Use of Ozone as a Substrate Treatment for the Control of Trichoderma in the Production of Pleurotus ostreatus

Pleurotus ostreatus is one of the most widely cultivated species in the world. It can be produced in many lignocellulosic substrates after carrying out a treatment to eliminate competing microorganisms. The most commonly used is pasteurization by steam or by immersion in hot water. The aim of this work is to evaluate if ozone can be employed as treatment for decontamination of the substrate used for the production of the edible mushroom P. ostreatus to control of green mold Trichoderma. Wheat straw was employed as a substrate. We used two different methodologies: bubbling ozone into a tank with water and the substrate, and injecting ozone into a closed tank with the substrate inside. Ten treatments were carried out including two treatments with inoculation by a spray of conidia of Trichoderma. The effect of ozone on the conidia was also evaluated. We found that the treatment of the substrate with ozone in immersed water resulted more effective (lower growth of Trichoderma) than injecting ozone into a closed tank. Anyway, we found that the contaminant fungi could grow on the substrate in both treatments with ozone. We observed that although ozone affected the conidia when it was bubbled into water, some of them still managed to survive and could germinate 72 h later. P. ostreatus could grow and produce fruiting bodies on a substrate that was previously treated with ozone and yields were not affected. Based on the results obtained, we conclude that ozone may not be an effective agent to control Trichoderma in highly contaminated substrates, at least in the experimental conditions that we used, for the production of P. ostreatus.

Solid-state bioprocessing of sugarcane bagasse with Auricularia fuscosuccinea for phenolic compounds extraction

Sugarcane bagasse is a natural source of phenolic compounds. However, these compounds are bound to lignocellulose components, reducing their ability to function as good antioxidants. These linkages are hydrolyzed by enzymes like β-glucosidases, increasing free phenolics. Auricularia is a food-grade genus capable of producing β-glucosidases. The aim of this work was (I) to determine naturally occurring species of Auricularia and (II) to obtain phenolic compounds through the solid-state bioprocessing of sugarcane bagasse. We have successfully isolated five strains that were assigned to the taxon A. fuscosuccinea. We determined β-glucosidase activity by fluorescence plate assay of the five isolated strains and adjusted an optimal temperature for mycelial growth at 30 °C. A. fuscosuccinea LBM 243 was chosen for solid-state bioprocessing of sugarcane bagasse. β-glucosidase activity (12.2 ± 0.62 U l^-1) and protein content (51.58 ± 6.26 mg l^-1) were highest on day 20 of culture. The maximum value of total phenolic content (507.5 ± 9.05 mg l^-1) was obtained at day 20 and antioxidant capacity (34.44% ± 11.20) was highest at day 10, both in ethanolic extracts. The best performance of ethanol against methanol extraction in this work is highlighted considering ethanol to be a safe, efficient, and low-cost solvent.

Towards an Optimal Methodology for Basidiomes Production of Naturally Occurring Species of the Genus Oudemansiella (Basidiomycetes)

Oudemansiella species are worldwide distributed and they are characterized for having attractive appearance, a soft fleshy context and mild taste and odor, what makes them interesting for mushroom intensive production. However, studies on their cultivation are scarce and there is no information regarding productive and morphological parameters of fruiting bodies obtained in culture. Here, we propose a methodology to determine the best production technique for the cultivation of not only Oudemansiella species but also of other xylophagous species assaying five different mushroom cultivation systems. Also, the optimal temperature of vegetative growth, the optimal lignocellulosic substrates and the nutritional properties of two naturally occurring Oudemansiella species were determined. As a result, bags with holes-system proved to be the most appropriate technique for the production of fruiting bodies, 25 °C was determined as the optimal temperature for mycelial growth and wheat straw as the best substrate. The evaluated species showed a higher content of fats and fiber and a lower content of proteins and carbohydrates compared to other mushrooms. Furthermore, this is the first report of the cultivation of O. cubensis on agricultural wastes in the world.

