Structural characteristics of humic-like acid from microbial

RESEARCHARTICLEStructuralcharacteristicsofhumic-likeacidfrommicrobialutilizationoflignininvolvingdifferentmineraltypesShuaiWang1,2&JunpingXu3&XiZhang4&YuWang1&JiayanFan1&LanLiu1&NanWang1&DianyuanChen1Received:18December2018/Accepted:3June2019/Publishedonline:20June2019#Springer-VerlagGmbHGermany,partofSpringerNature2019AbstractThispaperdeterminestheimpactoftwoclayminerals(kaoliniteandmontmorillonite)andthreeoxides(goethite,δ-MnO2,andbayerite)ontheelementalcompositionandFTIRspectraofhumic-likeacid(HLA)extractedfrommicrobial-mineralresidueformedfromthemicrobialutilizationoflignininliquidshakeflaskcultivation.Goethite,bayerite,andδ-MnO2showedhigherenrichmentcapabilitiesofCandO+SintheHLAthankaoliniteandmontmorillonite.GoethiteshowedthehighestretentionoforganicC,followedbybayerite,butkaoliniteexhibitedtheleastexchangeability.KaoliniteandmontmorilloniteenhancedmicrobialconsumptionofN,resultingintheabsenceofNinHLA.Afewaliphaticfractionswerepreferentiallygatheredonthesurfacesofkaoliniteandmontmorillonite,makingtheH/CratiosofHLAfromtheclaymineraltreatmentshigherthanthoseofHLAfromtheoxidetreatments.δ-MnO2wasconsideredthemosteffectivecatalystforabiotichumification,andgoethiteandbayeriterankedsecondandthirdinthisregard.Thistrendwasproportionaltotheirspecificsurfaceareas(SSAs).However,comparingtheeffectsofdifferenttreatmentsonthepromotionofHLAcondensationbyrelyingsolelyontheSSAofmineralswasnotsufficient,andotherinfluencingmechanismshadtobeconsideredaswell.Addi