pharmacological agents and industrial compounds, and to engineer synthetic viruses with novel properties to design a new generation of vaccines. TAR cloning was adapted as a reliable method for the assembly of synthetic microbe genomes for fundamental research. In this review, we also discuss how the TAR cloning in combination with HAC (human artificial chromosome)- and CRISPR-based technologies may contribute to the future.