Revision of the genera Agrocybe and Cyclocybe (Strophariaceae, Agaricales, Basidiomycota) in Argentina

Abstract Agrocybe is characterized by the collybioid to tricholomatoid basidiomata with rusty to dark spore-print, a hymeniform pileipellis, and basidiosspores with a reduced to broad germ-pore. Recently, the species with reduced germ-pore were segregated to Cyclocybe. The knowledge of these genera in Argentina is scanty, although they have been partially studied in the country, but there is not a field that deals exhaustively with it. Macro- and micromorphological characters of specimens obtained in the feld and from different national herbaria (BAFC, CTES, LIL, LPS) were analyzed. Cultivation techniques were used to obtain basidiomata, allowing for a macro- and micromorphological study of fresh developing basidiomes. We concluded that in Argentina there are, so far, 14 species of Agrocybe (one of them with 3 varieties) and two of Cyclocybe including to C. wrightii, which is proposed as a new combination. Sixteen species are described and a key to the Argentinian species of Agrocybe and Cyclocybe is proposed.

Considerations and consequences of allowing DNA sequence data as types of fungal taxa

Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.

A Comparative Study of New Aspergillus Strains for Proteolytic Enzymes Production by Solid State Fermentation

A comparative study of the proteolytic enzymes production using twelve Aspergillus strains previously unused for this purpose was performed by solid state fermentation. A semiquantitative and quantitative evaluation of proteolytic activity were carried out using crude enzymatic extracts obtained from the fermentation cultures, finding seven strains with high and intermediate level of protease activity. Biochemical, thermodynamics, and kinetics features such as optimum pH and temperature values, thermal stability, activation energy (E a), quotient energy (Q 10), K m , and V max were studied in four enzymatic extracts from the selected strains that showed the highest productivity. Additionally, these strains were evaluated by zymogram analysis obtaining protease profiles with a wide range of molecular weight for each sample. From these four strains with the highest productivity, the proteolytic extract of A. sojae ATCC 20235 was shown to be an appropriate biocatalyst for hydrolysis of casein and gelatin substrates, increasing its antioxidant activities in 35% and 125%, respectively.

Efficiency of treatments for controlling Trichoderma spp during spawning in cultivation of lignicolous mushrooms

Trichoderma spp is the cause of the green mold disease in mushroom cultivation production. Many disinfection treatments are commonly applied to lignocellulose substrates to prevent contamination. Mushroom growers are usually worried about the contaminations that may occur after these treatments during handling or spawning. The aim of this paper is to estimate the growth of the green mold Trichoderma sp on lignocellulose substrates after different disinfection treatments to know which of them is more effective to avoid contamination during spawning phase. Three different treatments were assayed: sterilization (121 °C), immersion in hot water (60 and 80 °C), and immersion in alkalinized water. Wheat straw, wheat seeds and Eucalyptus or Populus sawdust were used separately as substrates. After the disinfection treatments, bagged substrates were sprayed with 3 mL of suspension of conidia of Trichoderma sp (10(5) conidia/mL) and then separately spawned with Pleurotus ostreatus or Gymnopilus pampeanus. The growth of Trichoderma sp was evaluated based on a qualitative scale. Trichoderma sp could not grow on non-sterilized substrates. Immersions in hot water treatments and immersion in alkalinized water were also unfavorable treatments for its growth. Co- cultivation with mushrooms favored Trichoderma sp growth. Mushroom cultivation disinfection treatments of lignocellulose substrates influence on the growth of Trichoderma sp when contaminations occur during spawning phase. The immersion in hot water at 60 °C for 30 min or in alkalinized water for 36 h, are treatments which better reduced the contaminations with Trichoderma sp during spawning phase for the cultivation of lignicolous species.

