不同粮仓中稻谷优势霉菌的鉴定及差异性分析

为了研究稻谷中优势霉菌的种类、数量以及变化趋势,本试验以湖南省3个不同地区稻谷为研究对象,通过初步判断各粮仓优势霉菌,结合分子生物学方法对其ITS 序列进行分析,并对稻谷霉菌进行带菌量测定。结果表明,3个粮仓中,金牛仓稻谷中优势菌株分别为根霉、米曲霉、毛霉、黑曲霉、烟曲霉、黄曲霉、白曲霉、桔青霉;金山仓稻谷中优势菌株分别为根霉、米曲霉、毛霉、黑曲霉、黄曲霉、白曲霉、桔青霉;银光仓稻谷中优势菌株分别为根霉、米曲霉、毛霉、黑曲霉、黄曲霉。3个粮仓中根霉数量分布均表现为上层>下层>中层,米曲霉为中层>上层>下层,毛霉、黑曲霉、黄曲霉的分布为上层>中层>下层,同一霉菌在同一粮仓不同粮层间数量存在显著差异(P<0.05);随着储藏时间的延长,米曲霉、黑曲霉、黄曲霉数量逐渐减少,根霉、毛霉数量增加,同一霉菌在不同储藏时间霉菌数量存在差异显著(P<0.05)。本研究结果为稻谷安全储藏与霉菌防控提供了一定的理论依据。     

Structure-antifungal activity relationship of cinnamic acid derivatives

A structure-antifungal activity relationship (SAR) study of 22 related cinnamic acid derivatives was carried out. Attention was focused on the antifungal activities exhibited against Aspergillus flavus, Aspergillus terreus, and Aspergillus niger. (E)-3-(4-methoxy-3-(3-methylbut-2-enyl)phenyl)acrylic acid (16) exhibited antifungal activity against A. niger, comparable to that of miconazole and a significant antifungal effect against A. flavus and A. terreus as well. A structure-activity relationship (SAR) study of related cinnamic acid derivatives has allowed a model to be proposed for the recognition of the minimal structural requirements for the antifungal effect in this series.     

黑曲霉发酵滤液杀食用菌线虫活性初探

对灭菌的黑曲霉发酵滤液杀线虫作用进行了研究,找到经济有效的发酵滤液培养基为豆芽汁培养基。不同浓度、不同pH值的发酵滤液均能影响其杀线效果。pH为3．0的发酵滤液原液,杀线作用及抑制线虫虫卵孵化均达100％;当pH调为5．0时,杀线校正死亡率仍达73．90％;pH5．5时,杀线校正死亡率下降到8．15％。发酵滤液原液稀释到4倍液时,杀线校正死亡率仍达60．47％;稀释6倍液时下降至25．92％。在蘑菇栽培的防治线虫试验中,蘑菇栽培料添加发酵滤液后能减少线虫的数量,同时还具有促进菌丝生长的作用;仅加发酵滤液处理比未加发酵滤液及线虫处理的生物转化率提高76．30％,加发酵滤液及线虫处理比仅加线虫处理的则提高81．41％。     

Inhibitory effects of gossypol, gossypolone, and apogossypolone on a collection of economically important filamentous fungi

Racemic gossypol and its related derivatives gossypolone and apogossypolone demonstrated significant growth inhibition against a diverse collection of filamentous fungi that included Aspergillus flavus, Aspergillus parasiticus, Aspergillus alliaceus, Aspergillus fumigatus, Fusarium graminearum, Fusarium moniliforme, Penicillium chrysogenum, Penicillium corylophilum, and Stachybotrys atra. The compounds were tested in a Czapek agar medium at a concentration of 100 μg/mL. Racemic gossypol and apogossypolone inhibited growth by up to 95%, whereas gossypolone effected 100% growth inhibition in all fungal isolates tested except A. flavus. Growth inhibition was variable during the observed time period for all tested fungi capable of growth in these treatment conditions. Gossypolone demonstrated significant aflatoxin biosynthesis inhibition in A. flavus AF13 (B(1), 76% inhibition). Apogossypolone was the most potent aflatoxin inhibitor, showing greater than 90% inhibition against A. flavus and greater than 65% inhibition against A. parasiticus (B(1), 67%; G(1), 68%). Gossypol was an ineffectual inhibitor of aflatoxin biosynthesis in both A. flavus and A. parasiticus. Both gossypol and apogossypolone demonstrated significant inhibition of ochratoxin A production (47%; 91%, respectively) in cultures of A. alliaceus.     

