复合菌系GF-20低温降解玉米秸秆过程中群落演替与理化特性

【背景】秸秆的生物降解具有高效率和环保等特点而备受关注。【目的】明确复合菌系GF-20秸秆降解过程中发挥重要作用的功能微生物类群及其与降解特性的关系。【方法】将复合菌系GF-20在10°C条件下恒温培养,定期取样测定其生长特性及秸秆分解特性,利用MiSeq高通量测序技术,分析不同降解时期复合菌系的群落结构变化规律。【结果】复合菌系GF-20在接种后1 d内进入对数生长期,pH值迅速下降至6.98,总糖含量迅速降低至0.22 mg/mL;3 d后体系可溶性化学需氧量降低至4.77 g/L,氧化还原电位迅速降低至-303 m V,并高效分泌纤维素酶;培养15 d时玉米秸秆降解率为31.97%,木质素、纤维素和半纤维素降解率分别为32.30%、44.85%和43.84%。在玉米秸秆降解过程中,降解初期(2、5 d)的优势菌属为Cellvibrio (29.55%)、Chryseobacterium (7.35%)、Hydrogenophaga(3.86%)和Pseudomonas(3.42%);降解中期(7、10d)的优势菌属为Azospirillum(9.92%)、Rhizobium (6.99%)、Nubsella (5.06%)和Stenotrophomonas (3.37%);降解后期(12、15 d)的优势菌属为Taibaiella (13.82%)、Pleomorphomonas (13.69%)、Flavobacterium (14.89%)、Cellulomonas(7.18%)、Devosia(7.36%)、Pedobacter(4.32%)和Sphingomonas(2.23%)。【结论】明确了复合菌系GF-20在不同降解时期微生物群落结构演替规律以及秸秆降解特性动态变化,为复合菌系的合理化利用提供理论依据。     

降解吡啶复合菌系MD1的筛选、降解特性及代谢途径

【目的】为筛选吡啶高效降解复合菌系，促进高浓度吡啶废水的降解。本研究围绕吡啶降解复合菌系的筛选、降解特性及代谢途径，旨在获得吡啶高效降解复合菌系，为高浓度吡啶废水微生物降解及完全矿化提供理论依据和技术支撑。【方法】以吡啶为唯一碳氮源从某农药废水处理系统好氧活性污泥中筛选得到一个吡啶高效降解复合菌系MD1。采用16S rRNA高通量测序技术探究了MD1的群落结构及多样性，通过单因素实验考察了MD1的降解特性，利用气相色谱-质谱联用仪对MD1降解吡啶的代谢产物进行了初步检测与鉴定，推测吡啶可能的降解途径。【结果】结果显示，在温度30 ℃、pH 8.0、NaCl浓度0.1%的最佳条件下培养72 h，MD1对初始浓度1 400 mg/L的吡啶降解率为98.44%±0.27%。在属水平上，MD1主要由副球菌属(Paracoccus sp.)、布鲁氏菌属(unclassified_Brucellaceae)、无色杆菌属(Achromobacter sp.)等组成。由代谢产物检测结果初步推测MD1对吡啶的代谢途径为吡啶→烟酸→6-羟基烟酸→2,5-二羟基吡啶→N-甲酰基马来酰胺酸→马来酰胺酸→马来酸→CO₂+H₂O。【结论】研究筛选得到一个可高效降解吡啶、降解性能稳定的复合菌系MD1。解析了MD1的微生物组成多样性和群落结构，推测了MD1可能的代谢途径，研究结果丰富了吡啶降解微生物资源。     

