木质纤维素生物预处理的现状：潜力、进展与挑战-外文翻译

1、译文:木质纤维素生物预处理的现状：潜力、进展与挑战摘要通过生化平台从木质纤维素中生产生物燃料和生化制剂的可行性在很大程度上取决于从植物细胞壁上的纤维素和半纤维素获得糖类的推进技术。本文概述了发展中的植物细胞壁结构生物预处理技术在从纤维素聚合物中进行糖的后续酶提取方面的成果和挑战。该技术已经成为了一个打破瓶颈的新选择。尽管由于许多固有的局限性没有引起多少注意，生物预处理还是由于其自身的许多优势而存在很大潜力，包括更环保、耗能更少、反应产生抑制剂更少、副产物更少等。在白蚁和白腐菌方面不断取得的科技成果为实现这些利益，发展新一代生物预处理技术提供了理论依据。本文综述了以木质素降解酶为主的酶系统，描述

2、了当前对微生物降解植物细胞壁的理解，对比了生物与化学的预处理过程。还对生物制浆的成果进行了总结，提供了一个未来生物预处理过程的发展方向。简介获得可再生燃料和化学制剂的唯一方式是通过利用绿色植物吸收太阳能，再以有机碳源的形式存储起来。大自然还开发了各种途径以额外的最小输入能量来利用和回收这些植物材料。这样做，大自然能够一直保持一个可持续发展的平衡的生态系统数百万年。如何利用木质纤维素的生物分解来进行生物燃料和生化生产是这些天然生物过程需要解决的主要障碍，他们往往最节能并且对环境产生的影响不大。随着化石燃料资源的衰退和对气候变化的担忧，发展生物质燃料和化学制剂显得愈发紧迫。例如，到2022年，每年

3、生产的360亿加仑可再生燃料中，生物燃料必须占到210亿加仑。未来生化和生物燃料发展的基础是生物质原料的供应。所有的类型中，木质纤维素、木质生物、作物残留物、草和藻类的生物质能含量是最丰富的。木质生物质是地球上最丰富的可再生生物资源，在地球上，每年可生产109200吨，其中只有3%用于诸如造纸工业的非食品领域。目前纤维素的消费量与谷物消费持平，是钢铁消费的3倍。为了既能将这些材料用于生产生物燃料又不与人类的粮食供应构成冲突，未来的生物炼制将以木质生物质原料为主。植物细胞壁（PCW定存储能源和有机碳的主要材料。PCW勺组成和结构决定了以它为原料来设计下游加工流程生产各种目标分子。植物由有序排列的

4、有壁细胞组成。细胞壁中含有不同比例的混合纤维素（Ca.40%）、半纤维素（Ca.20-30%）和（Ca.20-30%纤维素是一种葡萄糖单元由B-1,4-糖昔键联系在一起的线性聚合物。半纤维素是许多糖（木糖、甘露糖、半乳糖、阿拉伯糖、鼠李糖）单体的杂聚合物形成的随机非晶态结构。另一方面，木质素是由一个包含三种DPH（对香豆醇、松柏醇、芥子醇）的大分子单体交叉链接组成。木质纤维素是一个紧凑的复杂结构。其中一部分含有复杂晶体，和多糖紧密连接成的层状超细纤维形成的稳定剂来防止它们被水解酶和其他外部因素分解。以木材为例来解释其结构：通常，支持细胞死亡后的管腔可以作为水分运输的通道，其内层是一个成分未知的

5、异构混合部分，内层外面的次生壁可以进一步分为S3,S2,S1三个子层，三个子层都是由纤维素超细纤维嵌入在不同的半纤维素和木质素的一个非晶体混合物中组成的。纤维素的浓度最高的是S2子层，并且向中间层依次减少。富含半纤维素的S3层是最靠近导管的。中层的木质素浓度最高，然而，由于次生壁要厚得多，所以它包含了大部分的木质素（60-80%）。木质化是在初生壁发起的，邻近S1层中靠近形成层处进行纤维素沉积的细胞，然后形成于细胞间层和初生壁。在初生壁、结晶和无定形纤维素核心围绕着半纤维素聚合物。草类植物中，细胞间层、初生壁中含有更多的碳-碳键耦合形成的DPH,使之变成了一个有很多支链的聚合物。相比之下，伊O

