Lignocellulolytic enzyme profiles of edible mushroom fungi

Lentinula edodes lignocellulolases and lipases produced in Macaúba residue and use of the enzymatic extract in the degradation of textile dyes

Agro-industrial residue and textile effluents have caused environmental damage to soil and water bodies. The production of fungal enzymes using agro-industrial residues and the use of these enzymes in the degradation of textile dyes can be a viable alternative to reduce these environmental damages. Lentinula edodes is a white rot fungus with high nutritional value that produces edible mushrooms and enzymes of commercial interest. Thus, the objectives of this study were to produce, purify, and biochemically characterize the lignocellulolytic enzymes and lipases produced for L. edodes in Macaúba coconut and to evaluate their potential for the degradation of textile dyes. The L. edodes UFV 73 had maximum enzymatic activity at 37 days of incubation. After the purification steps, the laccase, manganese peroxidase (MnP), cellulase, and, xylanase yields were 489.01, 264.2, 105.02, and 9.5%. The optimum temperature of cellulase activity did not change from 4 to 60 °C. The MnP, laccase, and lipase had activity directly proportional to the increase in temperature, while the cellulase and xylanase activity did not change. The optimum pH varied among analyzed enzymes. All the enzymes analyzed are according to Michaelis-Menten kinetics. The lignocellulolytic enzymes were stable up to 8 h of incubation and lipase had a reduction of activity after one hour. The discoloration rate of indigo dye by partially purified enzymatic extract (PPPE) was 40%, which shows its potential for degradation of dyes from textile industries.

Textile azo dyes discolouration using spent mushroom substrate: enzymatic degradation and adsorption mechanisms

This study evaluated the adsorption and enzymatic degradation of azo dyes when using SMS. The laccase present in the SMS was characterised, and the maximum activity was obtained at pH 2, a temperature of 45°C, a Michaelis-Menten constant (Km) of 0.264 mM, and a maximum reaction rate (Vmax) of 117.95 µmol L-1 min-1. The presence of NaCl at 5 mM inhibited enzyme activity while no inhibition was observed by Na2SO4, typically found in textile wastewater. The maximum dye adsorption (57.22%) was achieved at pH 8.0, 25°C, and 100 g L-1 of SMS while the maximum enzymatic degradation (14.18%) was obtained under the same conditions, except at pH 4.0. The enzymes laccase, lignin peroxidase, and manganese peroxidase trapped in the SMS resulted in higher dye discolouration when compared to that extracted with aqueous solution, meaning that SMS has strong adsorption capacity and is a natural immobilisation matrix, which improves the enzymatic degradation of the dyes. Thus, SMS can be used in the treatment of textile effluents for dye removal by simultaneous mechanisms of adsorption and enzymatic degradation, with reduction of environmental impacts for SMS disposal and reduction of the costs associated with commercial enzymes and adsorbents.

Physiological changes and gene responses during Ganoderma lucidum growth with selenium supplementation

Ganoderma lucidum basidiomycota is highly appreciated for its health and nutrition value. In the present study, Ganoderma lucidum was cultivated as selenium transformation carrier, and the physiological changes and gene responses by selenium supplementation were revealed through high-throughput RNA-Seq technology. As a result, selenium supplementation increased the stipe length and the cap size, but decreased the cap thickness of G. lucidum. Mineral salt supplementation could greatly promote the formation of triterpene acids and selenium in G. lucidum. The highest yield was gained in the treatment with selenium content of 200 µg/g. Subsequently, the tissues of G. lucidum at budding and mature stages in this treatment group were sampled for transcriptome analysis and compared to those of a control group without selenium supplementation. A total of 16,113 expressed genes were obtained from the transcriptome of G. lucidum, and GO-annotated unigenes were mainly involved in molecular functions and KEGG-annotated ones were highly expressed in ribosomal pathway. Furthermore, genes involved in carbon metabolism pathway were most promoted by selenium at budding stage of G. lucidum, while gene expression was the highest in the pathway of amino acid biosynthesis at mature stage of G. lucidum. Specially, selenium-related genes in G. lucidum, such as GL23172-G, GL29881-G and GL28298-G, played a regulatory role in oxidoreductase, antioxidant activity and tryptophan synthesis. The results provide a theoretical basis for further study of selenium-enriched mushrooms and aid to development of Se-enriched foodstuff and health products made from fungi.

