Efficient secretory expression of phospholipase D for the high-yield production of phosphatidylserine and phospholipid derivates from soybean lecithin

Phospholipase D(PLD)is an essential biocatalyst for the biological production of phosphatidylserine and phospholipid modification.However,the efficient heterologous expression of PLD is limited by its cell toxicity.In this study,a PLD was secretory expressed efficiently in Bacillus subtilis with an activity around 100 U/mL.A secretory expression system containing the signal peptide SPEstA and the dual-promoter PHpaII-SrfA was estab-lished,and the extracellular PLD activity further reached 119.22 U/mL through scale-up fermentation,191.30-fold higher than that of the control.Under optimum reaction conditions,a 61.61%conversion ratio and 21.07 g/L of phosphatidylserine production were achieved.Finally,the synthesis system of PL derivates was established,which could efficiently synthesis novel PL derivates.The results highlight that the secretory expression system constructed in this study provides a promising PLD producing strain in industrial application,and laid the foundation for the biosynthesis of phosphatidylserine and other PL derivates.As far as we know,this work re-ports the highest level of extracellular PLD expression to date and the enzymatic production of several PL der-ivates for the first time.

Recent advances in metal-free CDs/g-C_(3)N_(4) photocatalysts:Synthetic strategies,mechanism insight,and applications

Carbon dots/graphite carbon nitride(CDs/g-C_(3)N_(4)),a novel composite photocatalyst,has shown great po-tential for applications in energy regeneration and environmental remediation owing to its following advantages:metal-free,low cost,easily tunable,and excellent photocatalytic performance.Hence,we reviewed the development of synthetic strategies,photocatalytic enhancement mechanisms,and pho-tocatalytic applications of CDs/g-C_(3)N_(4) in this study.First,the three composite strategies of CDs and g-C_(3)N_(4)-self-assembly,solvothermal,and calcination polymerization are outlined,and their advantages and disadvantages are described in detail.Moreover,the photocatalytic enhancement mechanism of the com-posite strategies was elucidated according to the variation trends of CDs/g-C_(3)N_(4) band structure,electronic properties,light absorption range,and interfacial charge transfer.Then,the applications of CDs/g-C_(3)N_(4) in hydrogen evolution,pollutant degradation,CO_(2) reduction,and bacterial disinfection in recent years are reviewed systematically.Finally,the current obstacles and future research directions of CDs/g-C_(3)N_(4) are discussed from the perspective of preparation technology and practical applications,respectively.