6、-4耦合的DPH会在二级细胞壁中形成一个相对线性更强的聚合物。初生壁中高度支链化的木质素比次生壁中的线性木质素更能抑制细胞壁的降解。大多数生物过程集中于用糖作为能源和碳源通过发酵获得不同的产品。主要的糖单元是葡萄糖，在植物细胞壁结构中呈有界的共价纤维素聚合物。从物理化学加工中获得糖是一个重大的生物精炼的瓶颈。锁在纤维素和半纤维素聚合物中的糖单位是用于发酵生产生物燃料和生物化学制剂的唯一能源和碳源。纤维素聚合物的生化分解一般是由称为木纤维质酵素的纤维素酶完成的。由极其复杂而且种类繁多的纤维素复合而成的木质纤维素，有专门用来抵御攻击的结构。木质素和半纤维素的复杂的结构和疏水性的细胞壁可以防止酶与纤

7、维素聚合物接触。因此，木质素和半纤维素的结构需要被消减或修改为可以允许纤维素酶随意移动的自由空间。这通常是通过一个预处理的过程来解决的。我们越来越多的需要新的预处理方法。我们正在进入一个工业生物技术、合成生物学、代谢工程和系统生物学的新时代，这些新兴技术和学科提供新的工具微生物用以生产诸如碳氢化合物的先进生物燃料。在使用这些工具进行生物燃料生产方面的真正进步将是有限的，如果给这些微生物供应的糖仍然是一个主要障碍。考虑到自然已经通过进化创造了复合酶作为生物催化剂，它有能力通过选择性地断裂化学键之间的基本单位解开木质素分子的复杂结构，我们应该寻求利用类似的物理化学加工过程，利用木质素和半纤维素降解

8、酶实现在预处理中整合和糖化的终极目标。这些酶在传统的预处理之前或之后使用以实现减少，并最终取代热化学处理，从而减少整个预处理在大分子水平和简化工艺的严重影响。在可持续发展和能源效率的前提下，生物工艺由于其可以在自然环境下发生且环保的特点优于理化过程。基于此的生物预处理未来将吸引更多的关注。本文将在这个话题上提供一个全面的调查。本文将在目前生物预处理工艺的理论基础上，概述先进的知识，指出信息和技术的差距。最后，本文还提供了一些猜测，提出一些未来研究和发展方向。需要指出的是，理想的预处理过程需要木质素和半纤维素的解构。本文将，主要侧重于木质素降解。本文首先从木质素分解酶系统入手，其次是不同的微生物

9、如何分解木质素。对生物预处理和热化学预处理作出比较，然后提供生物制浆的应用实例，得出结论并展望未来。外文文献原文:StatusofBiologicalPretreatmentofLignocellulosics:Potential,ProgressandChallengesShulinChen,XiaoyuZhang,DeepakSingh,HongboYu,XueweiYangDepartmentofBiologicalSystemsEngineering,WashingtonStateUniversity,Pullman,WA99164.SchoolofLifeScience&Te

10、chnology,HuazhongUniversityofScience&Technology,Wuhan,Hubei,P.R.China,430074.AbstractThefeasibilityofproducingbiofuelsandbiochemicalsfromlignocellulosicbiomassviathebiochemicalplatformdependslargelyonadvancingtechnologiesobtainingsugarsfromthecelluloseandhemicellulosesoftheplantcellwalls.Thispap

11、erprovidesanoverviewonthemeritandchallengesrelatedtodevelopingbiologicalpretreatmentprocessesasanewalternativetobreakthebarriersoftheplantcellwallstructureforsubsequentenzymaticextractionofsugarsfromcellulosepolymer.Althoughhavingattractedlittleattentionduetomanyinherentlimitations,biologicalpretrea

12、tmenthasgreatpotentialbecauseofthemultiplebenefits,includingbeingmoreenvironmentallybenign,lessenergyintensive,lessinhibitorproduction,andco-productpossibilities.Increasingknowledgeontermiteandwhite-rotfungiprovidesinsightsindevelopinganewgenerationofpretreatmenttechnologiestorealizethesebenefits.Th

13、isreviewsummarizestheenzymesystemprimarilylignindegradingenzymes,describescurrentunderstandingofbiodegradationofplantcellwallsbymicroorganisms,comparesbiologicalversusthermochemicalpretreatmentprocesses.Thereviewalsosummarizestheprogressinbiopulping,suggestsafutureperspectivefordevelopingthebiologic