饲喂玉米秸秆的白星花金龟幼虫肠道细菌多样性

【目的】分析比较饲喂玉米Zea mays L.秸秆的白星花金龟Protaetia brevitarsis幼虫中肠、后肠中细菌群落结构,挖掘肠道细菌在白星花金龟消化秸秆中的功能。【方法】分别提取健康白星花金龟3龄幼虫10个样品(5个中肠内含物、5个后肠内含物)肠道细菌总DNA,利用Illumina HiSeq技术对白星花金龟幼虫中肠和后肠细菌的16S rDNA V4区序列进行测序,统计样品操作分类单元(operational taxonomic units,OTUs)数量,分析物种丰度、α多样性和β多样性,并将细菌群落信息映射到KEGG基因组数据库,进行细菌群落功能挖掘。【结果】共获得白星花金龟3龄幼虫肠道细菌1 062 897高质量reads,聚类为2 441个OTUs,总共注释到27个门,51个纲,77目,168科,326属。在属的分类阶元上,中肠中以假单胞菌属Pseudomonas为最优势属,后肠中以脱硫弧菌属Desulfovibrio为最优势属。α多样性分析表明,后肠群落多样性更丰富;β多样性分析结果显示,后肠微生物群落更稳定。细菌群落功能分析结果显示,中肠、后肠细菌群落都含有降解秸秆相关的酶系,其中,中肠降解木质素相关的通路更丰富,后肠降解纤维素的酶更多。【结论】采用Illumina HiSeq测序技术明确了饲喂玉米秸秆的白星花金龟幼虫中肠、后肠细菌群落结构与特点,进一步发现了肠道细菌在白星花金龟秸秆消化过程中发挥的作用,相关研究结果将为白星花金龟消化秸秆的机制深入研究提供参考,为我国秸秆资源化利用提供新思路。     

~(13)C-标记秸秆添加对DNA稳定性同位素探针试验结果的影响

【目的】稳定性同位素探针技术(stable isotope probing,SIP)是采用稳定性同位素示踪复杂环境中具有代谢活性微生物的有力工具。然而,在近期利用SIP技术的研究当中,我们发现~(13)C-标记物对试验本身有一定程度影响。例如研究土壤秸秆降解微生物,需将~(13)C-标记作物秸秆添加到土壤,利用微域培养实验和DNA-SIP技术解析主导降解微生物物种。但是~(13)C秸秆的添加以及不同土壤肥力水平是否会影响土壤微生物群落有待商榷。【方法】本研究采集江西鹰潭红壤试验站3种施肥处理(Control、NPK、OM)水稻土壤,分别添加自然丰度(12C)和~(13)C-标记的高丰度水稻秸秆,进行微域培养试验,研究两种秸秆添加下的响应物种以及不同丰度C对生物质气体的累积排放、细菌a-多样性以及群落结构的影响。【结果】研究发现,3种施肥土壤下,2种丰度秸秆处理间C累计排放无差异。但是,寡营养条件(Control)下,~(13)C-标记秸秆处理的细菌a-多样性高,12C秸秆处理群落异质性高,稳定性较差,无差异性物种;与~(12)C秸秆处理相比,富营养条件(NPK和OM)下,~(13)C-标记秸秆处理的细菌a-多样性和群落结构无差异,但存在差异物种,主要集中于变形菌门和稀有物种。【结论】本研究的结果表明~(13)C标记秸秆对微生物群落有一定影响,因此在后续的SIP试验中,高丰度秸秆虽可被用来作为标记底物,但需慎用。     

解糖热解纤维素菌F32降解未预处理秸秆及产纤维素酶特性分析

【目的】明确极端嗜热厌氧木质纤维素降解菌解糖热解纤维素菌F32代谢特征,并分析其产酶特性。【方法】使用细胞计数法绘制菌株的生长曲线,使用离子色谱及气相色谱进行产物和残糖量分析,以DNS法及对硝基苯酚法检测菌株胞外蛋白的酶活性。【结果】解糖热解纤维素菌F32在以葡萄糖、微晶纤维素和未经预处理小麦秸秆为碳源时生长状况优于解糖热解纤维素菌DSM 8903。在以葡萄糖为碳源进行培养时,与菌株DSM 8903相比,菌株F32具有产乳酸较多,而产氢气较少的特点。在以微晶纤维素和未经预处理小麦秸秆为碳源进行培养时,与菌株DSM 8903相比,菌株F32胞外蛋白具有较高的内切纤维素酶活性和木聚糖酶活性。【结论】解糖热解纤维素菌F32表现出较强的木质纤维素降解能力,其与DSM 8903的产物组成及胞外蛋白的酶活性具有明显差异。     