Susceptibility of Pythium spp and other fungi to antagonism by the mycorparasite Phytium Oligandrum

Phytium spp and isolates within species differed in susceptibility to the mycoparasite Pythium oligandrum Drechs., as evidenced by their degree of inhibition by it on cellulose and ability to support its growth across their colonies on agar. Yet no Phythium sp. was highly susceptible to it, and P. graminicola Subramanian was highly resistant.No evidence was found that P. oligandrum produces toxins active against other fungi. In liquid culture, P. oligandrum grew on undisturbed colonies of Phialophora sp. (highly susceptible) but not P. ultimum Trow or Fusarium culmorum (W. G. Sm.) Sacc. (moderately resistant) and not Rhizoctonia solani Kuhn (highly resistant). It grew in culture filtrates of Phialophora sp., P. ultimum and F. culmorum, utilizing organic nitrogen and thiamine released by these fungi, but not in culture filtrates of R. solani. It grew on mycelial macerates of all these fungi, though poorly on those of R. solani. Resistance to parasitism by P. oligandrum seems to reside, at least partly, in low levels of nutrient release from host hyphae.     

Antifungal properties of wheat histones (H1-H4) and purified wheat histone H1

Wheat ( Triticum spp.) histones H1, H2, H3, and H4 were extracted, and H1 was further purified. The effect of these histones on specific fungi that may or may not be pathogenic to wheat was determined. These fungi included Aspergillus flavus , Aspergillus fumigatus , Aspergillus niger , Fusarium oxysporum , Fusarium verticillioides , Fusarium solani , Fusarium graminearum , Penicillium digitatum , Penicillium italicum , and Greeneria uvicola . Non-germinated and germinating conidia of these fungi were bioassayed separately. The non-germinated and germinating conidia of all Fusarium species were highly susceptible to the mixture (H1-H4) as well as pure H1, with viability losses of 99-100% found to be significant (p < 0.001) at ≤10 μM or less for the histone mixture and pure H1. F. graminearum was the most sensitive to histone activity. The histones were inactive against all of the non-germinated Penicillium spp. conidia. However, they significantly reduced the viability of the germinating conidia of the Penicillium spp. conidia, with 95% loss at 2.5 μM. Non-germinated and germinating conidia viability of the Aspergillus spp. and G. uvicola were unaffected when exposed to histones up to 10 μM. Results indicate that Fusarium spp. pathogenic to wheat are susceptible to wheat histones, indicating that these proteins may be a resistance mechanism in wheat against fungal infection.     

Effect of SO2 and NH3 on growth behavior of some phylloplane fungi of wheat in in vitro

The colony growth of some phylloplane fungi of wheat viz. Alternaria alternata, Aspergillus favus, Amiger, Cladosportium cladosporioides, Curvularia lunata, Drechslera australiensis, Epicoccum purpurascens, Fusarium oxysporum, Penicillium chrysogenum and P. citrinum were studied in chamber fumigation experiments exposed to 2669 ± 105 μg SO₂ m^?3 and 708.33 ± 55 μg NH3 m^?3 air, separately, for 10, 30 and 60 min. The colony growth of all the test fungi was significantly (P=0.01/0.005) inhibited on prolonged period of SO₂/NH₃ exposure. However, some of the test fungi namely A. favus, A. niger, E. purpurascens and F. oxysporum showed growth stimulation after 10 min exposure of SO₂. Similarly, the growth of C. lunata and F. oxysporum increased only after 10 min exposure of NH3. The inhibitory effect of SO₂/NH₃ was directly correlated with the exposure times.     