14、alpretreatmentprocesses.IntroductionTheonlywaytoobtainrenewabletransportationfuelsandchemicalsisthroughtheuseofplantbiomassthatstorestheinterceptedsolarenergyviaphotosynthesisintheformsoforganiccarbon.Naturehasalsodevelopedvariouspathwaysforutilizingandrecyclingtheseplantmaterialswithminimuminputofa

15、dditionalenergy.Indoingso,naturehasbeenabletomaintainasustainable,yetbalancedecosystemformillionsofyears.Thesenaturallyoccurringbiologicalprocessesshouldbeadoptedinaddressingmajorbarriersofbiorefinering-utilizationoflignocellulosicsforbiofuelsandbiochemicalproductionastheyareoftenthemostenergyeffici

16、entyetcreateslittleimpacttotheenvironment.Therehasbeenincreasingurgencyfordevelopingbiomassbasedfuelsandchemicalsastheconcernsoverclimatechangeincreasesandfossilfuelresourcesdecline.Forexample,the36billiongallonsofrenewablefuelsproductionperyearby2022ofwhich21billiongallonsmustbeadvancedbiofuels1.Th

17、ebaseforfuturebiofuelandbiochemicaldevelopmentisthesupplyofbiomassfeedstock.Amongalltypesofbiomass,lignocellulosics,thecellwallsoftrees,cropresidues,grasses2andalgae3ismostabundant.Lignocellulosicbiomassisthemostabundantrenewablebiologicalresourceonearth,withayearlyproductionof200109tons4,5,only3%of

18、whichisusedinnon-foodareas,suchasthepaperandpulpindustries6.Currentcelluloseconsumptionisthreefoldhigherthansteelconsumptionandequalscerealconsumption7.Astheuseofthesematerialsfortheproductionofbiofueldoesnotconstituteaconflictwiththeproducingfoodforhumanconsumption,lignocellulosicbiomasswillbethema

19、jorfeedstockforthefuturebiorefineries.Theplantcellwalls(PCW)aretheprimarymaterialswhereenergyandorganiccarbonarestored.ThecompositionandstructureofPCWdeterminesthedesignofthedownstreamprocessesusingPCWasrawmaterialstoproducevarioustargetmolecules.Plantconsistsofanorderlyarrangementofcellswithwallsco

20、mposedofvaryingamountsofamixtureofcellulose(ca.40%),hemicellulose(ca.20-30%)andlignin(ca.20-30%)8.CelluloseisalinearpolymerofD-glucoseunitslinkedby-1,4-glycosidicbonds.Hemicelluloseisheteropolymercontainingmanysugarmonomers(xylose,mannose,galactose,arabinose,andrhamnose)formingrandomamorphousstructu

21、res.Ligninontheotherhand,isacrosslinkedmacromoleculeconsistingofprimarilythreemonolignolmonomers(p-coumeraylalcohol,coniferylalcohol,andsinapylalcohol)thataremethoxylatedtovariousdegree.Lignincelluloseisacompact,inpartcrystallinecomplex,andpolysaccharidecomponentswhichformmicrofibersaredenselypacked

22、inlayersoflignin,protectingthemagainsttheactivityofhydrolyticenzymesandotherexternalfactors,servingasastabilizerofthecomplexstructure9.Suchastructurecanbe川ustratedusingwoodasanexample.Generally,thesupportingcellhasalumenafterthecellisdead,whichcanbemoreorlessemptyorfilledwithwater.Theinnerlayerisahe

23、terogeneousmixtureofcomponentsofunknowncomposition.Thesecondarywalloutsidetheinnerlayercanbefurtherdividedintothreesublayers(S3,S2,S1)allconsistingofcellulosemicrofibrilsembeddedinanamorphousmixtureofdifferenthemicellulosesandlignin10.TheconcentrationofthecelluloseishighestintheS2sublayerofthesecond

24、arywallanddecreasetowardsthemiddlelamella.TheS3layer,whichisnearthelumenisrichinhemicelluloses.Ligninhasthehighestconcentrationinmiddlelamella.However,sincethesecondarywallismuchthicker,itcontainsmostofthelignin(60-80%).Lignificationisinitiatedintheprimarywallsadjacenttothecornersofthecellundergoing