浓香型白酒两个产区窖泥微生物群落结构分析

【目的】探索浓香型白酒两个典型产区窖泥微生物群落结构和多样性,分析窖泥微生物群落地域特征及对白酒风格形成的影响。【方法】分别提取四川和安徽两个产区窖泥样品总DNA,应用PCR-ARDRA和16S rRNA基因克隆测序技术对两个产区窖泥细菌和古菌进行研究。【结果】两个浓香型白酒产区窖泥细菌丰富,包括:厚壁菌门(Firmicute)、拟杆菌门(Bacteroidetes)、绿弯菌门(Chloroflexi)、互养菌门(Synergistetes)、Armatimonadetes类群和未分类细菌(Unclassified bacteria)。两个产区窖泥绝对优势种群均为厚壁菌门中梭菌纲(Clostridia)细菌,在四川产区窖泥中检出较多的互营单胞菌属(Synthrophomonas)和紫单胞菌属(Petrimonas)。古菌的群落组成较为简单,主要是甲烷囊菌属(Methanoculleus)、甲烷八叠球菌属(Methanosarcina)、甲烷鬃菌属(Methanosaeta)和甲烷杆菌属(Methanobacterium)4个产甲烷古菌类群,四川产区窖泥优势古菌为甲烷囊菌和甲烷八叠球菌,安徽产区则为甲烷八叠球菌属和甲烷鬃菌。【结论】四川和安徽两个产区窖泥微生物的16S rRNA基因克隆文库系统地反映了两者微生物群落的相似性和差异性,对揭示浓香型白酒两个产区的酒体风格差异形成有一定的参考价值。     

外源纤维素诱导明显影响微生物土壤结皮细菌群落结构

【目的】微生物土壤结皮(Microbial soil crusts, MSCs)对于遏制土壤荒漠化、恢复荒漠地区生态环境起着重要作用。MSCs中的微生物, 特别是纤维素降解菌, 起着稳固、修复生态环境的功能。外源纤维素诱导是全面认识MSCs中纤维素降解细菌的多样性及其在MSCs形成和发展中的作用的重要途径。【方法】通过对微生物土壤结皮分别添加小麦秸杆(麦秸)、锯末木屑两类纤维素材料进行诱导, 以PCR-DGGE方法分析细菌群落变化。【结果】外源纤维素, 特别是麦秸的添加会迅速提高MSCs中细菌丰富度及多样性, 将细菌丰富度提高约66.7%, Shannon-Weiner指数提高约15.8%; 相同处理的样品聚类位置较近, 说明纤维素对于MSCs细菌菌群变化起主导作用; 细菌群落结构组成在添加纤维素诱导后发生了变化, 麦秸诱导样品与同时期对照样品差异最大, 但各样品中Firmieutes和Alphaproteobacteria始终为优势类群; 所得DGGE条带序列中有13条与纤维素降解菌序列同源性相近, 他们所代表的细菌很可能具有纤维素降解能力, 其中厌氧性的梭菌属(Clostridium)所占比例最大, 约为46.1%, 其次为芽孢杆菌属(Bacillus), 约占30%; 纤维素降解过程中, 诱导增加了MSCs发育有重要作用的一些类群如Microcoleus vaginatus和一些Alphaproteobacteria类群细菌等的丰度和多样性, 它们中有的可通过分泌多糖物质等增强土壤颗粒黏结、有的可以其固碳或固氮等能力提高土壤营养水平。【结论】为认识外源纤维素诱导MSCs细菌群落结构的变化规律, MSCs中纤维素降解细菌的多样性及纤维素降解细菌对MSCs形成和发展的作用提供了基础, 同时也为恢复荒漠生态系统实践方法提供了理论依据。     

