毛木耳降解木质纤维素的研究

测定了毛木耳“沪毛一号”菌株瓶栽0—60天期间,其木屑基质中木素纤维素的降解和木质纤维分解酶活性的变化。结果表明,该菌能够同时降解木素、半纤维素和纤维素,尤以分解木素的能力为强(以各自相对百分含量减少计算),故毛木耳为白腐真菌。该菌的多酚氧化酶、羧甲基纤维素酶、滤纸纤维素酶和木聚糖酶的活性高峰均出现于菌丝体发育阶段,在子实体原基发生时(22天),羧甲基纤维素酶、滤纸纤维素酶、木聚糖酶的活性明显下降,在子实体发生后,该三种酶活性又复上升,直到头批耳成熟酶活仍处于较高水平。     

木质纤维素的定量测定及降解规律的初步研究

为了准确地测定稻草及其发酵物中纤维素、半纤维素、木质素的含量,通过差重法进行定量测定,并以此评价白腐菌株Pleurotus sapidus对稻草秸秆的降解状况,结果表明：利用差重法测定稻草发酵物中纤维素、半纤维索、木质素的百分含量是可行的,并能很好地评价白腐菌对稻草的降解规律,即降解过程中纤维素、半纤维素、本质素在前20d降解的很快,之后降解减缓,在50d内,纤维素被降解34．02％,半纤维素被降解56．29％,木质素被降解61．65％。     

白腐菌及黑曲霉所产的纤维素复合酶对稻草秸秆的生物降解

研究了白腐菌及纤维素复合酶对稻草秸秆的协同生物降解。结果表明,利用黄孢原毛平革菌固态发酵稻草秸秆的过程中,LiP和MnP的最大活力可以达到28.3U/g和12.6U/g,同时,秸秆中的木质素能被有效降解,但纤维素、半纤维素降解率较低。添加黑曲霉所产的纤维素复合酶能有效地促进秸秆腐熟程度。在接入白腐菌培养10天后,每克稻草添加3 IU纤维素酶液并酶解48h可以使稻草秸秆中纤维素降解53.8%,半纤维素降解57.8%,木质素降解44.5%,干物质损失46.3%。此时细胞壁出现大范围破损,整个组织变得松散,秸秆完全腐熟。     

三种白腐菌生物学特性与木质纤维素酶基因遗传多样性

以采自东北林业大学帽儿山实验林场的3种白腐真菌——木蹄层孔菌(Fomes fomentarius)、鲍姆鲍姆木层孔菌(Phellinus baumiibaumii)和火木层孔菌(Phellinus igniarius)为材料,用菌落直径测量法比较3种白腐菌在马铃署葡萄糖固体培养基上的生长速度,采用菌丝体干重法比较其在马铃署葡萄糖液体培养基中的生物量变化。结果显示:马铃薯葡萄糖固体培养基上3种白腐菌均为快速生长类型,其生长速度木蹄层孔菌火木层孔菌鲍姆鲍姆木层孔菌;马铃署葡萄糖液体培养基中生物量增长速度木蹄层孔菌鲍姆鲍姆木层孔菌火木层孔菌。用比色法测量其木质纤维素酶活性,结果显示:木蹄层孔菌产锰过氧化物酶和漆酶量较高,鲍姆鲍姆木层孔菌和火木层孔菌产木质素过氧化物酶量较高;木蹄层孔菌、鲍姆鲍姆木层孔菌和火木层孔菌3种白腐菌的3种主要木质素酶(锰过氧化物酶、漆酶和木质素过氧化物酶)的表达量,种间差异显著(F=3.75*、5.20**、3.01*),白桦木屑诱导处理与对照间差异显著(F=3.84*、4.19*、5.28*);两种主要纤维素酶(葡聚糖内切酶、葡聚糖外切酶)的表达量,种间差异不显著,受碳源影响作用显著(F=3.99*、4.04*)。筛选29对引物组合,对3种白腐菌几种主要木质纤维素酶基因进行TRAP-PCR分子标记检测,比较3菌种间遗传差异,扩增总条带数为357条,多态性条带数为255条,多态性条带的比例为71.43%,其中木质素降解酶基因总多态位点比率为73.77%,纤维素降解酶基因总多态位点比率为68.97%。3种白腐菌的木质纤维素降解酶基因在种间均存在较高的遗传差异。因此,特定基因的TRAP分子标记可以用于木腐菌的遗传变异分析。     