25、cellulosedepositionintheS1layersnearthecambiumandthenproceedsintheintercellularlayersandprimarywalls11.Intheprimarycellwall,crystallineandamorphouscellulosecoreissurroundedbyhemicellulosepolymer.Ingrass,themiddlelamellaandprimarywallcontainsmoreC-Ccouplingofmonolignolsintoahighlybranchedpolymer.Inco

26、ntrast,the-O-4couplingofmonolignolsleadstoarelativelylinearpolymerinthesecondarycellwall12.Thehighlybranchedligninsintheprimarycellwallsaremoreinhibitorytocellwalldegradationthanthelinearpolymerinthesecondarywalls13.Theessenceofconvertinglignocellulosicstofuelsandchemicalsistoobtainthedesirableformo

27、forganiccarbonmoleculesfromthePCWtobeusedeitherasprecursormoleculesorenergysourcesforthetargetedfuelproducts.Therearetypicallytwomajorplatformsforbiomassconversion.Thefirstoneisbiochemicalplatforminwhichvarioussugarmoleculesarefirstobtainedfromthebiomass.Thesugarsarethenusedbymicroorganismstobeconve

28、rtedsubsequentlytotargetfuelmoleculessuchasethanol.Whereastheotheristhermochemicalplatforminwhichthelignocellulosicsiseitherfirstbrokenintoamixtureofmoleculesorsimplemolecules.Someofthemolecules,uponseparationfromthemixture,canbeuseddirectlyasfuels;whereasthesimplemolecules,uponfurtherprocessing,can

29、besynthesizedasfuelmolecules.Forthepurposeofthispaper,ourdiscussionswillbelimitedtothebiochemicalplatform.Mostbiologicalprocessesfocusontheuseofthesugarsastheenergyandcarbonsourcethroughfermentationtoderivedifferentproducts.Thepredominantsugarunitisglucosesthatareboundedcovalentlyintheformofcellulos

30、epolymerwithintheplantcellwallstructure.ObtainingthesugarsfromthePCWisoneofthemajorbottlenecksinbiorefinering.Thesugarunitslockedinthecelluloseandhemicellulosepolymersarethesoleenergyandcarbonsourcesusedinfermentationforbiofuelandbiochemicalproduction.Thebreakdownofcellulosepolymerisofternaccomplish

31、edbiochemicallybycellulolyticenzymescalledcellulases14.Lignocellulose,anextremelycomplexandwidelyvaryingnanoscalecompositeofcellulose,iswelldesignedtoresistattack.Thecomplexofligninandhemicellulosesstructureandthehydrophobicityofthecellwallpreventenzymefromaccessingthecellulosepolymer.Thus,thestruct

32、ureoftheligninandhemicellulosesneedstobedegradedormodifiedtofreespaceforcellulasetoaccess.Thisisoftenaccomplishedthroughapretreatmentprocess.Thecurrentpretreatmenttechnologiesformakinganeasyaccessforthecellulaseenzymetocatalyzecellulosedegradationtosugarsarephysiochemicalinnature.Thepurposeofthesepr

33、ocessesistodegradethehemicellulosesorligninstructure.Hydrothermalprocessesincludesteamexplosion15,carbondioxideexplosion16,orhotwatertreatment17.Likewise,chemicalprocessesincludedilute-acidtreatment18,alkalitreatment19,organosolvprocessusingorganicsolvents20,ammoniafiberexplosion(''AFEX2),am

34、moniarecyclepercolation22,andozonolysis23.However,allthesepretreatmentmethodssufferinherentseriousdrawbacks.Thechemicalandphysicalmeansareoftenlimitedbythelackofselectivity.Althougheffective,theseprocessestendtodamagethebasicunitsofthesebiopolymersbyreactionstoformnewandoftenunwantedcompounds,suchas

35、thereleaseoftoxicandhazardouspollutants24,25.Currently,thereisnoanysinglepretreatmenttechnologythatisperfectlyacceptableintheconversionofbiomassintobiofuel.Thereisincreasingneedsfornewpretreatmentapproaches.Asweareenteringaneweraofindustrialbiotechnology,syntheticbiology,metabolicengineering,andsyst

36、embiologyprovidenewtoolstoengineermicrobestoproducedadvancedbiofuelssuchashydrocarbons.Therealadvancementinbiofuelproductionusingthesetoolswillbelimitedifthesupplyofsugarstothesemicroorganismsremainsamajorbarrier.Consideringthefactthatnaturehasbeencreatedthroughevolutionbiologicalcatalystsasamixture