Bioconversion of bamboo shoot shells through the cultivation of the edible mushrooms Volvariella volvacea

Bamboo shoot shell (BSS), as agricultural waste, is mostly burned or discarded, causing serious environment pollution. In this study, the degradation and utilization of BSS by the edible fungus Volvariella Volvacea was investigated. The composition of V. volvacea fruit body was determined by HPLC-MS, GC-MS and ICP-OES. The activities of CMCase and xylanase were monitored by DNS (3,5-dinitrosalicylic acid) method. Laccase activity was assayed by the oxidation reaction of ABTS [2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate)]. The degraded bamboo shoot shell powder was characterized by FTIR and SEM. The results showed that the mycelium of V. volvacea could degrade and utilize BSS for growth. The activities of carboxymethyl cellulase and laccase were increased during the cultivation. At the same time, the physical structure of the shell fiber becames porous and rough. Most of the products of decayed fibers contain alkanes, ethyl or methyl groups. Moreover, the biological efficiency (fruiting body yield) of V. volvacea cultivated on BSS was 1.52-fold higher than that of straw cultivation. The contents of total lipid, elaidic acid (C18:1n-9), total essential amino acids, total amino acids and iron in V. volvacea fruit bodies grown on BSS were 1.11, 1.66, 1.52, 1.60 and 1.30-fold higher than those of straw treatment, respectively. This study provides an effective method to solve the environmental pollution caused by BSS, and provides a new way for the potential utilization of BSS in edible fungi cultivation.

Chemical Proprieties of Biopolymers (Chitin/Chitosan) and Their Synergic Effects with Endophytic Bacillus Species: Unlimited Applications in Agriculture

Over the past decade, reckless usage of synthetic pesticides and fertilizers in agriculture has made the environment and human health progressively vulnerable. This setting leads to the pursuit of other environmentally friendly interventions. Amongst the suggested solutions, the use of chitin and chitosan came about, whether alone or in combination with endophytic bacterial strains. In the framework of this research, we reported an assortment of studies on the physico-chemical properties and potential applications in the agricultural field of two biopolymers extracted from shrimp shells (chitin and chitosan), in addition to their uses as biofertilizers and biostimulators in combination with bacterial strains of the genus Bacillus sp. (having biochemical and enzymatic properties).

Comprehensive studies on optimization of ligno-hemicellulolytic enzymes by indigenous white rot hymenomycetes under solid-state cultivation using agro-industrial wastes

The disposal of oil palm biomass is a huge challenge in Malaysian oil palm plantations. The aim of this study was to develop efficient solid-state cultivated (SSC) ligno-hemicellulolytic bio-degrader formulations of indigenous white-rot hymenomycetes (Trametes lactinea FBW and Pycnoporus sanguineus FBR) utilizing oil palm empty fruit bunches (EFB), rubber wood sawdust (SD) and vermiculite (V) either alone or in combination as substrates. Based on significant laccase (849.40 U mg^-1 protein), xylanase (42.26 U g^-1 protein) and amylase (157.49 U g^-1 protein) production, SD+V (T5) and V (T3) were the optimum substrates for SSC of T. lactinea FBW. Whereas, utilizing EFB (T1) substrate for SSC of P. sanguineus FBR enhanced the production of MnP (42.51 U mg^-1 protein), LiP (103.20 U mg^-1 protein) and CMCase (34.39 U g^-1 protein), enzymes. Apparently, this is the first study reporting on the protein profiles by T. lactinea FBW, producing two isoforms of un-purified laccase (~55 and 70 kDa) and MnP (~40 and 60 kDa) and a CMCase band (~60 kDa) during SSC on SD+V (T5) substrate. Interestingly, this is also the first report to document a single isoform of un-purified laccase (~50 kDa), MnP (~45 kDa), CMCase (~60 kDa) and xylanase (~55 kDa) by P. sanguineus FBR during SSC on empty fruit bunches substrate. The computed Principal Component Analysis (PCA) Biplot analysis elucidated the relationship between the solid substrate compositions, the hymenomycete strain, ligno-hemicellulolytic enzyme profiles, and cultivation time. Therefore, it is suggested to use PCA as a tool for multivariate analysis method for comprehensive selection and optimization of ligno-hemicellulolytic enzyme cocktails by the indigenous white rot hymenomycetes. These non-toxic (acute oral toxicity) formulations are safe to be used in field applications to efficiently degrade oil palm trunks and root mass that had been felled, chipped or pulverized under zero burning waste management program. This study could also serve as an alternative method for efficient utilization of agro-industrial waste as substrates for the development of cost-effective bio-degraders formulations for agro-waste management.

