简介：GlowdischargeplasmanitridingofAISI304austeniticstainlesssteelhasbeencar-riedoutfordifferentprocessingtimeunderoptimumdischargeconditionsestablishedbyspectro-scopicanalysis.ThetreatedsampleswereanalysedbyX-raydiffraction(XRD)toexplorethechangesinducedinthecrystallographicstructure.TheXRDpatternconfirmedtheformationofanexpandedaustenitephase(γN)owingtoincorporationofnitrogenasaninterstitialsolidsolu-tionintheironlattice.AVickersmicrohardnesstesterwasusedtoevaluatethesurfacehardnessasafunctionofindentationdepth(μm).Theresultsshowedclearevidenceofsurfacechangeswithsubstantialincreaseinsurfacehardness.

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简介：ToobtainthermotolerantmutantsofG.oxydans,whichcanenhancethetransformationrateofL-sorboseto2-Keto-L-gulonate(2-KLG)at33℃inatwo-stepprocessofvitaminCmanufacture,ionbeamwasusedasamutationsource.GluconobacteroxydansGOandBacillusmegateriumB0wereusedinthisstudy.TheoriginalstrainGluconobacteroxydansGOwasmutatedbytheheavyionimplantationfacilityattheInstituteofPlasmaPhysics,ChineseAcademyofSciences.SeveralmutantsincludingGluconobacteroxydansGI13wereisolatedandcoculturedwithBacillusmegateriumB0at33℃inshakingflasks.TheaveragetransformationrateofthenewmixedstrainGI13-B0inpergram-moleculereached94.4%aftersevenpassagesinshakingflasks,whichwasincreasedby7%whencomparedwiththeoriginalmixedstrainG0-B0(GluconobacteroxydansG0andBacillusmegateriumB0).Moreover,thetransformationrateofI13B0wasstableat94%attemperaturesrangingfrom25℃to33℃,whichwouldbeofmuchvalueinreducingenergyconsumptioninthemanufactureofL-ascorbicacid,especiallyintheseasonofsummer.Toclarifysomemechanismofthemutation,thespecificactivitiesofL-sorbosedehydrogenaseinbothG0andGI13wereestimated.

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