降解尿酸乳酸菌复合菌系的筛选与菌株组合提升降解效果

【背景】高尿酸症由血液中尿酸含量明显升高而导致,利用乳酸菌对人体的益生作用缓解高尿酸血症越来越受到关注。【目的】获得具有降解尿酸能力的乳酸菌复合菌系与纯培养菌株。【方法】以泡菜为样品来源,以尿酸为底物,采用MRS培养基筛选降解尿酸的乳酸菌复合菌系,通过高效液相色谱法测定复合菌系对尿酸的降解能力。【结果】得到一组乳酸菌复合菌系,当培养温度为37 °C、pH值为6.20、静置培养72 h后复合菌系对尿酸的降解率为12.08%;通过优化培养条件,当该菌系在以牛肉膏为单一氮源、初始pH值为5.00、温度为35 °C的条件下培养72 h,尿酸降解率上升至17.19%,降解率比优化前提高了42.3%;从该菌系中分离出两株具有尿酸降解能力的菌株UA-1与UA-2,它们的尿酸降解率分别为10.85%和8.65%;通过形态学观察和16S rRNA基因序列分析,经鉴定两株菌均为布氏乳杆菌(Lactobacillus buchneri)。将两株单菌组合降解尿酸试验发现,UA-1与UA-2比例为2:1的尿酸降解率为20.2%,比原复合菌系的降解能力提高了67.22%。【结论】研究证明了乳酸菌复合菌系对尿酸的降解能力优于单个菌株,为后续利用乳酸菌复合菌系应用提供了数据支持。     

复合菌系降解纤维素过程中微生物群落结构的变化

为明确高效纤维素降解复合菌系降解过程中微生物群落结构的变化规律及关键的降解功能菌,利用该复合菌系对滤纸和稻秆进行生物处理,通过底物降解、微生物生长量、发酵液pH的变化情况,选择不同降解时期复合菌系提取的总DNA进行细菌16S rRNA基因扩增子高通量测序。通过分解特性试验确定在接种后培养第12、72、168 h分别作为降解初期、高峰期、末期。该复合菌系分别主要由1个门、2个纲、2个目、7个科、11个属组成。随着降解的进行,短芽胞杆菌属Brevibacillus、喜热菌属Caloramator的相对丰度逐渐降低;梭菌属Clostridium、芽胞杆菌属Bacillus、地芽胞杆菌属Geobacillus、柯恩氏菌属Cohnella的相对丰度逐渐升高;解脲芽胞杆菌属Ureibacillus、泰氏菌属Tissierella、刺尾鱼菌属Epulopiscium在降解高峰期时相对丰度最高;各时期类芽胞杆菌属Paenibacillus、瘤胃球菌属Ruminococcus的相对丰度无明显变化。上述11个主要菌属均属于厚壁菌门,具有嗜热、耐热、适应广泛pH、降解纤维素或半纤维素的特性。好氧型细菌是降解初期的主要优势功能菌,到中后期厌氧型细菌逐渐增多,并逐步取代好氧型细菌成为降解纤维素的主要细菌。     

降解水稻秸秆兼抑制水稻纹枯病菌多功能复合菌系的构建

目的针对稻草直接还田需要,构建能够高效降解水稻秸秆同时又能抑带l水稻纹枯病菌的多功能复合菌系。方法通过将具有高效降解纤维素的天然复合菌群与具有抑制水稻纹枯病菌效果的菌株组合,构建多功能复合菌系;采用失重法检测该复合菌系对水稻秸杆的腐解作用,荧光定量PER法检测其对水稻纹枯病菌的抑制效果。结果成功地构建了一组多功能复合菌系,腐解12d后,水稻秸秆干物质总失重率为41．4％,其中半纤维素降解率为59．5％,纤维素降解率为52．5％,木质素降解率为15．3％,腐解过程中平均CMC酶活为8．1IU／g。该复合菌系对水稻纹枯病菌的抑制效果明显,发酵40d后对水稻纹枯病菌的抑制率为27．1％,对照组抑制率为2．7％。结论该复合菌系能高效降解水稻秸秆,同时又能较好地抑制水稻纹枯病菌,适宜在水稻秸秆直接还田过程中使用。     