Transcriptional profiling of Auricularia cornea in selenium accumulation

Auricularia cornea is a widely cultivated edible fungus with substantial nutritive value. This study aimed to enrich the multifunctional bionutrient element selenium in A. cornea to improve its quality and explore the accumulation of selenium in the fungus using high-throughput RNA-Seq technology. In general, the treatment group with a 100 µg/g supply of selenium outperformed the other treatment groups in terms of high yield, rich crude polysaccharides and a high total selenium concentration. Additional evidences demonstrated the budding and mature phases were two typical growth stages of A. cornea and were important for the accumulation of selenium. Therefore, the budding and mature phase tissues of A. cornea in the treatment group with a 100 µg/g supply of selenium were used for transcriptome analysis and compared to those of a control group that lacked additional selenium. A total of 2.56 × 105 unigenes from A. cornea transcriptome were assembled and annotated to five frequently used databases including NR, GO, KEGG, eggNOG and SwissProt. GO and KEGG pathway analysis revealed that genes involved in metabolic process and translation were up-expressed at the budding stage in response to selenium supplementation, including amino acid metabolism, lipid metabolism, ribosome. In addition, the differential gene expression patterns of A. cornea suggested that the up-expressed genes were more likely to be detected at the budding stage than at the mature stage. These results provide insights into the transcriptional response of A. cornea to selenium accumulation.

Multi-enzyme complex of white rot fungi in saccharification of lignocellulosic material

The multi-enzyme complex (crude extract) of white rot fungi Pleurotus ostreatus, Pleurotus eryngii, Trametes versicolor, Pycnosporus sanguineus and Phanerochaete chrysosporium were characterized, evaluated in the hydrolysis of pretreated pulps of sorghum straw and compared efficiency with commercial enzyme. Most fungi complexes had better hydrolysis rates compared with purified commercial enzyme.

Secreted protein extract analyses present the plant pathogen Alternaria alternata as a suitable industrial enzyme toolbox

Lignocellulosic plant biomass is the most abundant carbon source in the planet, which makes it a potential substrate for biorefinery. It consists of polysaccharides and other molecules with applications in pharmaceutical, food and feed, cosmetics, paper and textile industries. The exploitation of these resources requires the hydrolysis of the plant cell wall, which is a complex process. Aiming to discover novel fungal natural isolates with lignocellulolytic capacities, a screening for feruloyl esterase activity was performed in samples taken from different metal surfaces. An extracellular enzyme extract from the most promising candidate, the natural isolate Alternaria alternata PDA1, was analyzed. The feruloyl esterase activity of the enzyme extract was characterized, determining the pH and temperature optima (pH 5.0 and 55-60 °C, respectively), thermal stability and kinetic parameters, among others. Proteomic analyses derived from two-dimensional gels allowed the identification and classification of 97 protein spots from the extracellular proteome. Most of the identified proteins belonged to the carbohydrates metabolism group, particularly plant cell wall degradation. Enzymatic activities of the identified proteins (β-glucosidase, cellobiohydrolase, endoglucanase, β-xylosidase and xylanase) of the extract were also measured. These findings confirm A. alternata PDA1 as a promising lignocellulolytic enzyme producer.

SIGNIFICANCE

Although plant biomass is an abundant material that can be potentially utilized by several industries, the effective hydrolysis of the recalcitrant plant cell wall is not a straightforward process. As this hydrolysis occurs in nature relying almost solely on microbial enzymatic systems, it is reasonable to infer that further studies on lignocellulolytic enzymes will discover new sustainable industrial solutions. The results included in this paper provide a promising fungal candidate for biotechnological processes to obtain added value from plant byproducts and analogous substrates. Moreover, the proteomic analysis of the secretome of a natural isolate of Alternaria sp. grown in the presence of one of the most used vegetal substrates on the biofuels industry (sugar beet pulp) sheds light on the extracellular enzymatic machinery of this fungal plant pathogen, and can be potentially applied to developing new industrial enzymatic tools. This work is, to our knowledge, the first to analyze in depth the secreted enzyme extract of the plant pathogen Alternaria when grown on a lignocellulosic substrate, identifying its proteins by means of MALDI-TOF/TOF mass spectrometry and characterizing its feruloyl esterase, cellulase and xylanolytic activities.

