Degradation and Utilization of Hemicellulose from Intact Forages by Pure Cultures of Rumen Bacteria

Several pure strains of rumen bacteria have previously been shown to degrade isolated hemicelluloses from a form insoluble in 80% acidified ethanol to a soluble form, regardless of the eventual ability of the organism to utilize the end products as energy sources. This study was undertaken to determine whether similar hemicellulose degradation or utilization, or both, occurs from intact forages. Fermentations by pure cultures were run to completion by using three maturity stages of alfalfa and two maturity stages of bromegrass as individual substrates. Organisms capable of utilizing xylan or isolated hemicelluloses could degrade and utilize intact forage hemicellulose, with the exception of two strains of Bacteroides ruminicola which were unable to degrade or utilize hemicellulose from grass hays. Intact forage hemicelluloses were extensively degraded by three cellulolytic strains that were unable to use the end products; in general, these strains degraded a considerably greater amount of hemicelluloses than the hemicellulolytic organisms. Hemicellulose degradation or utilization, or both, varied markedly with the different species and strains of bacteria, as well as with the type and maturity stage of the forage. Definite synergism was observed when a degrading nonutilizer was combined with either one of two hemicellulolytic strains on the bromegrass substrates. One hemicellulolytic strain, which could not degrade or utilize any of the intact bromegrass hemicellulose alone, almost completely utilized the end products solubilized by the nonutilizer. Similar synergism, although of lesser magnitude, was observed when alfalfa was used as a substrate.     

THE EFFECT OF ADDED NITROGEN ON THE RATE OF DECOMPOSITION OF ORGANIC MATTER

(1) N added to decomposing organic matter often has no effect or a negative effect on microbial activity, at least in the long term. More than 60 papers are cited in support of this statement.
(2) The negative effect of N is mainly found with recalcitrant organic matter with a high C/N ratio (straw, wood, etc.), whereas a positive effect of N is common for easily degradable organic material with low C/N ratio.
(3) The negative effect of N could be explained by: (i) N disturbs the outcome of competition between potent and less potent decomposers; (ii) through 'ammonia metabolite repression', N blocks production of certain enzymes, at least in basidiomycetes, and enhances breakdown of the most available cellulose, whereby recalcitrant lignocellulose accumulates; (iii) amino compounds condense with polyphenols and other decomposition products, forming 'browning precursors' which are toxic or inhibitory.
(4) The effect of adding N may depend on the microflora present.
(5) There are indications that some microorganisms have a 'luxury uptake' of N when it is present in sufficient amounts, thereby delaying N mineralization.
(6) The addition of N seems to increase the formation of water-soluble , brown, recalcitrant compounds, but to decrease the amount of humus formed.     

Organic matter availability structures microbial biomass and activity in a Mediterranean stream

1. We compared microbial biomass (bacteria, fungi, algae) and the activity of extracellular enzymes used in the decomposition of organic matter (OM) among different benthic substrata (leaves, coarse and fine substrata) over one hydrological year in a Mediterranean stream.
2. Microbial heterotrophic biomass (bacteria plus fungi) was generally higher than autotrophic biomass (algae), except during short periods of high light availability in the spring and winter. During these periods, sources of OM shifted towards autochthonous sources derived mainly from algae, which was demonstrated by high algal biomass and peptidase activity in benthic communities.
3. Heterotrophic activity peaked in the autumn. Bacterial and fungal biomass increased with the decomposition of cellulose and hemicellulose compounds from leaf material. Later, lignin decomposition was stimulated in fine (sand, gravel) and coarse (rocks, boulders and cobbles) substrata by the accumulation of fine detritus.
4. The Mediterranean summer drought provoked an earlier leaf fall. The resumption of the water flow caused the weathering of riparian soils and subsequently a large increase in dissolved organic carbon and nitrate, which led to growth of bacteria and fungi.     