Regioselective acylation of several polyhydroxylated natural compounds by Candida antarctica lipase B

Regioselective acylation of four polyhydroxylated natural compounds, deacetyl asperulosidic acid (1), asperulosidic acid (2), puerarin (3) and resveratrol (4) by Candida antarctica Lipase B in the presence of various acyl donors (vinyl acetate, vinyl decanoate or vinyl cinnamoate) was studied. Compounds 1, 2 and 4 were regioselectively acetylated with vinyl acetate to afford products, 3'-O-acetyl-10-O-deacetylasperulosidic acid (1a), 3',6'-O-diacetyl-10-O-deacetylasperulosidic acid (1b), 3'-O-acetylasperulosidic acid (2a), 3',6'-O-diacetylasperulosidic acid (2b), 4'-O-acetylresveratrol (4a), respectively, with yields of 22 to 50%, while reactions with vinyl decanoate and vinyl cinnamoate were slow with lower yields. Compound 3 was readily acylated with all three acyl donors and quantitatively converted to products 6'-O-acetylpuerarin (3a), 6'-O-decanoylpuerarin (3b), 6'-O-cinnamoylpuerarin (3c), respectively. The structures of these acylated products were determined by spectroscopic methods (MS and NMR).     

Biotransformation of podophyllotoxin by Hordeum vulgare cell suspension cultures

Hordeum vulgare cell suspension cultures were used to modify podophyllotoxin (1) One major product (1a) and one minor product (1b) were detected in both the culture medium and cells. To optimize the yield of compound 1a, we showed that: (1) the optimal concentration of added podophyllotoxin (1) was 33 mg L^-1; higher concentrations caused cell toxicity; (2) the stage of the cell cycle (lag/log/stationary) at which podophyllotoxin was added only marginally affected the yield of compound 1a; the optimal addition time was after lag phase, in which the yield of compound 1a reached ca. 76%, and (3) biotransformation of podophyllotoxin (1) was relatively slow; podophyllotoxin fed at 4 days after subculture resulted in yields of compound 1a of ca. 56, 64 and 76% after an additional 3, 6 and 10 days of incubation, respectively. Product 1a was purified and identified as isopicropodophyllone (1a) based on MS and NMR data.     

Biotransformation of γ-terpinene using Stemphylium botryosum (Wallroth) yields p-mentha-1,4-dien-9-ol, a novel odorous monoterpenol

A wild strain of Stemphylium botryosum, when grown submerged in the presence of γ-terpinene (1), yielded the novel highly odour active terpene alcohol (2), whose structure was established by spectroscopic means as p-mentha-1,4-dien-9-ol. During cultivation (2) was further oxidized, predominantly to the corresponding aromatic alcohol p-cymene-9-ol (5). The enantioselective enzymatic introduction of the hydroxyl group at the non-activated C9 of (1) resulted in an enantiomeric excess (ee) of 74% for (2) and 70% for (5), respectively.     

Book Review

LEGGETT, W. F. Ancient and Medieval Dyes. 5 × 8 in. 96 pp. Cloth. Chemical Publishing Co., Brooklyn, N. Y. 1944. $2.25.

Microtechnic In General. McCARTNEY, J. E. A new immersion oil “polyric”. J. Path. & Bact., 56, 265-6. 1944.

NICKERSON, MARK. A dry ice freezing unit for rotary microtomes. Science, 100, 177-8. 1944.

Dyes And Thedx Biological Uses. BERGEIM, FRANK H., and BRAKER, WILLIAM. Homosulfanilamides. J. Amer. Chem. Soc., 66, 1459. 1944.