Mushrooms as Efficient Solar Steam-Generation Devices

Solar steam generation is emerging as a promising technology, for its potential in harvesting solar energy for various applications such as desalination and sterilization. Recent studies have reported a variety of artificial structures that are designed and fabricated to improve energy conversion efficiencies by enhancing solar absorption, heat localization, water supply, and vapor transportation. Mushrooms, as a kind of living organism, are surprisingly found to be efficient solar steam-generation devices for the first time. Natural and carbonized mushrooms can achieve ≈62% and ≈78% conversion efficiencies under 1 sun illumination, respectively. It is found that this capability of high solar steam generation is attributed to the unique natural structure of mushroom, umbrella-shaped black pileus, porous context, and fibrous stipe with a small cross section. These features not only provide efficient light absorption, water supply, and vapor escape, but also suppress three components of heat losses at the same time. These findings not only reveal the hidden talent of mushrooms as low-cost materials for solar steam generation, but also provide inspiration for the future development of high-performance solar thermal conversion devices.

Synergetic effect of rhamnolipid from Pseudomonas aeruginosa C1501 and phytotoxic metabolite from Lasiodiplodia pseudotheobromae C1136 on Amaranthus hybridus L. and Echinochloa crus-galli weeds

Rhamnolipid (Rh) is a biosurfactant produced by the bacterial Pseudomonas aeruginosa. This present study investigates rhizospheric strain C1501 of P. aeruginosa with an accession number KF976394 with the best production of rhamnolipid: a biosurfactant. The partially purified rhamnolipid from strain C1501 and Tween 80 was tested on mycelial growth of wild strain C1136. The enzyme activities involved in biodegradation, as well as necrosis induction on the tested weeds, were performed using scanning electron microscopy. It was observed that the different concentrations of rhamnolipid tested enhanced the dry mycelia weight yield of Lasiodiplodia pseudotheobromae which has been established to be producing a phytotoxic metabolite for killing weeds. It was observed that strain C1136 had a high level of cellulase and xylanase enzyme activities during this study. The scanning electron microscopy showed that the mutant strain of C1136 combined with 0.003% v/v of rhamnolipid enhances biodegradability and a high level of necrosis on the tested weeds compared with that on the untreated weeds. The highest CMCase activities and xylanase activities were obtained on the fourth day from the phytotoxic metabolite produced from the mutant strain of L. pseudotheobromae when combined with 0.003% v/v of rhamnolipid. This study has shown that rhamnolipid can serve as an adjuvant in order to enhance the penetrability of bioherbicide active ingredient for controlling weeds.

Purification and characterization of a novel ginsenoside Rc-hydrolyzing β-glucosidase from Armillaria mellea mycelia

Ginsenosides are the principal compounds responsible for the pharmacological effects and health benefits of Panax ginseng root. Among protopanaxadiol (PPD)-type ginsenosides, minor ginsenosides such as ginsenoside (G)-F2, G-Rh2, compound (C)-Mc1, C-Mc, C-O, C-Y, and C-K are known to be more pharmacologically active constituents than major ginsenosides such as G-Rb1, G-Rb2, G-Rc, and G-Rd. A novel ginsenoside Rc-hydrolyzing β-glucosidase (BG-1) from Armillaria mellea mycelia was purified as a single protein band with molecular weight of 121.5 kDa on SDS-PAGE and a specific activity of 17.9 U mg-1 protein. BG-1 concurrently hydrolyzed α-(1 → 6)-arabinofuranosidic linkage at the C-20 site or outer β-(1 → 2)-glucosidic linkage at the C-3 site of G-Rc to produce G-Rd and C-Mc1, respectively. The enzyme also hydrolyzed outer and inner glucosidic linkages at the C-3 site of G-Rd to produce C-K via G-F2, and inner glucosidic linkage at the C-3 site of C-Mc1 to produce C-Mc. C-Mc was also slowly hydrolyzed α-(1 → 6)-arabinofuranosidic linkage at the C-20 site to produce C-K with reaction time prolongation. Finally, the pathways for formation of C-Mc and C-K from G-Rc by BG-1 were G-Rc → C-Mc1 → C-Mc and G-Rc → G-Rd → G-F2 → C-K, respectively. The optimum reaction conditions for C-Mc and C-K formation from G-Rc by BG-1 were pH 4.0-4.5, temperature 45-60 °C, and reaction time 72-96 h. This is the first report of efficient production of minor ginsenosides, C-Mc and C-K from G-Rc by β-glucosidase purified from A. mellea mycelia.