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。     

Microbial growth and detritus transformations during decomposition of leaf litter in a stream

SUMMARY. 1. Despite the widely accepted importance of bacteria and fungi in degrading detritus in aquatic ecosystems there is still very little quantitative information on the abundance and dynamics of these microorganisms. Using epifluorescent microscopy, we measured the biomass of bacteria and fungi during decomposition of three types of leaf detritus. Bacterial production was determined from the rate of incorporation of ³H-thymidine into DNA.
2. The transformation of leaf carbon into dissolved organic carbon and fine particulate organic carbon was followed in order to compare the amounts of leaf material that were converted into these 'end-products' of decomposition versus the amount converted into microbial biomass.
3. The amount of microbial carbon in the leaf-detritus complex never exceeded 5.2% of the total carbon, and fungal biomass was always much greater than bacterial biomass. Despite the greater standing stock of fungi, the rapid turnover of bacteria (doubling about once per day) implies that their role in degrading leaf litter or as a food source for detritivores might be as great as for fungi.
4. Removal of microbial biomass from leaf litter may occur as release of fungal spores and consumption or shedding of bacterial biomass. Fungal spores can be a significant part of the fine particulate organic carbon released from leaf detritus and potentially represent an important food resource for filter-feeding organisms.     

肺切除术患者下呼吸道细菌L型培养及其临床研究

本文在５０例行肺切除术中,分别采集病肺、支气管切缘、健侧支气管内分泌物４５０份,做常规细菌和细菌Ｌ型培养及药敏试验。分离出需氧菌和真菌６０株,厌氧菌１２株、细菌Ｌ型４２株。菌群主要分布在病肺内约占５０％。需氧菌种中Ｇ＋球菌占６１．７％,葡萄球菌多见;其次Ｇ￣＋杆菌占２３．３％,以肠杆菌科细菌为主。厌氧菌占细菌型１６．７％。细菌Ｌ型特点与细菌型一致。围术期选择作用于细胞壁和细胞质的抗生素,以杀灭细菌型及细菌Ｌ型感染。     

Succession and activity of microorganisms in stored bagasse

Summary Fresh sugarcane bagasse was fermented under defined conditions and investigated regarding a microbial succession during fermentation, in view of the enzyme activities of microorganisms against the main bagasse components: sucrose, pectin, hemicellulose, cellulose, and lignin.Altogether, 400 pure cultures of microorganisms were obtained from 8 g bagasse during 6.5 days of storage. This flora consists of bacteria (74%), actinomycetes (6%), yeasts (13%), and fungi (7%). The yeasts dominate in early fermentation, followed by bacteria, and then by actinomycetes and fungi.This succession coincides with the enzymic activities of the isolated organisms during fermentation. At first, residual sugar is consumed predominantly by the yeasts. Then the bacteria degrade the pectin, the hemicellulose, and in parts, the cellulose. Later, the actinomycetes and the fungi imperfecti attack the hemicellulose, the cellulose, and, partly, the lignin within the bagasse fiber.These results are corroborated by investigations using bagasse from bulk storage.     

Radiation and fermentation treatment of cellulosic wastes

The effect of radiation pasteurization of sugar cane bagasse and rice straw and fermentation using various strains of fungi were studied for upgrading of cellulosic wastes. The initial contamination by fungi and aerobic bacteria both in bagasse and straw was high. The doses of 30 kGy for sterilization and 8 kGy for elimination of fungi were required. Irradiation effect showed that rice straw contained comparatively radioresistant microorganisms. It was observed that all the fungi (Hericium erinacium, Pleurotus djamor, Ganoderma lucidum, Auricularia auricula, Lentinus sajor-caju, Coriolus versicolor, Polyporus arcularius, Coprinus cinereus) grow extending over the entire substrates during one month after inoculation in irradiated bagasse and rice straw with 3% rice bran and 65% moisture content incubated at 30°C. Initially, sugar cane bagasse and rice straw substrates contained 39.4% and 25.9% of cellulose, 22.9% and 26.9% of hemicellulose, and 19.6% and 13.9% of lignin + cutin, respectively. Neutral detergent fibre (NDF) values decreased significantly in sugar cane bagasse fermented byG. lucidum, A. auricula andP. arcularius, and in rice straw fermented by all the 8 strains of fungi. Acid detergent fibre (ADF) values also decreased in bagasse and rice straw fermented by all the fungi.P. arcularius, H. erinacium, G. lucidum andC. cinereus were found to be the most effective strains for delignification of sugar cane bagasse.     

