Novel osmotic stress control strategy for improved pneumocandin B0 production in Glarea lozoyensis combined with a mechanistic analysis at the transcriptome level
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Pneumocandin B0, the precursor of the antifungal drug caspofungin, is a secondary metabolite of the fungus Glarea lozoyensis. In this study, we investigated the effects of mannitol as the sole carbon source on pneumocandin B0 production by G. lozoyensis. The osmotic pressure is more important in enhancing pneumocandin B0 production than is the substrate concentration. Based on the kinetic analysis, an osmotic stress control fed-batch strategy was developed. This strategy led to a maximum pneumocandin B0 concentration of 2711 mg/L with a productivity of 9.05 mg/L/h, representing 34.67 and 6.47% improvements, respectively, over the best result achieved by the one-stage fermentation. Furthermore, G. lozoyensis accumulated glutamate and proline as compatible solutes to resist osmotic stress, and these amino acids also provided the precursors for the enhanced pneumocandin B0 production. Osmotic stress also activated ROS (reactive oxygen species)-dependent signal transduction by upregulating the levels of related genes and increasing intracellular ROS levels by 20%. We also provided a possible mechanism for pneumocandin B0 accumulation based on signal transduction. These findings will improve our understanding of the regulatory mechanisms of pneumocandin B0 biosynthesis and may be applied to improve secondary metabolite production.
KeywordsOsmotic stress Fed-batch Secondary metabolite Fungi Transcriptome analysis
This work was supported by the Natural Science Fund for Colleges and Universities in Jiangsu Province (No. 17KJB530006), the Natural Science Foundation of Jiangsu Province (BK20161048), the National Science Foundation of China (No. 21776136), the Program for Innovative Research Teams in Universities of Jiangsu Province (2015), the Top-notch Academic Programs Project of Jiangsu Higher Education Institutions (No. PPZY2015B155), and the Jiangsu Synergetic Innovation Center for Advanced Bio-Manufacture (No. XTE1854).
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Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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