Safety assessment of a novel marine multi-stress-tolerant yeast Meyerozyma guilliermondii GXDK6 according to phenotype and whole genome-sequencing analysis

The application of microorganisms as probiotics is limited due to lack of safety evaluation.Here,a novel multi-stress-tolerant yeast Meyerozyma guilliermondii GXDK6 with aroma-producing properties was identified from marine mangrove microorganisms.Its safety and probiotic properties were assessed in accordance with phenotype and whole-genome sequencing analysis.Results showed that the genes and phenotypic expression of related virulence,antibiotic resistance and retroelement were rarely found.Hyphal morphogenesis genes(SIT4,HOG1,SPA2,ERK1,ICL1,CST20,HSP104,TPS1,and RHO1)and phospholipase secretion gene(VPS4)were annotated.True hyphae and phospholipase were absent.Only one retroelement(Tad1-65_BG)was found.Major biogenic amines(BAs)encoding genes were absent,except for spermidine synthase(JA9_002594),spermine synthase(JA9_004690),and tyrosine decarboxylase(inx).The production of single BAs and total BAs was far below the food-defined thresholds.GXDK6 had no resistance to common antifungal drugs.Virulence enzymes,such as gelatinase,DNase,hemolytic,lecithinase,and thrombin were absent.Acute toxicity test with mice demonstrated that GXDK6 is safe.GXDK6 has a good reproduction ability in the simulation gastrointestinal tract.GXDK6 also has a strong antioxidant ability,β-glucosidase,and inulinase activity.To sum up,GXDK6 is considered as a safe probiotic for human consumption and food fermentation.

Migration Behavior of Impurity Iron in Silicon Melt Under Pulsed Electric Current

The impurity iron in silicon material will seriously affect the photoelectric conversion efficiency of silicon solar cells.However,the traditional silicon purification method has the disadvantages of long cycle,high energy consumption and serious pollution.In this study,an efficient and green pulsed electric current purification technology is proposed.The electromigration effect of iron elements,the current density gradient driving of iron phase,and the gravity of iron phase all affect the migration behavior of iron phase in silicon melt under pulsed electric current.Regardless of the depth of electrode insertion into the silicon melt,the solubility of iron in silicon decreases under the pulsed electric current,which helps to form the iron phase.At the same time,the iron phase tends to sink toward the bottom under the influence of gravity.When the electrode is shallowly inserted,a non-uniform electric field is formed in the silicon melt,and the iron phase is mainly driven by the current density gradient to accelerate sink toward the bottom.When the electrode is fully inserted,an approximately uniform electric field is formed in the silicon melt,and iron elements are preferentially migrated to the cathode by electromigration,forming iron phase sinking at the cathode.The study of impurity iron migration behavior in silicon melt under pulsed electric current provides a new approach for the purification of polycrystalline silicon.

Reconfiguring dual-phase structure with equal micro-hardness to achieve double strength with slight ductility sacrifice

The application of duplex stainless steel is severely restricted owing to its inherently low yield strength.A high yield strength of duplex stainless steel is required to address the lightweight issues and re-duce the emission of polluting gasses.Herein,excellent mechanical properties of duplex stainless steel were achieved using a flash annealing treatment to obtain austenite and ferrite phases with equal hard-ness,and the yield strength doubled without a substantial ductility sacrifice.The improvement in yield strength was caused by the grain boundary strengthening(a contribution of 60%to the yield strength)and hetero-deformation-induced strengthening(remaining 40%contribution to the yield strength)owing to the significant difference in the strain partitioning between the two phases.The high strain-hardening capability ensured ductility without a significant decrease;this correlated to the multiple microstruc-ture deformation mechanisms.These mechanisms included the synergetic deformation of the ferrite with dislocation cell formation and austenite accompanied by the sequential appearance of dislocation accumulation,stacking faults,and deformation-induced nanoscale twins and martensite.Deformation-induced multilevel stacking fault networks and high-density Lomer-Cotterll locks further improved the strain hardening response by enhancing the hetero-deformation behavior of austenite and ferrite.