Biological N2 fixation by heterotrophic and phototrophic bacteria in association with straw

Much of the crop residues, including cereal straw, that are produced worldwide are lost by burning. Plant residues, and in particular straw, contain large amounts of carbon (cellulose and hemicellulose) which can serve as substrates for the production of microbial biomass and for biological N₂ fixation by a range of free-living, diazotrophic bacteria. Microorganisms with the dual ability to utilise cellulose and fix N₂ are rate, but some strains that utilize hemicellulose and fix N₂ have been found. Generally, cellulolysis and diazotrophy are carried out by a mixed microbial community in which N₂-fixing bacteria utilise cellobiose and glucose produced from straw by cellulolytic microorganisms. N₂-fixing bacteria include heterotrophic and phototrophic organisms and the latter are apparently more prominent in flooded soils such as rice paddies than in dryland soils. The relative contributions of N₂ fixed by heterotrophic diazotrophic bacteria compared with cyanobacteria and other phototrophic bacteria depend on the availability of substrates from straw decomposition and on environmental pressures. Measurements of asymbiotic N₂ fixation are limited and variable but, in rice paddy systems, rates of 25 kg N ha^-1 over 30 days have been found, whereas in dryland systems with wheat straw, in situ measurements have indicated up to 12 kg N ha^-1 over 22 days. Straw-associated N₂ fixation is directly affected by environmental factors such as temperature, moisture, oxygen concentration, soil pH and clay content as well as farm management practices. Modification of managements and use of inoculants offer ways of improving asymbiotic N₂ fixation.In laboratory culture systems, inoculation of straws with cellulolytic and diazotrophic microorganisms has resulted in significant increases in N₂ fixation in comparison to uninoculated controls and gains of N of up to 72 mg N fixed g^-1 straw consumed have been obtained, indicating the potential of inoculation to improve N gains in composts that can then be used as biofertilisers. Soils, on the other hand, contain established, indigenous microbial populations which tend to exclude inoculant microorganisms by competition. As a consequence, improvements in straw-associated N₂ fixation in soils have been achieved mostly by specific straw-management practices which encourage microbial activity by straw-decomposing and N₂-fixing microorganisms.Further research is needed to quantify more accurately the contribution of asymbiotic N₂ fixation to cropping systems. New strains of inoculants, including those capable of both cellulolytic and N₂-fixing activity, are needed to improve the N content of biofertilisers produced from composts. Developments of management practices in farming systems may result in further improvements in N₂ fixation in the field.     

THE CONTROL OF DISEASES OF LETTUCE BY THE USE OF ANTAGONISTIC ORGANISMS I. THE CONTROL OF BOTRYTIS CINEREA PERS.

The antagonism of a number of bacteria, actinomycetes and fungi to Botrytis cinerea in pure culture on lettuce extract agar has been investigated. A considerable number were antagonistic at 25° C., a few showed antagonism at 15° C. and a limited number grew and were active at 5° C.
Certain of these organisms were able to control rot of detached lettuce leaves when inoculated before or simultaneously with B. cinerea. The latter is unable to penetrate areas of dead tissue colonized by selected antagonists.
Control of rot was also obtained when leaves of growing plants were similarly inoculated.
Substantial control of disease occurred when young potted plants in frames were sprayed with suspensions of selected antagonists in 1.0 % glucose solution.
The practicability of this method of control is discussed.     

九龙江口秋茄（Kandelia candel）红树林掉落叶自然分解与落叶腐解微生物的关系

 通过对九龙江口秋茄红树林人工模拟凋落叶自然分解过程中落叶腐解与落叶腐解微生物变化的研究,结果表明：1．随落叶分解进程,落叶腐解微生物数量有了显著地变化;就细菌、放线菌和丝状真菌等三大类群微生物数量来看,整个过程以细菌占绝对优势,其数量在200×104一8800×104个／克干重,占三大类群微生物总数量的96—99%以上。这表明细菌是落叶分解起主要作用的微生物类群。2．微生物各生理类群中,以氨化细菌数量最多,在26×104一180×104个／克干重;而亚硝化细菌,反硝化细菌及纤维分解菌分别仅在0.03×104一0.24×104,0.03×104一0.10×104及1.14×104一7.33×104个／克干重。表明氨化细菌是有机物质无机化的主要生理类群。并且氨化作用、亚硝化作用和反硝化作用是同时进行;并随落叶腐解周期的延长(半腐解周期内)而加强,唯强度不一,它反映了该生境干、湿交替的沼泽化特点。纤维分解菌数量的变化较特殊,在落叶腐解第2周时,有了明显增多,至第4周达全周期的最高值,而以后周期都与初始叶面纤维分解菌的数量相近,甚至减少。从微生物活性的变化测定结果来看,与上述微生物生理类群的变化特点是相一致的。3．在该生境中,落叶腐解速度是很快的,当落叶入土1周后将近1／4有机物被腐解,至第6周达半腐解状态。随落叶腐解有机物质无机化程度的加速,残叶中单位叶重的可溶性总糖含量和全磷量都明显地减少,而全氮含量显著地增加。     

