Growth modeling to control (in vitro) Fusarium verticillioides and Rhizopus stolonifer with thymol and carvacrol / Modelización del crecimiento in vitro para controlar Fusarium verticillioides y Rhizopus stolonifer con timol y carvacrol

The aim of this study was to evaluate the antifungal activity (in vitro) of thymol and carvacrol alone or in mixtures against Fusarium verticillioides and Rhizopus stolonifer, and to obtain primary growth models. Minimal inhibitory concentration (MIC) was evaluated with fungal radial growth with thymol or carvacrol concentrations (0-1600mg/l). Mixtures were evaluated using concentrations below MIC values. Radial growth curves were described by the modified Gompertz equation. MIC values of carvacrol were 200mg/l for both fungi. Meanwhile, MIC values of thymol were between 500 and 400mg/l for F verticillioides and R. stolonifer, respectively. A synergistic effect below MIC concentrations for carvacrol (100mg/l) and thymol (100-375 mg/l) was observed. Significant differences (p <0.05) between the Gompertz parameters for the antimicrobial concentrations and their tested mixtures established an inverse relationship between antimicrobial concentration and mycelial development of both fungi. Modified Gompertz parameters can be useful to determine fungistatic concentrations.

El objetivo de este trabajo fue evaluar la actividad antifúngica in vitro del timol y del carvacrol, solos o en mezclas, contra Fusarium verticillioides y Rhizopus stolonifer, y obtener modelos primarios de crecimiento. Se evaluó la concentración inhibitoria mínima (CIM) con el crecimiento radial, se ensayaron concentraciones de timol y carvacrol de 0 a 1.600 mg/l. Las mezclas se evaluaron utilizando concentraciones por debajo de los valores de CIM. Las curvas de crecimiento radial fueron descritas por la ecuación de Gompertz modificada. Se obtuvieron los siguientes valores de CIM: carvacrol, 200 mg/l para las 2 especies; timol, 500 mg/l y 400 mg/l para F. verticillioides y R. stolonifer, respectivamente. Se observó un efecto sinèrgico a concentraciones inferiores a las CIM para el carvacrol (100mg/l) y el timol (100-375 mg/l). Hubo diferencias significativas (p <0,05) entre los parámetros de crecimiento de Gompertz; se estableció que existe una relación inversa entre la concentración de los antimicrobianos y el desarrollo del micelio de ambos hongos.

Estimation of growth in solid state fermentation: A review

@#Carleysmith and Fox (1984) stated “without doubt, the single most vital yet most problematical value sought duringfermentation is biomass estimation”. Achieving a positive result in determining biomass remains a major challenge insolid state fermentation (SSF). Fungi are well-characterised microorganisms and are widely used in SSF due to theirability to colonise and penetrate into the solid substrate. The compressed structure of the mycelia and the solid substratedoes not allow a complete recovery of the biomass, which may not be insurmountable. Since the use of a directtechnique such as the dry weight method is impractical, the use of an indirect estimation technique is the only alternative.This review examines strategies that have been used to estimate biomass in SSF. Many promising indirect estimationtechniques are available, which can be classified into six categories as follows; (i) measuring cell components notpresent in the substrate; (ii) measuring biomass component present in both substrate and biomass; (iii) measuring othersecondary metabolites; (iv) measuring metabolic activity; (v) measuring images from direct microscopic observation and(vi) measuring biomass from the substrate matrix. New potential technique and future directions are also discussed inthis review. Although significant advances have been made with the availability of various techniques; however, progresshas been very unsatisfactory. The evaluation of microbial growth in SSF may sometimes become laborious, impracticaland inaccurate. Essentially, this remains another critical issue for monitoring growth. The information of the profile offungal biomass growth throughout any SSF process constitutes an essential parameter in estimation of kinetic variablesand subsequently, scale-up of the process.

Tolerance to Polycyclic Aromatic Hydrocarbons (PAHs) by filamentous fungi isolated from contaminated sediment in the Amazon region / Tolerância a Hidrocarbonetos Policíclicos Aromáticos (HPAs) por fungos filamentosos isolados de sedimentos contaminados da região Amazônica

Tolerance to Polycyclic Hydrocarbons Aromatic (PAHs) is considered an important characteristic when assessing the bioremediation potential of microorganisms. Given this, the objective of this research was to assay filamentous fungi from the Amazon region, isolated from sediments with differents levels of contamination by PAHs, for tolerance to phenanthrene and pyrene. To achieve this, fungal cultures plugs (5 mm), obtained after 7 days growth, were transferred to petri dishes containing 20% Sabouraud dextrose agar medium, after surface innoculation with phenanthrene and pyrene crystals, separately. Radial mycelial growth was evaluated after 10 days at five different concentration levels for each contaminant and control group, all in triplicate for each treatment. Fungal growth and growth inhibition rates were calculated. The average growth of the colonies in each treatment was compared with one-way ANOVA, followed by a Tukey Test (p < 0,05). All fungi showed tolerant to phenanthrene and pyrene. However, Hypoxylon sp. showed the lowest growth inhibition rate and average growth rates significantly different of the other six tested species. Hypoxylon sp. has been shown to be a promising genetic resource for use in new studies of PAHs degradation.