Microplate assay for endo-polygalacturonase activity determination based on ruthenium red method

Endo-polygalacturonase (endo-PGase) activity determinations generally rely on viscosity changes or reducing sugar ends produced by this activity over polygalacturonic acid. Torres and coworkers [Enzyme Microb. Technol. 48 (2011) 123-128] showed that ruthenium red (RR) is useful for endo-PGase determination. In this article, we present a high-throughput liquid-based endo-PGase assay based on the RR method and compare it with the viscosity determination method. The reduced assay uses a small volume of enzyme solution, 40 μg of polygalacturonic acid, and 45 μg of RR for each sample determination. Furthermore, we obtained an interconversion factor for RR and viscosity activities.

Checklist of the Argentine Agaricales 7. Cortinariaceae and Entolomataceae

A checklist of species belonging to the families Cortinariaceae and Entolomataceae was made for Argentina. The list includes all species published until the year 2012. Nineteen genera and 444 species were recorded, 370 species from the family Cortinariaceae and 74 from Entolomataceae. All of them are distributed in 19 genera, the most important being Cortinarius (240 species), Galerina (51), Entoloma (39) and Inocybe (40). With the exception of Hebeloma (13 species), Gymnopilus (12) and Clitopilus (11), the rest of the 13 genera have less than 10 species each. Galeropsis, Locellina, Nolanea and Pseudogymnopilus have only one species recorded so far.

Heat treatment of wheat straw by immersion in hot water decreases mushroom yield in Pleurotus ostreatus

BACKGROUND

The oyster mushroom, Pleurotus ostreatus, is cultivated worldwide. It is one of the most appreciated mushrooms due to its high nutritional value. Immersion of the substrate in hot water is one of the most popular and worldwide treatment used for mushroom farmers. It is cheap and easy to implement.

AIMS

To compare the yields obtained during mushroom production of P. ostreatus using different pre-treatments (immersion in hot water, sterilization by steam and the use of fungicide) to determine if they influence mushroom crop.

METHODS

Four different treatments of substrate (wheat straw) were carried out: (i) immersion in hot water (IHW); (ii) steam sterilization; (iii) chemical; and (iv) untreated. The residual water from the IHW treatment was used to evaluate the mycelium growth and the production of P. ostreatus.

RESULTS

Carbendazim treatment produced highest yields (BE: 106.93%) while IHW produced the lowest BE with 75.83%. Sugars, N, P, K and Ca were found in residual water of IHW treatment. The residual water increased the mycelium growth but did not increase yields.

CONCLUSIONS

We have proved that IHW treatment of substrate reduced yields at least 20% when compared with other straw treatments such as steam, chemical or untreated wheat straw. Nutrients like sugars, proteins and minerals were found in the residual water extract which is the resultant water where the immersion treatment is carried out. The loss of these nutrients would be the cause of yield decrease. Alternative methods to the use of IHW as treatment of the substrate should be considered to reduce economical loss.

The genus Pleurotus in Argentina

Macro- and micromorphological characters of specimens of the genus Pleurotus (Fr.) P. Kumm. in Argentina obtained in the field and from different national herbaria were analyzed. Cultivation techniques were used to obtain basidiomata, allowing for a macro- and micromorphological study of fresh developing fruit bodies. We concluded that in Argentina there are, so far, six species, namely P. albidus, P. cystidiosus, P. ostreatus, P. pulmonarius, P. rickii and P. djamor, the latter with three varieties: var. djamor, var. cyathiformis and var. roseus.

Search for new naturally occurring strains of Pleurotus to improve yields: Pleurotus albidus as a novel proposed species for mushroom production

BACKGROUND

The species of genus Pleurotus are worldwide cultivated.

AIMS

To evaluate growth, yield production and morphological variations of fruiting bodies obtained from the cultivation of fourteen naturally occurring Pleurotus strains isolated from Argentina.

METHODS

The strains growth was tested at different temperatures on Nobles' medium. Substrates assayed were: supplemented Salix sawdust, supplemented and non supplemented wheat straw. The species studied were Pleurotus albidus, Pleurotus cystidiosus, Pleurotus djamor, Pleurotus ostreatus and Pleurotus pulmonarius.