DECOMPOSITION IN ESTUARINE ECOSYSTEMS

SUMMARY

The varied sources of estuarine plant detritus and the processes and organisms involved in its decomposition are discussed in this review. In the case of emergent and peripheral vegetation, microbial decomposition commences in the phylloplane, with fairly rapid leaching of DOM occurring soon after immersion. Residual POM, largely cellulose, is decomposed more slowly by cellulolytic micro-organisms. Phytoplankton start contributing to the DOM pool before senescence by excreting soluble substances during normal metabolism and interesting regulatory mechanisms are Involved in the bacterial utilization of this material. Bacteria play a more important role than fungi in decomposition and the latter appear to be prominent only in the breakdown of mangrove litter. Predaceous microflagellates and other protists occur in association with the bacteria and feed on them, enhancing decomposition by maintaining optimal bacterial growth rates. They appear to play a more important role in mineralization than do the bacteria, which are more effective in the conservation of nutrients upon which their efficiency of detritus incorporation Is dependent. Aerobic decomposition tends to terminate in complete mineralization, whereas under anaerobic conditions incomplete oxidation yields organic end products such as volatile fatty acids. A comparison of this process with the functioning of the herbivore rumen leads to the conclusion that the latter is more cost-effective in energy terms. Contrary to earlier published statements that estuaries are major exporters of energy in the form of detritus, many export very little of this material, or are net importers. Finally, the methods for studying decomposition in estuaries must be carefully chosen because of the environmental diversity of these systems. This is particularly true of radio-labelled substrates used for uptake and turnover studies; there appears to be no universal substrate or approach.     

Fermentation of barley straw by anaerobic rumen bacteria and fungi in axenic culture and in co-culture with methanogens

When incubated in axenic culture, strains of anaerobic rumen fungi were more active than cellulolytic bacteria in solubilizing barley straw stem fragments 5 to 10 mm in length. Pretreatment with ammonia had little effect on microbial attack. Of three species of methanogens tested, Methanobrevibacter smithii strain PS formed the most stable and reproducible co-cultures with the fungi and with Ruminococcus albus , and the presence of this organism enhanced the extent of degradation of straw, although this effect was less marked than that previously observed when pure cellulose was used as substrate.     

纤维素分解菌对不同纤维素类物质的分解作用

经过CMC平板、滤纸液化和摇瓶培养试验 ,发现 6株菌中 ,产黄纤维单胞菌 (CellulomonasFlav igena)和康氏木霉 (Trichodermakonigii)分解纤维素类物质的能力比较强 ,对来源不同的纤维素类物质分解能力差异很大 ;真菌与细菌一起接种时 ,分解纤维素类物质的速度明显高于其中任何一个单一菌株 ,说明纤维素类物质的分解需要多种微生物的联合作用     

The key role of lignin decomposing fungi in the decay of roofs thatched with water reed

We investigated the involvement of microorganisms in the rapid reed decay of roofs thatched with water reed. Numerous bacteria and fungi were isolated by enrichment cultures from reed samples and from fungal fruit bodies on roofs. All strains were characterised in respect to their abilities to degrade cellulose, hemicelluloses and the lignin model substance Poly-R-478. Only 15 of the 92 isolated bacterial strains were capable of degrading cellulose and hemicelluloses. However, nearly all 61 of the identified fungal isolates had these abilities. Nevertheless, only 14 of the isolated fungal strains as well as a reference isolate of Trametes versicolor were capable of degrading Poly-R-478. The ability of the microorganisms to attack complete reed was assessed using a newly developed test system which measures the loss of dry weight during the incubation. A significant loss of dry weight was apparent only in tests using the ligninolytic fungi Pycnoporus cinnabarinus, Trametes versicolor, Phlebia tremellosa and some Mycena species, but not in the case of the majority of cellulolytic bacteria and fungi. From these results, we conclude that ligninolytic fungi are capable of destroying complete reed structure and that they play the key role in the process of the rapid decay of roofs thatched with reed. Directly after the initial lignin attack, cellulose and hemicellulose were degraded to a great extent, evidenced by the large loss of dry weight (up to 72 %), which significantly exceeds the lignin content of reed (ca. 15 %). However, after the initial attack by ligninolytic fungi, bacteria or other fungi capable of degrading cellulose and hemicelluloses may contribute to the progressive decay of reed under natural conditions. Furthermore, we show that the rate of decay depends on the source of the reed and on the reed quality.     