A tolerância a Hidrocarbonetos Policíclicos Aromática (HPAs) é considerada como uma característica importante na avaliação do potencial de micro-organismos para biorremediação. Diante disso, o objetivo desta pesquisa foi avaliar fungos filamentosos da região amazônica, isolados de sedimentos com diferentes níveis de contaminação por HPAs, quanto à tolerância ao fenantreno e pireno. Para tanto, discos das culturas fúngicas (5 mm), obtidas após 7 dias de crescimento, foram transferidas para placas de Petri contendo meio Agar Sabouraud Dextrose a 20%, após inoculação superficial com cristais de fenantreno e pireno, separadamente. O crescimento micelial radial foi avaliado após 10 dias em cinco concentrações diferentes para cada contaminante e grupo controle, ambos em triplicata para cada tratamento. As taxas de crescimento fúngico e de inibição de crescimento foram calculadas. O crescimento médio das colônias em cada tratamento foi comparado com ANOVA one way, seguido pelo teste de Tukey (p < 0,05). Todos os fungos mostraram tolerância ao fenantreno e ao pireno. No entanto, Hypoxylon sp. apresentou menor taxa de inibição de crescimento e taxas médias de crescimento significativamente diferentes das outras seis espécies testadas. Hypoxylon sp. tem se mostrado um recurso genético promissor para uso em novos estudos sobre degradação de HPAs.

The use of chitosan in protecting wooden artifacts from damage by mold fungi

Background: Many buildings in Egypt e.g. museums, mosques and churches, do not possess controlled environments for minimizing the risks of damage of wooden artifacts due to the growth of fungi. Fungal damage usually appears as change in wood color, appearance of stains, and sometimes deformation of wooden surfaces. In this study we focused on the effect that some fungi exert on the properties of wooden artifacts and evaluated the effectiveness of different concentrations of chitosan on their protection against damage by mold fungi. Results: Samples were collected from different monuments and environments, and fungi growing on them were isolated and identified. The isolated Penicillium chrysogenum, Aspergillus flavus and /Aspergillus niger strains were used for the infestation of new pitch pine samples. The results revealed that the lightness of samples infected with any of the tested fungi decreased with increasing incubation times. XRD analysis showed that the crystallinity of incubated samples treated individually with the different concentrations of chitosan was lower than the crystallinity of infected samples. The crystallinity index measured by the first and the second method decreased after the first and second months but increased after the third and fourth months. This may due to the reducing of amorphous part by enzymes or acids produced by fungi in wooden samples. Conclusions: The growth of fungi on the treated wood samples decreased with increasing the concentration of chitosan. Hence, it was demonstrated that chitosan prevented fungal growth, and its use could be recommended for the protection of archeological wooden artifacts.

Efectos de la temperatura, la actividad de agua y el tiempo de incubación en el crecimiento fúngico y la producción de aflatoxina B1 por aislados toxicogénicos de Aspergillus flavus en sorgo / Effects of temperature, water activity and incubation time on fungal growth and aflatoxin B1 production by toxinogenic Aspergillus flavus isolates on sorghum seeds

Sorghum, which is consumed in Tunisia as human food, suffers from severe colonization by several toxigenic fungi and contamination by mycotoxins. The Tunisian climate is characterized by high temperature and humidity that stimulates mold proliferation and mycotoxin accumulation in foodstuffs. This study investigated the effects of temperature (15, 25 and 37 °C), water activity (a w, between 0.85 and 0.99) and incubation time (7, 14, 21 and 28 d) on fungal growth and aflatoxin B1 (AFB1) production by three Aspergillus flavus isolates (8, 10 and 14) inoculated on sorghum grains. The Baranyi model was applied to identify the limits of growth and mycotoxin production. Maximum diameter growth rates were observed at 0.99 a w at 37 °C for two of the isolates. The minimum a w needed for mycelial growth was 0.91 at 25 and 37 °C. At 15 °C, only isolate 8 grew at 0.99 a w. Aflatoxin B1 accumulation could be avoided by storing sorghum at low water activity levels (≤0.91 a w). Aflatoxin production was not observed at 15 °C. This is the first work on the effects of water activity and temperature on A. flavus growth and AFB1 production by A. flavus isolates on sorghum grains.