RESULTS

The maximum rate growth was reached by strains of P. pulmonarius, P. albidus, and P. ostreatus. No relationship was found when optimal mycelium growth, incubation time and yields were compared. The highest yield was obtained with P. albidus on wheat straw (biological efficiency 171.3%) which overcame in 82% the yield obtained for the commercial strain in the same substrate. When morphological variations were analyzed for each species, significant differences were found among strains. It was also possible to find a naturally occurring strain of P. ostreatus with better biological efficiency than the commercial strain assayed.

CONCLUSIONS

We propose the study of naturally occurring strains as a useful practice to improve yields of species of Pleurotus. Due to the high biological efficiency obtained we propose P. albidus as a new species for commercial production.

Utilization of new naturally occurring strains and supplementation to improve the biological efficiency of the edible mushroom Agrocybe cylindracea

To evaluate the importance of searching new naturally occurring strains to raise yields in mushroom production, eight wild and four commercial strains of Agrocybe cylindracea were cultivated on wheat straw. The highest biological efficiencies (BE) (54.5-72.4%) were obtained with three wild and two commercial strains when cultured on non-supplemented wheat straw. Rolled oats or soybean flour supplementation were tested using three selected strains, increasing BEs up to 1.2, 0.5 and 0.7-fold, respectively. This effect of supplementation was stronger in the Asiatic wild strain, yielding up to 41.1 and 30% more than the two other strains with rolled oats and soybean flour, respectively. The Asiatic wild strain cultivated with soybean flour supplementation achieved an average biological efficiency of 179%, to our knowledge, the highest reported for this species. These results show the importance of searching for new naturally occurring strains in combination with supplemented wheat straw substrate for raising yields in A. cylindracea cultivation.

Optimal conditions for the fruit body production of natural occurring strains of Lentinus tigrinus

Lentinus tigrinus is a species with a fleshy pileus, strong odor and agreeable taste. In order to determine the optimal conditions for the production of this species, three substrates based on Salix sp. sawdust, wheat straw and supplements were tested in 500g dry weight bags at two different fruiting temperatures. Naturally occurring strains of this species were incubated at 30 degrees C. Primordium initiation could be observed 11-16 days after induction conditions began. This species produced highest yields with biological efficiency (BE) of 62% with supplemented sawdust at 25 degrees C. When bags were reduced to 100g dry weight, spawning run time was reduced from 28 to 30 to 10 to 14 days and BE increased more than 100%. L. tigrinus is a promising species with possibilities for commercial production.

Presence of different arbuscular mycorrhizal infection patterns in roots of Lotus glaber plants growing in the Salado River basin

Morphological types of arbuscular mycorrhizal (AM) fungi associated with Lotus glaber in sodic soils of the Salado River basin were studied. At least eight colonization patterns (IP) of AM fungi in roots of L. glaber were observed after 30 plants were analyzed. Arum- and Paris-type infection were found in the same plant species. This result supports the idea that AM morphology is not solely under plant control, but is also influenced by fungal identity. One infection pattern, presumably corresponding to Glomus intraradices, and a second, possibly assignable to Glomus tenue, were the most commonly found. Our results reinforce previous suggestions that G. intraradices is well adapted to sodic-saline conditions and may play a role in the resistance of L. glaber to these soils.

Presence of Pleurotus ostreatus in Patagonia, Argentina

Specimens belonging to the genus Pleurotus were collected growing on fallen trunks of Araucaria araucana, a native tree with a poorly known mycoflora, which grows in Patagonia, Argentina. Fruitbodies were produced in culture on sawdust from an isolated strain. Interspecific pairing tests performed between mating types of Pleurotus from Patagonia and tester strains of P. pulmonarius and P. ostreatus showed the Patagonia strain to be 100% compatible with P. ostreatus and incompatible with P. pulmonarius. Dikaryons obtained on sawdust were fertile, since they were able to produce fruitbodies and viable spores. This is the first documented record of P. ostreatus from Argentina and the first gilled fungus found growing on Araucaria araucana.