Corncob-induced endo-1,4-beta-d-xylanase of Aspergillus oryzae MTCC 5154: production and characterization of xylobiose from glucuronoxylan

Eight different fungi were cultivated in a peptone-yeast extract medium containing 1% oat spelt xylan (OSX) to evaluate endo-1,4-beta-xylanase secretion for xylooligosaccharide (XOS) production. Aspergillus oryzae MTCC 5154, Aspergillus flavus , Aspergillus niger , and Aspergillus ochraceus showed significant titers of endoxylanases, which were further used for the production of XOS from birch wood xylan (BWX). A. oryzae produced 89.5 +/- 1.13% XOS in the hydrolysate at 24 h of reaction. The effect of OSX, BWX, and raw corncob on the induction of endoxylanase in A. oryzae was studied, and the xylanase activity was maximum at 96 h of cultivation in 3% corncob containing medium. XOS produced at 36 h of reaction was 5.87 +/- 0.53 mg/mL (12 +/- 2% xylose, 48 +/- 2.43% xylobiose, and 40 +/- 3.6% higher oligomers) from 1% BWX . HPLC/refractive index detection and ESI/MS analysis of fractions obtained by GPC corresponded to neutral and 4- O-methyl-alpha- d-glucuronic acid substituted acidic oligosaccharides. The major fraction, beta- d-xylopyranosyl-(1-->4)- d-xylanopyranose was characterized using (13)C NMR.     

七种培养基对黄曲霉分离效果的比较

为了筛选出适宜黄曲霉分离的培养基,比较了7种常用于霉菌分离的培养基对10个花生土壤样品的黄曲霉分离效果,这7种培养基为氯硝胺18%甘油培养基(DG18)、高盐察氏培养基(SCDA)、马铃薯琼脂培养基(PDA)、改良的孟加拉红培养基(M-RB)、YES培养基、孟加拉红培养基(RB)、氯硝胺孟加拉红琼脂(DRBC)。研究发现7种培养基对黄曲霉菌培养效果差别很大,培养效果最好的是DG18,黄曲霉的培养数是PDA的7.3倍。同时DG18能很好的抑制毛霉的生长,与DRBC培养基相比,能抑制81%的毛霉菌生长。因此DG18培养基能最大限度的保证黄曲霉的生长分离,同时也能更好地抑制毛霉的生长,更适用于黄曲霉种群、遗传方面的研究应用。     

Biovolatilization of Arsenic by Different Fungal Strains

The quantification of arsenic biovolatilization by microscopic filamentous fungi Aspergillus clavatus, A. niger, Trichoderma viride and Penicillium glabrum under laboratory conditions is discussed in this article. The fungi were cultivated on a liquid medium enriched with inorganic arsenic in pentavalent form (H₃AsO₄). Filamentous fungi volatilized 0.010 mg to 0.067 mg and 0.093 mg to 0.262 mg of arsenic from cultivation systems enriched with 0.25 mg (5 mg.l^?1 of arsenic in culture media) and 1.00 mg of arsenic (20 mg.l^?1 of arsenic in culture media), respectively. These results represent the loss of arsenic after a 30-day cultivation from cultivation systems. The production of volatile arsenic derivatives by the A. niger and A. clavatus strains was also determined by hourly sorption using the sorbent Anasorb (CSC) on the 29th day of cultivation.     

Fungal Generation of Organic Acids for Removal of Lead from Contaminated Soil

The use of solid-state fermentation (SFF) of low cost substrates by fungal species to generate organic acid solutions for washing of lead from a contaminated soil was evaluated in this study. SFF filtrates were generated by fermentation of four substrates (corn cobs, apple pomace, rice and hay) with three fungal species (Aspergillus niger NRRL 2001 (A. niger 1), Aspergillus niger ATCC 64065 (A. niger 2), Aspergillus foetidus NRRL 337) at three fermentation times. The concentration and speciation of organic acids of the filtrates was found to be a function of the substrate type, the fungal species and the fermentation time. Fermentation of rice resulted in the highest concentrations of citric acid while fermentation of corn cobs, apple pomace and hay tended to generate oxalic acid with an increasing fraction of this acid as the fermentation progressed. Batch extraction tests that employed the SSF filtrates revealed that soluble lead concentrations as high as 35 mg/l could be achieved. Filtrates containing elevated concentrations of citric acid resulted in the greatest lead extraction while oxalic acid inhibited solubilization. Due to the buffering of pH that was provided by the soil in the batch tests this factor did not appear to influence lead extraction. Lead extraction was observed over an extended period of time in a column test. Lead extraction was strongly influenced by the pH of the soil column and less strongly influenced by the organic acid content of the SSF filtrate. The speciation of organic acids was substantially modified from primarily citric acid in the SSF filtrate to gluconic acid in the soil column discharge.     