Production of Oxidative and Hydrolytic Enzymes by Coprinus cinereus (Schaeff.) Gray from Sisal Wastes Supplemented with Cow Dung Manure

The activity of oxidative and hydrolytic enzymes of the edible and medicinal white rot fungi Coprinus cinereus (Schaeff.) Gray mushroom was observed during mycelia growth and fruiting body development in solid substrate fermentation using sisal waste fractions amended with cow dung manure as supplement. Laccase had the highest titre value among the five detected enzymes. Its activity was higher during mycelia growth compared to fruiting phase, with 10% supplemented substrate formulation unmixed sisal leaf decortication residues [abbreviated SL : SB (100 : 0)] displaying the highest activity of 39.45 ± 12.05 Ug⁻¹. Lignin peroxidase (LiP) exhibited a characteristic wave-like pattern with the highest peaks found either during full mycelia colonization or soon after first flush harvest; the highest activity of 1.93 ± 0.62 Ug⁻¹ was observed on unsupplemented SL : SB (100 : 0) substrate formulation during mycelia colonization. For hydrolytic enzymes, the highest carboxymethyl cellulase (CMCase) activity of 2.03 ± 0.70 Ug⁻¹ was observed on 20% supplemented SL : SB (0 : 100) after first flush; that of pectinase (1.90 ± 0.32 Ug⁻¹) was revealed after third flush on 10% supplemented SL : SB (0 : 100) substrate formulation while 10% supplemented SL : SB (25 : 75) exhibited the highest xylanase activity (1.23 ± 0.12 Ug⁻¹) after first flush. These findings show that the activities of both oxidative and hydrolytic enzymes were regulated in line with developmental phase of growth of Coprinus cinereus.

Enzymatic formation of compound-K from ginsenoside Rb1 by enzyme preparation from cultured mycelia of Armillaria mellea

Background

Minor saponins or human intestinal bacterial metabolites, such as ginsenosides Rg3, F2, Rh2, and compound K, are more pharmacologically active than major saponins, such as ginsenosides Rb1, Rb2, and Rc. In this work, enzymatic hydrolysis of ginsenoside Rb1 was studied using enzyme preparations from cultured mycelia of mushrooms.

Methods

Mycelia of Armillaria mellea, Ganoderma lucidum, Phellinus linteus, Elfvingia applanata, and Pleurotus ostreatus were cultivated in liquid media at 25°C for 2 wk. Enzyme preparations from cultured mycelia of five mushrooms were obtained by mycelia separation from cultured broth, enzyme extraction, ammonium sulfate (30–80%) precipitation, dialysis, and freeze drying, respectively. The enzyme preparations were used for enzymatic hydrolysis of ginsenoside Rb1.

Results

Among the mushrooms used in this study, the enzyme preparation from cultured mycelia of A. mellea (AMMEP) was found to convert ginsenoside Rb1 into compound K with a high yield, while those from G. lucidum, P. linteus, E. applanata, and P. ostreatus produced remarkable amounts of ginsenoside Rd from ginsenoside Rb1. The enzymatic hydrolysis pathway of ginsenoside Rb1 by AMMEP was Rb1 → Rd → F2 → compound K. The optimum reaction conditions for compound K formation from ginsenoside Rb1 were as follows: reaction time 72–96 h, pH 4.0–4.5, and temperature 45–55°C.

Conclusion

AMMEP can be used to produce the human intestinal bacterial metabolite, compound K, from ginsenoside Rb1 with a high yield and without food safety issues.