37、ofenzymaticcomplexthatarecapableofunlockthecomplexstructureofligninmoleculesbyselectivelycleavingthechemicalbondsbetweenthebasicunits,weshouldseekexploitingthesimilarprocessesforbiologicallypretreatingthePCWwithlignindegradingenzymesandhemicellulosestoachievetheultimategoalofconsolidatingpretreatmen

38、tandsaccharification.Theseenzymeswouldbeappliedbeforeoraftertraditionalpretreatmenttominimizeand,eventually,replacethermochemicalprocesses,thuslesseningtheeffectsofoverallpretreatmentseverityatthemacromolecularlevelandsimplifyingprocessing.Intheinterestsofsustainabilityandenergyefficiency,biological

39、processissuperiortothephysiochemicalonesastheyoccursundernaturalenvironmentanddonotproducedisruptionsthatarenottolerablebytheenvironment.Basedonthebeliefthatsuchabiologicalpretreatmentwillattractmoreattentioninthefuture,thisreviewaimsatprovidingacomprehensivesurveyonthistopic.Itisxpectedthatthispape

40、rwillpresenttherationaleofbiologicalpretreatmentprocess,overviewthestateoftheartoftheknowledge,andidentifytheinformationandtechnologygaps.Finally,thereviewofferssomespeculationsandsuggestssomedirectionsforfutureresearchanddevelopment.Itneedstobepointedoutthatanidealpretreatmentprocessrequiresthedeco

41、nstructionofbothligninandhemicellulose.Thisreviewwill,however,focusprimarilyonlignindegradation.Thisarticlestartswithligninolyticenzymesystems,followedbyhowdifferentmicroorganismsdegradatedlignin.Comparisonsofbiologicalpretreatmentandthermochemicalpretreatmentarethenprovided,followedbybiopulpingasap

42、plicationexamples,andconcludedwithfutureperspectiveandchallenges.1. LigninolyticenzymesystemLignincanbedegradatedbyenzymesproducedbyvariousorganismsamongwhichwhiterotfungushasbeenfoundthemosteffective.Ligninbiodegradationbywhiterotfungiinvolvesvariousenzymes,andthemostsignificantthreearelaccases(ben

43、zenediol:oxygenoxidoreductase,EC),ligninperoxidases(LiPs,EC4),andmanganeseperoxidases(MnPs,EC3)26,27.LiPs,MnPs,andlaccasearephenoloxidaseswhichcatalyzesimilarreactions10.Theyoxidizephenoliccompoundstocreatephenoxyradicals.Non-phenoliccompounds,ontheotherhand,areoxidizedtothec

44、orrespondingcationradicals10.Obviously,notallthewhiterotfungicanproduceallthethreeligninolyticenzymes,dependingonthespeciesofwhiterotfungiandthetypeofsubstrates28,29.ThewhiterotfungusP.chrysosporiumevidentlycandegradeligninwithoutproducinglaccases30andproduceslaccasesinthepresenceofcellulose1.Pycnop

45、oruscinnabarinusisreportedtoproducelaccasesbutnotperoxidases2.PleurotusdryinusproducesMnPsatthepresenceoflignocellulosicsubstratebutnoenzymeproductioninsyntheticmedium3.2. ProcessesofbiologicaldeconstructionofplantcellwallsTherearemanywaysofplantdecayinnaturebydifferentorganismsinadditiontofungi.Alt

46、houghmanyofthemechanismsofPCWdegradationbythesesystemsarestillunknown,thereisnodoubtthatfurtherunderstandingoftheseprocesseswillprovidecriticalinsightintodevelopingnewgenerationofpretreatmentprocesses.3. Comparisonofbiologicalpretreatmentwithtypicalthermochemicalprocesses3.1. EffectivenessMainpurpos

47、eofthepretreatmentforlignocellulosesistodismantlethematrixstructureofligninandhemicellulosestomodifytheporesinthematerialtoallowcellulolyticenzymestopenetratethebarrierinthePCWtodegradecellulosepolymer15.Thus,thepretreatmentshouldbeeffectivetoavoiddegradationorlossofcarbohydrate,andavoidformationofi