CALDWELL, W. T., TYSON, F. T., and LAUER, LOTHAR. Substituted 2-sulfonamido-5-aminopyridines. II. J. Amer. Chem. Soc., 66, 1479. 1944.

JOHNS, C. K. Dye concentration in resazurin tablets. Amer. J. Pub. Health, 34, 955-8. 1944.

SMITH, WINSLOW WHITNEY. Relative sensitivity of different phases of growth curve of Bact. salmonicida to alkaline acriflavine. Proc. Soc. Exp. Biol. & Med., 56, 240-2. 1844.

VAN ARENDONK, A. M., and SHOULE, H. A. Dialkylaminoalkyl derivatives of substituted quinolines and quinaldines. J. Amer. Chem. Soc., 66, 1284. 1944.

WHEELER, KEITH, and DEGERING, E. F. Preparation and properties of certain derivatives of sulfamide. J. Amer. Chem. Soc., 66, 1242. 1944.

Animal Microtechnic. BOARDMAN, EDWARD T. Methods for collecting ticks for study and delineation. J. Parasitology, 30, 57-9. 1944.

DICKIE, MARGARET M. A new differential stain for mouse pituitary. Science, 100, 297-8. 1944.

GOVAN, A. D. TELFORD. Fat staining by Sudan dyes suspended in watery media. J. Path. & Bact., 56, 262-4. 1944.

LILLIE, R. D., and ASHBURN, L. L. Supersaturated solutions of fat stains in dilute isopropanol for demonstration of acute fatty degenerations not shown by Herxheimer technic. Arch. Path., 36, 432. 1943.

MULLEN, J. P. A convenient and rapid method for staining glycogen in paraffin sections with Best's carmine stain. Amer. J. Clin. Path., Tech. Sect., 8, 9-10. 1944.

NYKA, W. A method for staining the rickettsiae of typhns in histological sections. J. Path. & Bact., 56, 264. 1944.

POPPER, HANS, GYORGY, PAUL, and GOLDBLATT, H. Fluorescent material (ceroid) in experimental nutritional cirrhosis. Arch. Path., 37, 161. 1944.

SMALL, C. S., and SCHULTZ, M. A. Sustaining faded tissue sections. Amer. J. Clin. Path., Tech. Sect., 7, 66-7. 1943.

YOFFEY, J. M., and PARNELL, J. The lymphocyte content of rabbit bone marrow. J. Anat., 78, 109-12. 1944.

ZIEGLER, E. E. Hematoxylin-eosin tissue stain. An improved, rapid, and uniform technic. Arch. Path., 37, 68. 1044.

Plant Microtechnic. HAASIS, FERDINAND W. Staining rubber in ground or milled plant tissues. Ind. and Eng. Chem., Anal. Ed., 16, 480. 1944.

PARRIS, G. K. A simple nuclear stain and staining technique for Helminthosporia. Phytopathology, 34, 700. 1944.

Microorganisms. DARZINS, E. Rickettsienstudien. Zentbl. Bakl., Abt. I, Orig., 151, 18-20. 1943.

GOHAR, M. A. A staining method for Corynebacterium diphtheriae. J. Bact., 47, 575. 1944.

GRAY, P. H. H. Two-stain method for direct bacteria count. J. Milk Techn., 6, 76. 1943.     