Sequencing and comparative analysis of the straw mushroom (Volvariella volvacea) genome

Volvariella volvacea, the edible straw mushroom, is a highly nutritious food source that is widely cultivated on a commercial scale in many parts of Asia using agricultural wastes (rice straw, cotton wastes) as growth substrates. However, developments in V. volvacea cultivation have been limited due to a low biological efficiency (i.e. conversion of growth substrate to mushroom fruit bodies), sensitivity to low temperatures, and an unclear sexuality pattern that has restricted the breeding of improved strains. We have now sequenced the genome of V. volvacea and assembled it into 62 scaffolds with a total genome size of 35.7 megabases (Mb), containing 11,084 predicted gene models. Comparative analyses were performed with the model species in basidiomycete on mating type system, carbohydrate active enzymes, and fungal oxidative lignin enzymes. We also studied transcriptional regulation of the response to low temperature (4°C). We found that the genome of V. volvacea has many genes that code for enzymes, which are involved in the degradation of cellulose, hemicellulose, and pectin. The molecular genetics of the mating type system in V. volvacea was also found to be similar to the bipolar system in basidiomycetes, suggesting that it is secondary homothallism. Sensitivity to low temperatures could be due to the lack of the initiation of the biosynthesis of unsaturated fatty acids, trehalose and glycogen biosyntheses in this mushroom. Genome sequencing of V. volvacea has improved our understanding of the biological characteristics related to the degradation of the cultivating compost consisting of agricultural waste, the sexual reproduction mechanism, and the sensitivity to low temperatures at the molecular level which in turn will enable us to increase the industrial production of this mushroom.

Use of spent mushroom substrates from Agaricus subrufescens (syn. A. blazei, A. brasiliensis) and Lentinula edodes productions in the enrichment of a soil-based potting media for lettuce (Lactuca sativa) cultivation: Growth promotion and soil bioremediation

This study aimed to assess physicochemical and microbiological properties of fresh spent mushroom substrates (SMSs)--without post-crop heat treatment--from Agaricus subrufescens and Lentinula edodes production to optimize the use of these residues in the soil enrichment for lettuce growth promotion and soil remediation. Organic matter and C content of both SMSs were high. Fresh A. subrufescens SMS was a good source of N, P and K. On the other hand, L. edodes SMS presented a lower concentration of these nutrients and a high level of immaturity. Both SMSs presented high electric conductivity values (2.5-3.4 mS/cm). Microbiological analysis, based upon enumeration of culturable bacteria (thermophilic and mesophilic) and fungi, and also evolution of CO(2), showed that SMSs played higher microbial diversity than soil control. Laccase activity from A. subrufescens SMS tended to remain constant during a 2-month period, while L. edodes SMS presented low laccase activity throughout the same period. Agaricus subrufescens and L. edodes were able to grow on a PDA (Potato Dextrose Agar) media supplemented with different concentrations of atrazine (1-50 microg/ml), degraded the herbicide, attaining rates of 35% and 26%, respectively. On experiments of lettuce growth promotion using a soil-based potting media with different SMS rates, 5% and 10% (dw) rates of A. subrufescens SMS resulted in higher lettuce aerial dry weights than the rates of 25% and 40%, the chemical fertilization (NPK) and the control (soil). At 10% supplementation, lettuce aerial dry weight increased 2.2 and 1.3 times compared to the control and the NPK treatment, respectively. Protein content increased along with SMS rates. Fresh A. subrufescens SMS was an excellent supplement for lettuce growth promotion and showed potential for remediation of biocides possibly due to improved microbial diversity and enzymatic activity. Fresh L. edodes SMS was not a good fertilizer, at least under the conditions tested. However, microbiological analysis showed that promising results may be achieved when using fresh L. edodes SMS for soil remediation.

Optimizing edible fungal growth and biodegradation of inedible crop residues using various cropping methods

Long-term manned space flights to Mars require the development of an advanced life support (ALS) ecosystem including efficient food crop production, processing and recycling waste products thereof. Using edible white rot fungi (EWRF) to achieve effective biomass transformation in ALS requires optimal and rapid biodegradative activity on lignocellulosic wastes. We investigated the mycelial growth of Lentinula edodes and Pleurotus ostreatus on processed residues of various crops under various cropping patterns. In single cropping, mycelial growth and fruiting in all strains were significantly repressed on sweet potato and basil. However, growth of the strains was improved when sweet potato and basil residues were paired with rice or wheat straw. Oyster mushroom (Pleurotus) strains were better than shiitake (L. edodes) strains under single, paired, and mixed cropping patterns. Mixed cropping further eliminated the inherent inhibitory effect of sweet potato, basil, or lettuce on fungal growth. Co-cropping fungal species had a synergistic effect on rate of fungal growth, substrate colonization, and fruiting. Use of efficient cropping methods may enhance fungal growth, fruiting, biodegradation of crop residues, and efficiency of biomass recycling.