El sorgo, que se consume en Túnez como alimento humano, puede sufrir la colonización severa de varios hongos toxicogénicos, con la consiguiente bioacumulación de micotoxinas. Además, el clima de Túnez, caracterizado por las altas temperaturas y humedad, estimula el crecimiento fúngico y la acumulación de micotoxinas en los productos alimenticios. Este estudio investigó los efectos de la temperatura (15, 25 y 37 °C), la actividad de agua (a w) (entre 0,85 y 0,99) y el tiempo de incubación (7, 14, 21 y 28 días) sobre el crecimiento y la producción de aflatoxina B1 (AFB1) de 3 aislados de Aspergillus flavus (designados como 8, 10 y 14) que se inocularon sobre granos de sorgo. El modelo Baranyi se aplicó para identificar los límites del crecimiento y la producción de micotoxinas. Las tasas máximas de crecimiento para 2 de los aislados se observaron en la combinación 0,99 a w y 37 °C. La a w mínima necesaria para el crecimiento del micelio fue de 0,91 a 25 °C y 37 °C. A 15 °C, solo el aislado 8 creció a 0,99 a w, pero fue incapaz de producir la aflatoxina B1. Es posible evitar la acumulación de aflatoxina B1 en el sorgo almacenándolo a baja actividad de agua (≤ 0,91 a w). Este es el primer trabajo que ha estudiado el efecto de la actividad del agua y la temperatura sobre el crecimiento de aislados de A. flavus y su producción de aflatoxina B1 en granos de sorgo.

Aflatoxin contamination in stored rice variety PAU 201 collected from Punjab, India.

Background & objectives: The present study was carried out on stored rice variety PAU 201 in Punjab that was not permitted for milling and public distribution due to the presence of damaged grains at levels exceeding the regulatory limits of 4.75 per cent. The aim of the study was to determine fungal and aflatoxin contamination in the rice samples to assess hazard from the presence of damaged grains. Presence of iron in discoloured rice grains was also assessed. Methods: Stored samples of paddy of PAU 201 rice variety were collected from six districts of Punjab, milled and analysed for presence of fungal and aflatoxin contamination. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and Prussian blue staining was used to determine fungal spores and presence of iron, respectively. Results: Aflatoxin analysis of rice samples indicated that none exceeded the Food Safety and Standards (Contaminants, Toxins and Residues) Regulations, 2011 tolerance limit of 30 μg/kg and majority of the samples had levels <15 μg/kg. The proportion of damaged grains exceeding the limit of 5 per cent was observed in 85.7 per cent of the samples. SEM and Prussian blue staining and EDX analysis of black tipped and pin point damaged rice grains did not show presence of fungal structures and presence of iron. Interpretation & conclusions: The results of the study indicated that the stored rice samples did not pose any health concern with respect to aflatoxin contamination as per the criteria laid down by the Food Safety and Standards Authority of India.

Extracellular amylase production of a thermotolerant Fusarium sp: isolated from Eastern Nigerian soil

In this work, an α- amylase producing Fusarium sp. was isolated from the soil at 50 0C. Growth and enzyme production occurred at 30, 45 and 55 ºC. Soybean meal at 1 percent concentration, supplemented with 0.2 percent NH4Cl and 2.5 percent corn starch elicited the highest amylase yield. Optimum pH for the enzyme was pH 6.5 which retained over 60 percent of its activity after 24 h incubation at the pH range of 4.5-7.0. The enzyme showed high activity from 40-70 0C with optimal activity at 50 ºC and 78 percent activity was retained after incubation at 70 ºC for 30min. Catalytic function of the crude amylase was stimulated by Mg (136 percent), Ca (118 percent) and Zn (118 percent) at 2mM concentrations. The enzyme hydrolyzed cassava, potato and yam starches effectively.

Avaliação do efeito do óleo de melaleuca sobre o crescimento micelial in vitro de fungos fitopatogênicos / Evaluation of the effect of melaleuca oil on mycelial growth of phytopathogenic fungi in vitro

A exploração da atividade biológica de compostos secundários presentes no extrato bruto ou óleos essenciais de plantas pode constituir, em uma forma efetiva de controle de doenças em plantas cultivadas. Assim, o objetivo do presente trabalho foi avaliar o efeito do óleo essencial de Melaleuca alternifolia na inibição do crescimento micelial "in vitro" de fungos fitopatogênicos. Os fungos fitopatogênicos testados foram: Macrophomina phaseolina, Sclerotinia sclerotiorum e Alternaria alternata. As concentrações do óleo adicionadas ao meio de cultura foram: 0,0, 0,2, 0,4, 0,6 e 0,8%. A avaliação consistiu em medições do diâmetro das colônias. O óleo essencial de melaleuca inibiu o desenvolvimento dos fungos fitopatogênicos testados podendo representar uma alternativa econômica e ecologicamente viável de controle de doenças de plantas.

