The ornithine-urea cycle involves fumaric acid biosynthesis in Aureobasidium pullulans var.aubasidani,a green and eco-friendly process for fumaric acid production

The current petroleum chemical methods for fumaric acid production can cause heavy pollution and global warming.In this study,the engineered strains of A.pullulans var.aubasidani were found to be suitable for green fumaric acid producer.Removal and complementation of the relevant genes showed only the ornithine-urea cycle(OUC)was involved in high level fumarate biosynthesis which was controlled by the Ca^(2+)signaling pathway.Removal of both the GOX gene encoding glucose oxidase and the PKS1 gene encoding the polyketide synthase for 3,5-dihydroxydecanoic acid biosynthesis and overexpression of the PYC gene encoding pyruvate carboxylase made the strain e-PYC produce 88.1±4.3 g/L of fumarate at flask level and 93.9±0.8 g/L of fumarate during the fed-batch fermentation.As a yeast-like fungal strain,it was very easy to cultivate A.pullulans var.aubasidani DH177 and their mutants in the bioreactor and to edit its genomic DNAs to enhance fumarate production.It was found that 2 mol of CO_(2) could be fixed during a maximal theoretical yield of 2 mol of fumarate per mole of glucose consumed in the OUC.Therefore,the OUC-mediated fumarate biosynthesis pathway in A.pullulans var.aubasidani was a green and eco-friendly process for the global sustainable development and carbon neutrality.

Porous carbon nanofibers derived from low-softening-point coal pitch towards all-carbon potassium ion hybrid capacitors

Potassium ion hybrid capacitors(PIHC)have promising applications in medium and large-scale energy storage systems due to their high energy/power density,abundant potassium resource and low cost.However,the slow kinetics of battery-type anodes originating from the large-size K+results in a mismatch between the two electrodes,rendering the modest energy density of PIHC.Herein,we first develop an electrospinning strategy to successfully synthesize fibrous precursor by using the HNO_(3)pre-oxidized low-softening-point coal pitch as the low-cost raw material.With further carbonization or KOH activation,the two types of carbon nanofibers(CNF)are fabricated as anode and cathode materials,respectively,towards the dual-carbon PIHC devices.Thanks to its threedimensional interconnected porous conducting network and large layer spacing,the resulted CNF anode material is endowed with high reversible capacities,excellent rate and long cycle stability.Meanwhile,the activated CNF cathode with a large surface area of 2169 m^(2)·g^(-1)exhibits excellent capacitive performance.A PIHC constructed with the two fibrous electrodes delivers an energy density of110.0 Wh·kg^(-1)at 200.0 W kg^(-1),along with a capacitance retention of 83.5%after 10,000 cycles at 1.0 A·g^(-1).The contribution here provides a cost-efficiency avenue and platform for advanced dual-carbon PIHC.