鸡腿菇对棉籽壳的降解与转化

栽培在棉籽壳培养基中的鸡腿菇具有较强的木质纤维素降解能力和较高的绝对生物学效率;木质纤维素是子实体生长阶段的主要碳源;CMC酶、FP酶和HC酶的活性变化与纤维素、半纤维素的降解速率正相关,漆酶的活性变化与木质素的降解速率正相关,而过氧化物酶的活性变化与木质素的降解速率没有相关性;淀粉酶在菌丝生长阶段活性较高,蛋白酶的活性高峰出现在子实体生长发育期。     

六种白腐菌预处理对毛白杨木材酶水解效果的影响

通过化学分析和酶水解试验,研究了不同的白腐菌对毛白杨的预处理效果及不同组分的降解对酶水解的影响。毛白杨木片经6种白腐菌预处理30d后,各组分都发生了降解,其中半纤维素的损失最为显著,Trametes ochracea C6888引起半纤维素降解率高达47.19%,其次是纤维素和酸不溶木素的降解。在后续酶水解过程中,6种白腐菌处理后的样品显示出不同的水解模式,菌株Trametes ochracea C6888、T. pubescens C7571和T. versicolor C6915预处理效果最为显著,还原糖得率在整个酶水解过程中一直高于对照,其中T. ochracea C6888在水解96h后还原糖得率达到15.93%,比未处理样品提高了25%。分析酸不溶木素降解率及半纤维素降解率与还原糖得率的关系发现,不同菌株在作用同一种基质时,预处理效果差异显著,木质素和半纤维素的脱除都会影响木质纤维素的酶水解。     

白腐菌在两种固体基质上的漆酶产量及同工酶活性比较研究

一株新分离的白腐菌Z1可在两种农业废弃物(麸皮和稻草秸杆)基质上生长并分泌漆酶,其中在麸皮基质上的漆酶产量比在稻草秸杆基质上的漆酶产量高出10倍左右,同时活性电泳显示Z1菌在麸皮基质上可产生3条漆酶同工酶,比在稻草秸杆基质上多1条,其活性也比在稻草秸杆基质中的漆酶活性高。     

白腐菌选择性降解竹基质中木质纤维素的研究

对竹基质白腐菌选择性降解进行了初步研究。结果表明,菌株B1对竹基质中木质素和半纤维素有明显的降解选择性。降解55 d木质素和半纤维素降解率分别达44.4%和47.1%;降解20 d降解选择性最好,木质素和半纤维素降解率选择系数分别是2.08和1.98。从FTIR图谱中木质纤维素相关谱峰(2 924、1 6351、6011、5101、165、1 045、666/cm等)的明显变化也可以得出相同结论。     

血红密孔菌高产漆酶菌株的筛选及其对烟梗的生物降解

白腐菌是目前已知的唯一能将木质素彻底降解的微生物,而漆酶在木质素分解过程中起着重要的作用,被广泛应用于农作物秸秆或甘蔗渣等多种类型生物质的生物预处理和生物降解。本研究利用白腐菌产漆酶发酵培养基对30株血红密孔菌Pycnoporus sanguineus菌株进行筛选,得到了多株漆酶高产菌株,并研究了血红密孔菌发酵粗酶液和菌丝对烟梗的生物降解条件。研究结果表明:血红密孔菌及其产生的漆酶表现出了对烟梗木质素较强的生物降解能力。在漆酶浓度为40U/mL、温度30℃、pH4.5的条件下处理24h,烟梗中木质素的降解率可达到50.4%,纤维素和半纤维素的降解率分别为17.5%和17.3%;漆酶浓度为5U/mL、温度30℃、pH4.5的条件下处理48h,木质素降解率可达到65.1%。血红密孔菌菌丝也表现出对烟梗较好的生物降解效果,接种培养7d后烟梗中木质素降解率可达30%以上,21d后木质素的降解率可达79.1%,而纤维素和半纤维素的降解率仅为20%和12%左右。本研究不但为生物质材料的生物预处理和生物降解提供了优质的白腐菌及漆酶资源,还为通过烟梗的生物预处理提高烟草梗丝和卷烟品质提供了重要参数,具有一定的应用前景。     

