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19,20-Epoxy-cytochalasin Q (B5A) is a cytochalasin with a wide range of biological activities, which can be produced byXylaria sp.sof11, a strain isolated from the seafloor of the northern South China Sea. Since the low titer of B5A has greatly limited its further studies, we have systematically conducted the fermentative optimization for B5A production in this article. The effects of major medium components, including the carbon and organic nitrogen sources, as well as of the concentration of sea salt, were respectively investigated through single-factor experiments. As a result, sucrose and fish meal were determined to be the key factors affecting the production of B5A. Then three important variables, sucrose, fish meal, and filling volume, were screened out by the Plackett–Burman (PB) design. The optimal level of these variables was further confirmed by response surface analysis. The final formulated medium was set as 35.2 g/L sucrose and 18.0 g/L fish meal, with filling volume of 34.6 mL, which could afford 440.3 mg/L production of B5A, approximately 4.4-fold higher than that in the original medium. The significantly improved productivity of B5A will facilitate the subsequent mechanistic and clinical studies of B5A. [ABSTRACT FROM PUBLISHER]

Coenzyme Q 10 (CoQ 10 ) is an important component of the respiratory chain in humans and some bacteria. As a high-value-added nutraceutical antioxidant, CoQ 10 has excellent capacity to prevent cardiovascular disease. The content of CoQ 10 in the industrial Rhodobacter sphaeroides HY01 is hundreds of folds higher than normal physiological levels. In this study, we found that overexpression or optimization of the synthetic pathway failed CoQ 10 overproduction in the HY01 strain. Moreover, under phosphate- limited conditions (decreased phosphate or in the absence of inorganic phosphate addition), CoQ 10 production increased significantly by 12% to220 mg/L, biomass decreased by 12%, and the CoQ 10 productivity of unit cells increased by 27%. In subsequent fed-batch fermentation, CoQ 10 production reached 272 mg/L in the shake-flask fermentation and 1.95 g/L in a 100-L bioreactor under phosphate limitation. Furthermore, to understand the mechanism associated with CoQ 10 overproduction under phosphate- limited conditions, the comparatve transcriptome analysis was performed. These results indicated that phosphate limitation combined with glucose fed-batch fermentation represented an effective strategy for CoQ 10 production in the HY01. Phosphate limitation induced a pleiotropic effect on cell metabolism, and that improved CoQ 10 biosynthesis efficiency was possibly related to the disturbance of energy metabolism and redox potential., (© 2019 Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.)