Differential degradation of oak (Quercus petraea) leaf litter by litter-decomposing basidiomycetes

Due to production of lignocellulose-degrading enzymes, saprotrophic litter-decomposing basidiomycetes can significantly contribute to the turnover of soil organic matter. The production of lignin and polysaccharide-degrading enzymes and changes in the chemical composition of litter was studied with Marasmius quercophilus, Mycena inclinata and Pholiota lenta, three basidiomycete species typical of oak (Quercus petraea) forests. Within 12weeks of incubation, M. inclinata decomposed 33%, M. quercophilus 36% and P. lenta 48% of the substrate dry mass. All fungi produced laccase and Mn-peroxidase and none of them produced lignin peroxidase or Mn-independent peroxidases. M. inclinata and M. quercophilus produced considerable laccase activity, while production by P. lenta was low. M. quercophilus and P. lenta produced most Mn-peroxidase at the beginning of the experiment, while the production by M. inclinata was more stable in time. Endo-1,4-beta-xylanase exhibited the highest activity among endocleaving glycosyl hydrolases while 1,4-beta-glucosidase was the main exocleaving enzyme. All fungi decreased the C:N ratio of the litter from 27 to 13-17 and M. inclinata and M. quercophilus also decreased the lignin content. Analytical pyrolysis of decayed litter showed changes in litter composition similar to those caused by white-rot fungi during wood decay, e.g. a decrease in the syringyl/guaiacyl lignin ratio. These changes were more pronounced in M. inclinata and M. quercophilus. The results indicate that different litter-decomposing fungi can cause substantial litter transformation despite considerable differences in the production of lignocellulose-degrading enzymes.

Cloning of multiple cellulase cDNAs fromVolvariella volvaceaand their differential expression during substrate colonization and fruiting

We used PCR-based methods to clone and sequence four previously unidentified cellulase cDNAs: cbhI-I, cbhI-II, cbhII-I and egII. CbhI-I, cbhI-II and cbhII-I consist of 1710, 1610 and 1453 bp, respectively, and encode for 512, 458 and 442 amino acids, respectively. EgII consists of 1180 bp encoding for 310 amino acids, and belongs to family 61 of the glycosyl hydrolases. CbhI-I, cbhII-I and egII all have a modular structure, with the catalytic domain (CD) and cellulose-binding domain (CBD) located at the C-terminus in cbhI-I and egII, and at the N-terminus in cbhII-I. CbhI-II shows high homology to cbhI-I but lacks a CBD. Northern blotting revealed that cbhI-I, cbhI-II and cbhII-I were coordinately expressed at various stages of the mushroom developmental cycle (substrate colonization to mature fruit body), although the number of cbhI-I transcripts was much smaller. No egII expression was detectable during the substrate colonization phase but transcription levels increased as fruit body morphogenesis progressed.

Tuber borchii fruit body: 2-dimensional profile and protein identification

The formation of the fruit body represents the final phase of the ectomycorrhizal fungus T. borchii life cycle. Very little is known concerning the molecular and biochemical processes involved in the fructification phase. 2-DE maps of unripe and ripe ascocarps revealed different protein expression levels and the comparison of the electropherograms led to the identification of specific proteins for each developmental phase. Associating micropreparative 2-DE to microchemical approaches, such as N-terminal sequencing and 2-D gel-electrophoresis mass-spectrometry, proteins playing pivotal roles in truffle physiology were identified.