The exploration of the biological activity of secondary compounds present in crude extracts or essential oils of plants can in an effective way to control diseases in crops. The objective of this study was to evaluate the effect of essential oil of Melaleuca alternifolia on the inhibition of mycelial growth in vitro of pathogenic fungi. The pathogenic fungi were tested: Macrophomina phaseolina, Sclerotinia sclerotiorum and Alternaria alternata. The concentrations of oil added to the culture medium were 0,0, 0,2, 0,4, 0,6 and 0,8%. The evaluation consisted of measurements of the diameter of the colonies. The essential oil of melaleuca inhibited the development of pathogenic fungi tested could represent an economical and environmentally viable alternative to control plant diseases

Biological Characterization of Marssonina coronaria Associated with Apple Blotch Disease

Marssonina coronaria associated with apple blotch disease causes severe premature defoliation, and is widely distributed in Korea. Thirteen isolates were collected from orchards located in Gyeongbuk Province from 2005~2007. All isolates displayed over 99.6% and 99.2% sequence similarity to each other in internal transcribed spacer regions and partial sequences of 28S rDNA, respectively. The isolates were phylogenetically closely related to Chinese isolates. Selected isolates did not differ in their pathogenicity. The optimum conditions for fungal growth were 20degrees C and pH 6 on peptone potato dextrose agar (PPDA). Peptone and mannose were the best nitrogen and carbon source, respectively. Fungal growth was better on PPDA than on common potato dextrose agar. This study provides valuable information for integrated disease management program and facilitates the routine culturing of M. coronaria.

Plant Hormones Promote Growth in Lichen-Forming Fungi

The effect of plant hormones on the growth of lichen-forming fungi (LFF) was evaluated. The use of 2,3,5-triiodobenzoic acid and indole-3-butyric acid resulted in a 99% and 57% increase in dry weight of the lichen-forming fungus Nephromopsis ornata. The results suggest that some plant hormones can be used as inducers or stimulators of LFF growth for large-scale culture.

A simplified model for A. Niger FS3 growth during phytase formation in solid State fermentation

A simplified model to describe fungal growth during citric pulp fermentation for phytase production was described for the first time. Experimental data for biomass growth were adjusted to classical mathematical growth models (Monod and Logistic). The Monod model predictions showed good agreement with the experimental results for biomass concentration during 96 hours of fermentation. Parameters such as yield of biomass from oxygen (Y X/O), maintenance coefficient (m) and specific growth rate (µ) were compared showing a good correlation between the data and the model. An alternative method for biomass determination in this process was developed since a great correlation was found between biomass growth and enzyme formation.

Um modelo simplificado para descrever o crescimento fúngico durante a fermentação em polpa citric para a produção da fitase foi descrita pela primeira vez. Dados experimentais para a formação de biomassa foram ajustados a modelos clássicos de crescimento microbiano (Monod e Logístico). O modelo Monod previsto mostrou boa correlação aos resultados experimentais para a concentração de biomassa até 96 horas de fermentação. Parâmetros como rendimento de biomassa a partir de oxigênio (Y X/O), coeficiente de manutenção (m) e taxa específica de crescimento (µ) foram comparados mostrando uma boa correlação entre os dados e o modelo. Um método alternativo para a determinação de biomassa neste processo foi desenvolvido a partir de uma excelente correlação encontrado entre o crescimento microbiano e a formação da enzima.

Effect of Ribitol and Plant Hormones on Aposymbiotical Growth of the Lichen-forming Fungi of Ramalina farinacea and Ramalina fastigiata

This study was aimed at evaluating the growth promoting effect of symbiotic algal polyol (ribitol) and plant hormones on the lichen-forming fungi (LFF), Ramalina farinacea (CH050010 and 40403) and Ramalina fastigiata. The addition of ribitol to basal (malt-yeast extract) medium enhanced the relative growth rates of all three LFF. R. farinacea (CH050010), R. farinacea (40403) and R. fastigiata (H06127) showed 35.3%, 29.0% and 29.3% higher growth rates, respectively, compared to the control. IBA (indole-3-butyric acid) and TIBA (2,3,5-tridobenzoic acid) also increased growth rates of the LFF by 34 to 64% and 7 to 28%, respectively, compared to the control. The combination of ribitol with IBA or TIBA synergistically increased the growth of all LFF. For example, ribitol and IBA treatments increased growth rates of R. farinacea (CH050010), R. farinacea (40403) and R. fastigiata (H06127) by 79.4%, 40.3% and 72.8% in, respectively, compared to those grown on the basal medium. The stimulating effect of ribitol and IBA on the LFF growth induced vertical development of the fungal mass in culture. We suggest that lichen-forming fungal growth of Ramalina lichens can be stimulated aposymbiotically by supplementing polyols and plant hormones to the basal medium in the mass production of lichen secondary metabolites under large scale culture conditions.