Occurrence of naphtho-gamma-pyrones- and ochratoxin A-producing fungi in French grapes and characterization of new naphtho-gamma-pyrone polyketide (aurasperone G) isolated from Aspergillus niger C-433

A survey on the occurrence on grape of fungi species in 2001 and their capability to produce ochratoxin A (OTA) and naphtho-gamma-pyrones (NGPs) was conducted in different vineyards from several French viticulture regions. The total numbers of fungal isolates, from setting to harvest, were 732. The Aspergillus genus was essentially represented by section Nigri (98.53%) and it was predominant (74.72%) when compared to Penicillium (25.27%). Approximately one third (30.46%) of the fungal isolates were OTA producers, and 94.17% belong to black aspergilli; Aspergillus carbonarius was the main OTA producer. Moreover, 8.33% of isolates (belong to A. carbonarius and A. niger) were NGP producers. However, none of the Penicillium spp. or other Aspergillus spp. isolates can produces NGP derivatives under the conditions used. No other study on NGPs production by fungi isolated from grapes has been reported. In the second part, a novel NGP, named aurasperone G (1), was isolated from the fermentation broth of the culture extracts of Aspergillus niger C-433, strain producer of OTA, along with the known compound aurasperone F (2). The chemical structure of the new polyketide was proposed based on complete (1)H and partial (13)C, COSY, HMQC, 1D NOE NMR spectra as well as UV and MS spectra. This new NGP was not reported before in nature or prepared synthetically.     

Competitive saprophytic colonization of pigeon-pea substrate by Fusarium udum in relation to environmental factors,chemical treatments and microbial antagonism

The competitive saprophytic colonization (CSC) of pigeon-pea substrates by Fusarium udum was studied in relation to environmental factors, chemical treatments and microbial antagonism. CSC was best at 22°C, good at 30°C, but at 40°C the substrate was vigorously colonized by Coprinus lagopus and Aspergillus nidulans which suppressed colonization by F. udum. High competitive saprophytic ability of F. udum was noted at pH 7 and 9 at soil moisture contents between 5 and 30%. At pH 4 and 5 F. udum was replaced by A. flavus and A. nidulans. The CSC of F. udum decreased in the soil-sand inoculum mixture amended with the fungicides bavistin, dithane Z-78 and difolatan. The herbicides 2,4-D and machete also reduced CSC by F. udum whereas urea promoted it. Colonization of pigeon-pea substrate by F. udum was highly suppressed by antagonism from Pénicillium citrinum, A. niger, Micromonospora gtobosa, A.flavus, A. terreus and Trichoderma viride when these were used in inoculum mixtures with F. udum or when substrates had already been colonized by them. Otherwise F. udum was shown to have a high competitive saprophytic ability.     

Fermentation of sugar beet waste by Aspergillus niger facilitates growth and P uptake of external mycelium of mixed populations of arbuscular mycorrhizal fungi

Sugar beet waste has potential value as a soil amendment and this work studied whether fermentation of the waste by Aspergillus niger would influence the growth and P uptake of arbuscular mycorrhizal (AM) fungi. Plants were grown in compartmentalised growth units, each with a root compartment (RC) and two lateral root-free compartments (RFC). One RFC contained untreated soil while the other RFC contained soil, which was uniformly mixed with sugar beet waste, either untreated (SB) or degraded by A. niger (ASB) in a rock phosphate (RP)-supplied medium. The soil in each pair of RFC was labelled with ³³P and ³²P in order to measure P uptake by the AM fungal mycelium, of which length density was also measured. Whole cell fatty acid (WCFA) signatures were used as biomarkers of the AM fungal mycelium and other soil microorganisms. The amount of biomarkers of saprotrophic fungi and both Gram-positive and Gram-negative bacteria was higher in SB than in ASB treatments. Whilst ASB increased growth and activity of AM mycelium, SB had the opposite effect. Moreover, shoot P content was increased by the addition of ASB, and by inoculation with AM fungi. Modification of soil microbial structure and production of exudates by A. niger, as a consequence of fermentation process of sugar beet waste, could possibly explain the increase of AM growth in ASB treatments. On the other hand, the highest P uptake was a result of the solubilisation of rock phosphate by A. niger during the fermentation.     

