Targeting metabolic driving and minimization of by-products synthesis for high-yield production of D-pantothenate in Escherichia coli.

BACKGROUND: d-Pantothenate (DPA) is an important functional chemical that has been widely applied in healthcare, cosmetics, animal food, and feed industries. METHODS AND RESULTS: In this study, a high-yield DPA-producing strain was constructed by metabolic engineering strategies with targeting metabolic driving and by-products minimization. The metabolic driving force of push and pull was firstly obtained to improve the production of DPA via enrichment of precursor pool and synthetic pathway, accumulating 4.29 g L-1 DPA in shake flask fermentation. To eliminate the metabolic pressure on DPA production, an amino throttling system was proposed and successfully attenuated the synthesis of four competitive amino acids by a single-step regulation of gdhA. Further minimization of acetate was carried out by pta deletion, and utilization of ß-alanine was improved via enhancing its uptake system with producing 5.78 g L-1 DPA. Finally, the engineered strain produced 66.39 g L-1 DPA with ß-alanine addition in fermentor under fed-batch fermentation. CONCLUSION: This study paved a foundation for the industrial production of DPA.

Improvement of cordycepin production by an isolated Paecilomyces hepiali mutant from combinatorial mutation breeding and medium screening.

Cordycepin is a major bioactive compound found in Cordyceps sinensis that exhibits a broad spectrum of biological activities. Here a Paecilomyces hepiali OR-1 strain was initially isolated from plateau soil for the bioproduction of cordycepin. Subsequently, strain modification including 60Co γ-ray and ultraviolet irradiation were employed to increase the cordycepin titer, resulted in a high-yield mutant strain P. hepiali ZJB18001 with the cordycepin content of 0.61 mg/gDCW, showing a 2.3-fold to that from the wild strain (0.26 mg/gDCW). Furthermore, medium screening based on Box-Behnken design and the response surface methodology facilitated the enhancement of cordycepin yield to the value of 0.96 mg/gDCW at 25 °C for 5 days in submerged cultivation with an optimized medium composition. The high cordycepin yield, rapid growth rate and stable genetic characteristics of P. hepiali ZJB18001 are beneficial in terms of costs and time for the industrialization of cordycepin production.