Degradation of wheat straw by Fibrobacter succinogenes S85: a liquid- and solid-state nuclear magnetic resonance study

Wheat straw degradation by Fibrobacter succinogenes was monitored by nuclear magnetic resonance (NMR) spectroscopy and chemolytic methods to investigate the activity of an entire fibrolytic system on an intact complex substrate. In situ solid-state NMR with 13C cross-polarization magic angle spinning was used to monitor the modification of the composition and structure of lignocellulosic fibers (of 13C-enriched wheat straw) during the growth of bacteria on this substrate. There was no preferential degradation either of amorphous regions of cellulose versus crystalline regions or of cellulose versus hemicelluloses in wheat straw. This suggests either a simultaneous degradation of the amorphous and crystalline parts of cellulose and of cellulose and hemicelluloses by the enzymes or degradation at the surface at a molecular scale that cannot be detected by NMR. Liquid-state two-dimensional NMR experiments and chemolytic methods were used to analyze in detail the various sugars released into the culture medium. An integration of NMR signals enabled the quantification of oligosaccharides produced from wheat straw at various times of culture and showed the sequential activities of some of the fibrolytic enzymes of F. succinogenes S85 on wheat straw. In particular, acetylxylan esterase appeared to be more active than arabinofuranosidase, which was more active than alpha-glucuronidase. Finally, cellodextrins did not accumulate to a great extent in the culture medium.     

Effect of alkaline and autohydrolysis processes on the purity of obtained hemicelluloses from corn stalks

A study of the potential of autohydrolysis and alkaline extraction processes from corn stalks was performed for high purity hemicellulose extraction. The influence of process parameters on the purity of obtained hemicelluloses was analyzed. An experimental design was developed for the autohydrolysis treatments to determine the optimal conditions to solubilize the hemicelluloses with lowest content in contaminants. On the other hand, alkaline extraction, including raw material pretreatment (dewaxing and delignification step) was carried out analyzing the effectiveness of this processes for maximum pure hemicellulose recovery. The maximum yield (54% of the raw material hemicelluloses) and the best physicochemical properties (highest hemicellulose content free of lignin) were obtained with these pretreatments in alkaline extraction. Moreover, the effect of lignin removal by sulfuric acid from the autohydrolysis liquors before hemicellulose precipitation was studied. This purification step has allowed to obtain lignin-free autohydrolysis hemicellulose but with the presence of sulfur as predominant contaminant.     

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。     

Screening microbial strain for improving the nutritional value of wheat and corn straws as animal feed

From 18 strains of cellulolytic microorganisms including bacteria and filamentous fungi, one strain of soft rot fungus identified as Chaetomium cellulolyticum was screened with respect to stronger decomposition ability of cellulose and hemicellulose and its ability for protein synthesis. As it grew on raw corn straw in solid layer fermentation (SLF) for 5 days, the amino acid content in the fermentation product attained 19.29% (w/w) from 6.43% while the total cell wall was reduced by 54%. A toxicity test with mice showed that the fermentation product is not poisonous. The two filamentous fungi, Trichoderma pseudokoningii S-38 and Penicillium decumbens JU-A10 produced large amounts of extracellular cellulase and hemicellulase in the SLF process, but their growth was limited and they sporulated profusely with regard to their value as animal feed products.     

小麦根区微生物分解小麦残体产生的化感物质及其生物活性的研究

取小麦根区土壤微生物于不同ｐＨ（５,７,８）条件下,在室内腐解成熟期麦秸。对不同时间提取物做生物活性检验,部分样品进行ＧＣ－ＭＳ测定。结果表明：酸性提取液对小麦,玉米种子萌发均表现出抑制作用,其强弱与腐解时间有关。第１天的提取物对小麦、玉米根长的抑制作用极显著（Ｐ〈０．０１）,第２周的提取物,以ｐＨ７时对小麦抑制最强,萌发率为零。第４周提取物ｐＨ８（Ａ）对小麦不但无抑制作用,反而有明显的刺激作用。