CRISPR/Cas系统与志贺菌毒力和耐药的关系及插入序列IS600对cse2表达水平的影响北大核心CSCD

【目的】了解志贺菌中成簇的规律间隔短回文重复序列(Clustered regularly interspaced short palindromic repeats,CRISPR)的分布及其与毒力和耐药的关系,并分析志贺菌中插入序列IS600对CRISPR相关蛋白基因cse2 m RNA表达水平的影响。【方法】利用课题组前期设计的引物PCR扩增志贺菌的3个CRISPR位点、CRISPR相关蛋白基因cse2、耐药基因和毒力基因;改良Kirby-Bauer(K-B)纸片法进行药敏试验;台盼蓝计数试验检测细菌毒力;Real-time PCR检测志贺菌中cse2基因m RNA表达水平。分别分析志贺菌中CRISPR/Cas系统与耐药基因、耐药表型、毒力基因、毒力表型的关系;了解IS600对CRISPR相关蛋白基因cse2 m RNA表达水平的影响。【结果】志贺菌中CRISPR1位点阴性细菌的毒力强;插入序列IS600使cse2 m RNA表达水平降低。【结论】志贺菌中存在CRISPR1、2、3位点;CRISPR1位点与毒力有关;插入序列IS600对cse2 m RNA表达水平有影响。     

An Efficient Chemoenzymatic Synthesis of S-(-)-Fenpropimorph

First enantioselective synthesis of S-(-)-1-[3-(4-tert-butylphenyl)-2-methyl]propyl-cis-3,5-dimethylmorpholine (6), biologically active enantiomer of the systematic fungicide fenpropimorph, is reported. It comprises reacting 4-tert-butylbenzylbromide with methyldiethylmalonate, decarbethoxylation of 2 into racemic 3-(4-tert-butylphenyl)-2-methylpropionic acid ethylester (3) in DMSO in the presence of alkali, then Pseudomonas sp. lipase catalyzed kinetic resolution of racemic 3 into S-(+)-acid (4), base-catalyzed racemization and recycling of the R-(-)-ester 3, acylation of cis-3,5-dimethylmorpholine, and final reduction of the intermediary amide 5 to provide enantiomerically pure S-(-)-6.     

Studies on composition and stability of a large membered bacterial consortium degrading phenol

A ten member microbial consortium (AS) consisting of eight phenol-degrading and two non-phenol-degrading strains of bacteria was developed and maintained in a fed-batch reactor by feeding 500 mg l⁻¹ phenol for four years at 28 ± 3 °C. The consortium could degrade 99% of 500 mg l⁻¹ phenol after 24 hours incubation with a biomass increase of 2.6 × 10⁷ to 4 × 10¹² CFU ml⁻¹. Characterization of the members revealed that it consisted of 4 principal genera, Bacillus, Pseudomonas, Rhodococcus, Streptomyces and an unidentified bacterium. Phenol degradation by the mixed culture and Bacillus subtilis, an isolate from the consortium was compared using a range of phenol concentrations (400 to 700 mg l⁻¹) and by mixing with either 160 mg l⁻¹ glucose or 50 mg l⁻¹ of 2,4-dichlorophenol in the medium. Simultaneous utilization of unrelated mixed substrates (glucose/2,4-dichlorophenol) by the consortium and Bacillus subtilis, indicated the diauxic growth pattern of the organisms. A unique characteristic of the members of the consortia was their ability to oxidize chloro aromatic compounds via meta pathway and methyl aromatic compounds via ortho cleavage pathway. The ability of a large membered microbial consortia to maintain its stability with respect to its composition and effectiveness in phenol degradation indicated its suitability for bioremediation applications.     

微生物降解秸秆木质素的研究进展

我国秸秆资源丰富，每年产生逾8亿t作物秸秆。通过秸秆直接还田或肥料化还田不仅可以减少化肥的施用量，缓解农业污染压力，还能实现农作物秸秆的循环利用。木质素结构复杂，且与纤维素和半纤维素相互缠绕，因此秸秆的自然腐解过程中，木质素是主要的限速因子，为了提高降解效率，木质素降解菌的发掘和降解机制也逐渐成为研究热点。本文综述了降解木质素的真菌和细菌的研究现状，对比其真菌和细菌降解特性的优缺点并分析复合降解菌群的优势。随后对木质素降解酶系的酶学性质、在不同微生物中的表达特性进行总结，对木质素降解机制及衍生芳烃代谢路径的研究进展进行综述。最后整理木质素降解微生物在秸秆肥料化技术中的应用进展，并探讨了微生物降解秸秆木质素的应用前景和未来的研究方向。