N+注入选育白腐菌及其降解油菜秸秆木质纤维素的研究

以白腐菌WY01为出发菌,利用N＋注入技术选育出一株遗传性状稳定的漆酶高产诱变菌株WY02,经过60 d的发酵培养,其产酶量由出发菌的13.75 U/g增加到52.5 U/g,即产酶量提高了2.82倍;诱变菌株WY02对油菜秸秆中的木质素、半纤维素和纤维素的降解率分别为54.1%,39.1%,32.8%,用红外光谱法（IR）分析经诱变菌株降解后的油菜秸秆中木质素官能团的变化,用于阐明诱变菌株对油菜秸秆中木质素的生物降解机制。结果表明：油菜秸秆经白腐菌诱变菌株降解后,其木质素含量明显降低。木质素与苯环相连的C=O键、木质素侧链上CH2结构以及木质素单体（紫丁香基和愈创木基）被部分降解,木质素的苯环结构遭到一定程度的破坏。     

白腐真菌对稻草秸秆的降解及其有关酶活性的变化*

以稻草秸秆加20%棉籽壳为培养基质,接种侧耳Z17、921、1024菌株,在不同生长阶段,测定培养物的主要化学成分和有关酶活的变化。结果表明,从接种到子实体形成,所试菌株培养物的纤维素、木质素等呈持续不断的下降趋势,水份、粗蛋白含量却逐渐升高。基质中漆酶酶活性在菌丝生长初期呈迅速上升趋势,后稍降低,而愈创木酚酶活性在菌丝生长初期及子实体形成时达到高峰,后有所降低或消失。     

贝壳状革耳菌和黄孢平革菌固体培养酶系比较

白腐菌黄孢平革菌(Phanerochaete chrysosporium) 与贝壳状革耳菌(Panus conchatus)在类似自然状态的固体培养条件下酶的分泌情况有 较大差异。P.conchatus和P.chrysosporium的主要木素降解酶分别是漆酶和锰过氧化物酶 ;两种菌均产生较高水平的木聚糖酶;P.conchatus在整个培养过程中所产生的内切葡 聚糖酶、微晶纤维素酶和纤维二糖酶活力均比P.chrysosporium相应酶的活力低得多, 尤其是内切葡聚糖酶。研究结果初步揭示了P.conchaus降解木素的主要酶系及选择性降 解木素的原因。     

油菜秸秆混合发酵降解菌的筛选

油菜秸秆含有大量木质纤维素,该类物质结构稳定,不易降解,限制了其工业化应用.通过对10株包括细菌、酵母菌和白腐真菌的菌株产酶能力和特性进行比较,并进行共同培养试验,筛选出5株可共同生长的木质纤维素降解菌BS09、BL、PC、TS和KS.通过对这5个菌株单独发酵降解油菜秸秆的能力考察,结果表明:PC对木质纤维素的降解能力...     

黄孢原毛平革菌对松木、稻草和芦苇去木质化作用的研究

为确定黄孢原毛平革菌对不同植物材料的去木质化作用,以pH、干物质重、半纤维素、纤维素和木质素为主要技术指标,比较黄孢原毛平革菌对松木、稻草和芦苇降解能力的差异。松木、芦苇在发酵过程中pH呈下降趋势,稻草呈上升趋势。在干物质重、半纤维素、纤维素降解率三个指标上皆为松木〈芦苇〈稻草,在木质素降解率上则为松木〈稻草〈芦苇,且差异显著。表明黄孢原毛平革菌对不同植物材料去木质化能力有较大差异,其中芦苇的木质素降解率为13％,是三种材料中最易于被去木质化的。     

Biological Pretreatment of Lignocellulosic Substrates for Enhanced Delignification and Enzymatic Digestibility