beta-glucosidases from five black Aspergillus species: study of their physico-chemical and biocatalytic properties

Five black Aspergillus strains (A. aculeatus, A. foetidus, A. japonicus, A. niger, and A. tubingensis) were cultivated on crude wheat arabinoxylan as the carbon source under defined pH, temperature, and oxygen conditions. Protein and beta-glucosidase content differed remarkably within the obtained culture filtrates, of which eleven beta-glucosidases were isolated. Seven beta-glucosidases were purified to apparent electrophoretic homogeneity using anion-exchange and gel-permeation chromatography. They were found to be acidic proteins and most of them appeared to be glycoproteins with a molecular mass between 93 and 142 kDa. Classification of the beta-glucosidases into four groups (I-A, I-B, II, and III) is suggested according to their physicochemical and biocatalytic properties. The major beta-glucosidases were assigned to groups I-A and I-B, the minor beta-glucosidases to groups II and III, comprising acid-tolerant and glucose-tolerant enzymes, respectively.     

Occurrence of ochratoxin A- and aflatoxin B1-producing fungi in Lebanese grapes and ochratoxin a content in musts and finished wines during 2004

This paper reports the results of an extensive survey on the occurrence of filamentous fungi isolated from wine-grapes in Lebanon and to test their ability to produce ochratoxin A (OTA) and aflatoxin B1 (AFB1) on CYA culture medium, in order to assess their potential for producing these mycotoxins on grapes. From the 470 grapes samples taken during season 2004, 550 fungi strains were isolated with 490 belonging to Aspergillus spp. and 60 belonging to Penicillium spp. All these isolated fungi starins were tested for their ability to produce OTA and AFB1. Aspergillus carbonarius shows that it is the only species able to produce OTA with a production percentage reaching 100% and a maximum concentration of 52.8 microg/g of Czapek yeast extract agar (CYA). In its turn, Aspergillus flavus was considered as the only AFB1-producing species with production percentage of 45.3% and a maximum concentration reaching 40 microg/g CYA. A total of 47 handmade musts produced from the collected grapes were also analyzed in order to correlate the presence of OTA in must and the occurrence of filamentous fungi on grapes; 57.4% were contaminated with OTA at low level with concentrations ranging between 0.011 and 0.221 microg OTA L(-1). The analysis of these must samples was not performed with regard to AFB1. Seventy samples of finish red wine were also assayed for OTA content. The results showed that 42 of the tested samples (60%) were found to be positive for OTA with low levels (0.012-0.126 microg OTA L(-1)).     

Comparative study of the effects of solid-state fermentation with three filamentous fungi on the total phenolics content (TPC), flavonoids, and antioxidant activities of subfractions from oats (Avena sativa L.)

The aim of present work was to investigate the effect of solid-state fermentation with filamentous fungi (Aspergillus oryzae var. effuses, Aspergillus oryzae, and Aspergillus niger) on total phenolics content (TPC), flavonoids, and antioxidant activities of four subfractions of oat, namely, n-hexane, ethyl acetate (EA), n-butanol, and water, and compare them to their corresponding subfractions of unfermented oat. The TPC and total flavonoids increased dramatically, especially in EA subfractions (p < 0.05). The levels of antioxidant activity of subfractions were also significantly enhanced (p < 0.05). The highest antioxidant activities were also found in the EA subfractions. The polyphenols in EA were analyzed by high-performance liquid chromatography at 280 nm. Most polyphenols were increased remarkably, especially ferulic and caffeic acids. There was a clear correlation between the TPC and antioxidant activity. In conclusion, fungi fermentation is a potential bioprocess for increasing the TPC, flavonoids, and antioxidant activities of oat-based food.     