Altering the Residual Stress in High-Carbon Steel through Promoted Dislocation Movement and Accelerated Carbon Diffusion by Pulsed Electric Current

Residual stress in high-carbon steel affects the dimensional accuracy, structural stability, and integrity of components. Although the evolution of residual stress under an electric field has received extensive attention, its elimination mechanism has not been fully clarified. In this study, it was found that the residual stress of high-carbon steel could be effectively relieved within a few minutes through the application of a low density pulse current. The difference between the current pulse treatment and traditional heat treatment in reducing residual stress is that the electric pulse provides additional Gibbs free energy for the system, which promotes dislocation annihilation and carbon atom diffusion to form carbides, thus reducing the free energy of the system. The electroplastic and thermal effects of the pulse current promoted the movement of dislocations under the electric field, thus eliminating the internal stress caused by dislocation entanglement. The precipitation of carbides reduced the carbon content of the steel matrix and lattice shrinkage, thereby reducing the residual tensile stress. Considering that a pulsed current has the advantages of small size, small power requirement, continuous output, and continuously controllable parameters, it has broad application prospects for eliminating residual stress.

Regulating the recrystallized grain to induce strong cube texture in oriented silicon steel

Cube texture contains two easy magnetization directions<001>parallel to rolling and transverse direction,respectively,which is the most ideal magnetic texture suitable not only for transformers but also for rotating machines.In this study,a strong cube texture with ODF density of 50.73 mrd was successfully obtained by regulating the recrystallized grain orientation using cross-rolling and pulsed electric current,compared to conventional thermal annealing(the average cube texture intensity is~10 mrd in lots of latest studies).Cross cold rolling process intentionally"created"metastable deformed cube orientation in oriented silicon steel and the specific recrystallization texture rotation path was identified under pulsed electric current in 5 min:{114}<261>→{114}<151>→{114}<041>→{001}<150>→{001}<010>.The cube-oriented grains were induced by pulsed electric current(800℃)and rapid heating(51.9℃/s,750℃),while the cube grains were observed in the annealed samples at the high temperature(1060℃).Recrystallized grain size of pulsed samples is about twice that of the annealed sample.This phenomenon is considered that the concurrent effects of electron wind force and Joule heating affected the nucleation,growth and rotation of cube grains by reducing the nuclear barrier,producing higher grain boundary mobility and structural evolution towards a state with lower electrical resistance.This idea of current-controlled texture is worthy of popularization in more materials and the realization of an electromagnetic field to crystal orientation selection is an interesting topic.

Synergistic Balance of Strength and Corrosion Resistance in Al-Mg-Er Alloys

High-strength,corrosion-resistant,and lightweight Al-Mg alloys perform an important function in harsh coastal service environments.Corrosion resistance is generally inversely correlated with strength;hence,it is difficult to simultaneously optimize both.In this study,a low-magnesium Er-containing Al-based alloy that is stronger and more corrosion resistant than Al-based alloys have been reported.The alloy contains Er,and the precipitation of Al3 Er within a face-centered cubic matrix is obtained by a series of smelting-casting,heat treatment,and rolling processes.It is presumed that the strengthening phase of Al3 Er pinning dislocations improves alloy strength.It also increases the recrystallization temperature of cold-rolled matrix and induces the distribution of small-angle grain boundaries,thus allowing the alloy to achieve excellent environmental corrosion resistance.As a result,strength and corrosion resistance are simultaneously improved.

Optimization of <001> grain gene based on texture hereditary behavior of magnetic materials

Since the intrinsic properties of materials are determined by the properties and arrangement of atoms,including crystal structure and defects,there is a strong analogy between material genes and biological genes.Therefore,improving the performance of materials by optimizing their genes is a new idea of material upgrading.The<001>orientation texture is closely related to the magnetic properties of soft magnetic materials.We designed and experimentally demonstrated a gene optimization in an important soft magnetic material by electric current.The reduction of grain boundary hopping energy barrier caused by the distribution of electromagnetic field promoted<001>orientation grain nucleation and growth,which directly improved the initial<001>orientation grain gene,and the inheritance of<001>orientation texture was used to control the formation of recrystallization texture.Therefore,it is possible to utilize the gene optimization technique in many materials upgrading such as metal materials and biological materials according to the differences in electromagnetic properties of microstructures.