48、nhibitoryby-productsforthesubsequenthydrolysisandfermentationanditmustbecost-effective11.3.2. EnergyconsumptionComparingtothebiologicalpretreatment,thermochemicalmethodstoconvertthelignocellulosicbiomassutilizeslargeamountofenergyintheformofheatandchemicals.Forexample,alkalineprocessessufferfromsili

49、cascalinginchemicalrecoverybecausemanyagriculturalfeedstocks,suchasriceandwheatstraw,haveveryhighsilicacontent.Thescalingproblemprohibitstherecoveryofalkalinechemicalsfrompretreatmentliquor10.Similarly,theuseofdiluteacidpretreatmentisnotentirelysatisfactoryforwoodybiomass,inparticularsoftwoods.There

50、quirementofsizereductionpriortothepretreatment10-12makesthediluteacidprocesslesssuitableforpretreatingfeedstockswithstrongphysicalintegrity,suchaswoodybiomass,bamboo,andgiantreed,becauseofthehigh-energyconsumptioninsizereduction.Theuseofconcentratedacidhasbeenusuallybasedonthesolubilizationofplantpo

51、lysachharidesin72%(w/v)H2SO4or41%(w/v)HClatlowtemperatures,followedbydilutiontoa3-6%acidconcentrationandheatingat100-120Cfor30-360min13.Although,closetothetheoreticalsugarproductioncanbeachievedthroughthisprocess,itinvolveshighcapitalinvestment,acidconsumptionandacidrecoverycosts14.3.3. Inhibitorsas

52、by-productsAmajordisadvantageofthermochemicalpretreatmentprocessesistheproductionofby-productsthatofteninhibitdownstreamprocesses.Duringthermochemicalandhydrothermalprocesses,someoftheglucosereleasedfromcelluloseisdegradedto5-hydroxymethylfurfural(HMF),levulinicacid,andformicacid.Likewise,thepentose

53、fromhemicelluloseisconvertedtofurfuralandformicacid.Duringsteamexplosion,ligninisprimarilydegradedthroughthehomolyticcleavageof,O-4etherandotheracid-labilelinkages,producingaseriesofcinnamylalcoholsderivativesandcondensationby-products14.Releaseoftheselowmolecularmasscompoundsgraduallyincreasestowar

54、dshigherpretreatmentseverities15.Theseproducts,alongwiththedegradedligninproductsandreleasedorganicacidsactasinhibitorsofenzymaticsaccharificationandethanolfermentation16,17(Figure1).Thedetoxificationstep,ifrequiredafterthethermochemicalprocessisverycostlyandoftenineffective12.Inaddition,thechemical

55、processesalonehaveseriousdisadvantagesintermsoftherequirementforthespecializedcorrosionresistantequipment,extensivewashing,andproperdisposalofthewastes.Biologicalpretreatmentusingwhiterotfungi,ontheotherhand,canavoidtheproductionoftheseunwantedby-products.3.4. ReactionrateAlthough,thebiologicalpretr

56、eatmentprocessisasafe,lowenergyrequiringprocessforlignocellulosicmaterialdisintegration,thetypicaldegradationprocessusingfungioccursinalongerincubationtime.Someofthebiologicalpretreatmenttimeofincubationandreleasedsugarpercentagehasbeentabulatedbelow.Hatakkaetal.19studiedthebiologicalpretreatmentofw

57、heatstrawby19fungalstrains.Incubatedatthe37°Cinthesolidstatefermentation,Pleurotusostreatuswasabletomake35%ofthestrawintoreducingsugarsin35daysofincubation(Table1).Forthesamesubstrat配hanerochaetesordidshowedthesimilarproductionratein28days18.Totalsugarreleasedwashigher;38.9%fromricehullsbyP.ost

58、reatusin60days.Pycnoporuscinnabarinustook28daystorelease35%totalreducingsugarsfromthewheatstraw15.Likewise,Tanaguchietal.16demonstratedthatthereleaseof83%celluloseand52%hemicellulosewasobtainedfromricestrawafter60days.Table1:Biologicaldegradationofvarioussubstratesbydifferentfungalstrainsandcontributioninthesugarreleaseaswellasligninloss.SubstrateMicroorganismTotalsugarLigninTimeReferencereleasedloss(days)WheatStrawPleurotus35%cNM3519ostreatusSapwoodofPhanerochaete71%hNM3217pinelogsgigantaeAspenPleurotus(Fr.)NM38%f5618(PopulusP.Karst.Speciestremuloi