Induction of the soybean phytoalexins coumestrol and glyceollin by Aspergillus

Several isoflavonoid phytoalexins produced by soybeans are known to be estrogenic, with potential beneficial health effects in humans. Increased production of phytoalexins by the soybean plant will facilitate research efforts in this area. In this study, phytoalexin induction and accumulation in soybean cotyledon tissue was observed using four species of Aspergillus: A. sojae, A. oryzae, A. niger, and A. flavus. All four Aspergillus species tested elicited phytoalexin accumulation in living soybean cotyledons. Results from a time course study indicated that maximum concentrations of the phytoalexin glyceollin, 955 microg/g fresh weight (fw), occurred at day 3 in soybean cotyledon tissue inoculated with A. sojae. Other Aspergillus species caused an accumulation of glyceollin at significantly lower levels. A maximum concentration of coumestrol of 27.2 microg/g fw was obtained from soybean cotyledons inoculated with A. niger. Soybean phytoalexins induced by food-grade A. sojae and A. oryzae allowed the collection of higher concentrations of phytoalexins for further examination in several in vitro and in vivo biological studies conducted to determine potential estrogenic activities.     

Direct and indirect effects of enhanced UV-B radiation on the decomposing and competitive abilities of saprobic fungi

Increases in UV-B radiation have been shown to slow the rate of litter decomposition in ecosystems. However, it is unclear if this is a result of direct UV-B effects on saprobic microorganisms, or a result of UV-B-induced changes in litter quality that indirectly affect decay by saprobes. In this study, we evaluated the magnitude of direct and indirect effects on litter decomposition of Brassica napus by soil fungi, under growth chamber conditions. We found that, both, direct and indirect UV-B negatively influenced litter decomposition, however, direct effects were much more pronounced. We then tested whether UV-B radiation would have species-specific effects on fungal colonization and competitive ability, rather than influencing all fungal species equally. We predicted that darkly pigmented fungi would increase their relative competitive ability under high UV-B. The test fungi were all isolated from field soil under Brassica napus. Two fungi were hyaline (Aspergillus terreus, Trichoderma koningii), two were darkly-pigmented (Cladosporium sphaerospermum, Epicoccum purpurascens) and one had a hyaline mycelium but darkly-pigmented conidia (Aspergillus niger). Elevated UV-B radiation had differential direct and indirect effects on fungal growth, and caused shifts in the competitive balances between pigmented and non-pigmented fungi. However, in only two of six pair-wise challenges did the pigmented species increase their relative competitive ability under UV-B conditions. It is clear that UV-B profoundly influence fungal community structure in soil, but the direction of such effects remains unpredictable.     

Astigmatid mite growth and fungi preference (Acari: Acaridida): Comparisons in laboratory experiments

The relationship between palatability and suitability of fungi for sustaining mite population growth was tested in the laboratory. The effect of mite fungal preference on spore dispersion was also studied. Eight species of microscopic fungi, Alternaria alternata, Aspergillus niger, Aspergillus versicolor, Cladosporium cladosporioides, Eurotium amstelodami var. amstelodami, E. amstelodami var. montevidensis, Mycocladus corymbifer, and Penicillium aurantiogriseum differed in their attractiveness as food and in their suitability to sustain population growth of three astigmatid mites, Acarus siro, Lepidoglyphus destructor and Tyrophagus putrescentiae. The preference for a particular species of fungus and its suitability for sustaining population growth were not correlated. Observed differences among mite species in their population growth were more likely associated with their ability to digest fungi. Fungi were divided into four groups based on their palatability and suitability to sustain population growth: (i) preferred food and suitable for mite growth (e.g. A. alternata, C. cladosporioides); (ii) preferred, but unsuitable (e.g. E. amstelodami var. amstelodami); (iii) avoided, but suitable (e.g. A. versicolor, M. corymbifer and E. amstelodami var. montevidensis); and (iv) avoided and unsuitable (e.g. A. niger). With respect to fungal spore dispersion, mites had the least effect on “avoided and unsuitable” fungal species while preferred fungi were most influenced by mite grazing.