Sheer enormity of lignocellulosics makes them potential feedstock for biofuel production but, their conversion into fermentable sugars is a major hurdle. They have to be pretreated physically, chemically, or biologically to be used by fermenting organisms for production of ethanol. Each lignocellulosic substrate is a complex mix of cellulose, hemicellulose and lignin, bound in a matrix. While cellulose and hemicellulose yield fermentable sugars, lignin is the most recalcitrant polymer, consisting of phenyl-propanoid units. Many microorganisms in nature are able to attack and degrade lignin, thus making access to cellulose easy. Such organisms are abundantly found in forest leaf litter/composts and especially include the wood rotting fungi, actinomycetes and bacteria. These microorganisms possess enzyme systems to attack, depolymerize and degrade the polymers in lignocellulosic substrates. Current pretreatment research is targeted towards developing processes which are mild, economical and environment friendly facilitating subsequent saccharification of cellulose and its fermentation to ethanol. Besides being the critical step, pretreatment is also cost intensive. Biological treatments with white rot fungi and Streptomyces have been studied for delignification of pulp, increasing digestibility of lignocellulosics for animal feed and for bioremediation of paper mill effluents. Such lignocellulolytic organisms can prove extremely useful in production of bioethanol when used for removal of lignin from lignocellulosic substrate and also for cellulase production. Our studies on treatment of hardwood and softwood residues with Streptomyces griseus isolated from leaf litter showed that it enhanced the mild alkaline solubilisation of lignins and also produced high levels of the cellulase complex when growing on wood substrates. Lignin loss (Klason lignin) observed was 10.5 and 23.5% in case of soft wood and hard wood, respectively. Thus, biological pretreatment process for lignocellulosic substrate using lignolytic organisms such as actinomycetes and white rot fungi can be developed for facilitating efficient enzymatic digestibility of cellulose.     

Bioconversion and biotransformation of coir pith for economic production of Pleurotus florida: chemical and biochemical changes in coir pith during the mushroom growth and fructification

Coir pith represents ∼50% of the waste from the coir industries and was tested for its potential in serving as a growth substrate for the production of species of oyster mushroom, Pleurotus florida. Due to its high lignin (∼48%) content and amorphous powdery nature, coir pith supported poor mushroom mycelial growth and yields were considerably low (∼25% bioconversion efficiency). Pre-treating coir pith with hot water did not prove economical to produce the mushroom yields. Acid swelling and alkali delignification of coir pith though served to change the structure of coir pith; the mushroom yields were not improved. Amendment of coir pith with rice (Oryza sativa) straw and horse gram (Dolichos biflorus) plant residue tended to greatly modify the physical characteristics of the inoculated mushroom bed. Such a supplementation of coir pith growth substrate resulted in production of mushroom yields with 110–125% bioconversion efficiency. Implications of supplementing coir pith with rice straw/horse gram plant residue in terms of holocellulose:lignin ratio are discussed. Sensorially, the mushrooms so produced did not differ from that on rice straw, the economic growth substrate recommended for production of the mushroom yields on commercial scale. Changes in cellulose, hemicellulose and lignin contents of coir pith amended with rice straw were studied. Cellulase, hemicellulase and protease enzyme activities in the amended coir pith substrate showed a continuous increase from inoculation till the end of fructification, whereas laccase activity decreased during fructification, in consonance with decreased lignin degradation during fructification.     

Changes in biochemical constituents of paddy straw during degradation by white rot fungi and its impact on in vitro digestibility

Aims: To improve the digestibility of paddy straw to be used as animal feed by means of selective delignification using white rot fungi. Methods and Results: Solid state fermentation of paddy straw was carried out with some white rot fungi for 60 days. Different biochemical analyses, e.g. total organic matter (TOM) loss, hemicellulose loss, cellulose loss, lignin loss and in vitro digestibility, were carried out along with laccase, xylanase and carboxymethyl cellulase activity. The results were compared with that of a widely studied fungus Phanerochaete chrysosporium, which degraded 464 g kg^?1 TOM and enhanced the in vitro digestibility from 185 to 254 g kg^?1 after 60 days of incubation. Straw inoculated with Phlebia brevispora possessed maximum crude protein. Conclusions: All the tested white rot fungi efficiently degraded the lignin and enhanced the in vitro digestibility of paddy straw. Phlebia brevispora, Phlebia radiata and P. chrysosporium enhanced the in vitro digestibility almost to similar levels, while the loss in TOM was much lesser in P. brevispora and P. radiata when compared to P. chrysosporium. Significance and Impact of the Study: The study reflects the potential of P. brevispora and P. radiata as suitable choices for practical use in terms of availability of organic matter with higher protein value, selective ligninolysis and better digestibility.