Endoglucanase I from the edible straw mushroom, Volvariella volvacea. Purification, characterization, cloning and expression

We isolated an endoglucanase, EG1, from culture fluid of Volvariella volvacea grown on crystalline cellulose by ion-exchange and gel filtration chromatography, and preparative PAGE. EG1 has a molecular mass of 42 kDa as determined by SDS/PAGE and an isoelectric point of 7.7. Enzyme-catalysed hydrolysis of carboxymethyl-cellulose (CM-cellulose) is maximal at pH 7.5 and 55 degrees C. EG1 also hydrolysed phosphoric acid-swollen cellulose and filter paper (at rates of 29% and 6%, respectively, compared with CM-cellulose), but did not hydrolyse crystalline cellulose, cotton, oat spelt xylan, and birchwood xylan. Degenerate primers based on the N-terminal sequences of purified EGI and a protease-generated fragment were used to generate cDNA fragments encoding a portion of the EG1 gene (eg1), and RACE was used to obtain full-length cDNA clones. The cDNA of eg1 contained an ORF of 1167 bp encoding 389 amino acids. The amino-acid sequence from Ala24 to Thr40 corresponded to the N-terminal sequence of the purified protein. The first 23 amino acids are presumed to be a signal peptide. V. volvacea EG1 has been assigned to glycoside hydrolase family 5 according to the classification of glycohydrolases based on amino-acid sequence similarities. Transcripts of eg1 were detected in total RNA from mycelium grown on cellulose but not from mycelium grown on glucose. Cellobiose also induced eg1 expression in 1- to 4-day-old cultures but the signal intensity was lower than that obtained with cellulose. Catabolite repression was observed 24 h after addition of 1% (w/v) glucose, alpha-lactose, beta-lactose, xylose, mannose, sorbose or fructose to medium containing 1% (w/v) crystalline cellulose. Eg1 was expressed at a high level in the yeast, Pichia pastoris, and the catalytic activity of the recombinant EG1 was confirmed.

Production, characterization and properties of polysaccharide depolymerizing enzymes from a strain of Curvularia inaequalis

Xylanase, beta-glucosidase, beta-xylosidase, endoglucanase and polygalacturonase production from Curvularia inaequalis was carried out by means of solid-state and submerged fermentation using different carbon sources. beta-Glucosidase, beta-xylosidase, polygalacturonase and xylanase produced by the microorganisms were characterized. beta-Glucosidase presented optimum activity at pH 5.5 whereas xylanase, polygalacturonase and beta-xylosidase activities were optimal at pH 5.0. Maximal activity of beta-glucosidase was determined at 60 degrees C, beta-xylosidase at 70 degrees C, and polygalacturonase and xylanase at 55 degrees C. These enzymes were stable at acidic to neutral pH and at 40-45 degrees C. The crude enzyme solution was studied for the hydrolysis of agricultural residues.

Production and distribution of endoglucanase, cellobiohydrolase, and beta-glucosidase components of the cellulolytic system of Volvariella volvacea, the edible straw mushroom

The edible straw mushroom, Volvariella volvacea, produces a multicomponent enzyme system consisting of endo-1,4-beta-glucanase, cellobiohydrolase, and beta-glucosidase for the conversion of cellulose to glucose. The highest levels of endoglucanase and cellobiohydrolase were recorded in cultures containing microcrystalline cellulose (Avicel) or filter paper, while lower but detectable levels of activity were also produced on carboxymethyl cellulose, cotton wool, xylitol, or salicin. Biochemical analyses of different culture fractions in cultures exhibiting peak enzyme production revealed that most of the endoglucase was present either in the culture filtrate (45.8% of the total) or associated with the insoluble pellet fraction remaining after centrifugation of homogenized mycelia (32.6%). Cellobiohydrolase exhibited a similar distribution pattern, with 58.9% of the total enzyme present in culture filtrates and 31.0% associated with the pellet fraction. Conversely, most beta-glucosidase activity (63.9% of the total) was present in extracts of fungal mycelia whereas only 9.4% was detected in culture filtrates. The endoglucanase and beta-glucosidase distribution patterns were confirmed by confocal laser scanning microscopy combined with immunolabelling. Endoglucanase was shown to be largely cell wall associated or located extracellularly, with the highest concentrations being present in a region 1 to 2 microm wide immediately adjacent to the outer surface of (and possibly including) the hyphal wall and extending 60 to 70 microm from the hyphal tip. Immunofluorescence patterns indicated little if any intracellular endoglucanase. Most beta-glucosidase was located intracellularly in the apical area extending 60 to 70 microm below the hyphal tip, although enzyme was also evident in the extracellular region extending approximately 15 microm all around the hyphal tip and trailing back along the length of the hypha. The regions of the hypha located some distance from the apical region appeared to be devoid of intracellular beta-glucosidase, and the enzyme appears to be associated almost exclusively with, or located on the outside surface of, the hyphal wall.