0000000000190158
AUTHOR
Maurice Bensoussan
Distributions of the growth rate of the germ tubes and germination time of Penicillium chrysogenum conidia depend on water activity
The effects of water activities for sporulation (a(wsp)) and germination (a(wge)) on the distributions of the growth rate of the germ tubes (mu) and the germination time (t(G)) of Penicillium chrysogenum conidia were determined by monitoring the length of the same germ tubes throughout the experiments automatically. No relationship between the individual t(G)'s and mu's could be established. Irrespective of the water activity for germination, mu was greater and t(G) was less for conidia produced at 0.95a(wsp) than that at 0.99a(wsp). At 0.99 a(wge) the mean and the standard deviation of t(G) were smaller than those obtained at 0.95a(wge). At 0.99a(wge), normal distributions for mu and t(G) …
Modes d’invasion et d’expression de Botrytis cinerea, champignon pathogène de la Vigne
Introduction : Le champignon phytopathogene Botrytis cinerea est un polyphage qui cause d'enormes degâts en agriculture. La culture de la vigne represente en France des enjeux economiques importants. La vigne est touchee par la maladie de la pourriture grise due a B. cinerea, conduisant a des pertes de rendement importantes. L'objectif de cette etude est, compte tenu des effets sur le developpement fongique de facteurs environnementaux (Sautour et al., 2001a, b), la caracterisation du caractere pathogene et la comparaison des structures de populations de B. cinerea isolees de differentes regions de France : Bourgogne, Languedoc et Champagne. Materiel et methodes : Les suspensions de conidie…
A temperature-type model for describing the relationship between fungal growth and water activity
Growth of Penicillium chrysogenum, Aspergillus flavus, Cladosporium cladosporioides and Alternaria alternata at their respective optimum temperatures was studied in Potato Dextrose Agar (PDA) medium at different water activities (a(w)) adjusted with glycerol. The growth rate (mu) was expressed as the increase in colony radius per unit of time. This paper extends the model that showed the relationship between temperature and bacterial growth rate developed by Rosso et al. [J. Theor. Biol. 162 (1993) 447] to describe the influence of a(w) on fungal development. An excellent correlation between the experimental data and the model predictions was obtained, the regression coefficients (r2) were …
Inactivation of conidia of Penicillium chrysogenum, P. digitatum and P. italicum by ethanol solutions and vapours
A fractional factorial design, 2(5-1) experiments, was used for assessing the influence of 5 factors: water activity, aw [0.7, 0.9], temperature, T ( degrees C) [10, 30], mode of application, A [liquid, vapour], ethanol concentration, E (% w/w) [5, 10] and time, t (d) [1, 4] on the inactivation of spores of Penicillium chrysogenum, P. digitatum and P. italicum. Survival was determined by germination at optimal conditions within 3d. The experimental response was log (N 0/Nt), where N 0 and Nt (spore ml(-1)) the concentrations of viable spores at t=0 and t respectively. By a decreasing order of sensitivity to ethanol, moulds were ranked as followed: P. digitatum, P. italicum and P. chrysogenu…
Production of 6-pentyl-?-pyrone byTrichoderma harzianum from 18?n fatty acid methyl esters
Biosynthesis of 6-pentyl-α-pyrone byTrichoderma harzianum in two different media was evaluated. Best yields were found in nitrogen deficient medium (C/N=60). Limited growth seems to favour the production of this lactone. When fungal cells, precultured in low nitrogen medium, were incubated on methyl ricinoleate (10 g/l, C/N=60) an increase in 6-pentyl-α-pyrone production was observed in comparison with the media containing methyl oleate or methyl linoleate.
Factors affecting physiology of mycelial growth and mushrooms aroma production in solid state fermentation
L'effet de différentes sources d'azote et du rapport C/N sur la croissance mycélienne et sur l'intensité aromatique dégagée par trois espèces du genre #Morchella$ et d'une espèce du genre #Pleurotus$ a été étudié sur agar puis sur support solide. Les résultats ont été à la base du choix du nitrate de sodium comme source d'azote, du rapport C/N de 10 ainsi que du mycélium de #M. esculenta$ come source potentielle pour la production de l'arôme de morille. L'identification des molécules contribuant à l'arôme réalisée par CPG-SM a révélé de larges différences entre #M. esculenta$ et #P. cornucopiae$. Dans la mesure où l'arôme produit par le mycélium rappelle celui du carpophore, ce résultat con…
Pleurotus ostreatus volatile aroma compounds identified from fruit-body and from mycelium grown in submerged and solid-state cultures
Comparative analyses of volatile aroma compounds of the Pleurotus ostreatus JMO.95 fruit-body and its corresponding mycelium grown in liquid, on agar surface, or on solid support cultures have been carried out by dynamic headspace concentration using GC/MS and GC/sniffing. The aroma of the fruit-body was due essentially to the presence of octan-3-one and, in a lesser extent, to the presence of octan-3-ol. Other compounds, such as oct-l-en-3-ol, oct-l-en, 2-methylbutanol and a-pinene were also present in low concentrations. The comparison of the aromatic spectra of the fruit-body with the aromatic spectra of mycelia obtained under different culture conditions indicated that the main aromatic…
Lag time for germination of Penicillium chrysogenum conidia is induced by temperature shifts.
In the environment, fungal conidia are subject to transient conditions. In particular, temperature is varying according to day/night periods. All predictive models for germination assume that fungal spores can adapt instantaneously to changes of temperature. The only study that supports this assumption (Gougouli and Koutsoumanis, 2012, Modelling germination of fungal spores at constant and fluctuating temperature conditions. International Journal of Food Microbiology, 152: 153-161) was carried out on Penicillium expansum and Aspergillus niger conidia that, in most cases, already produced germ tubes. In contrast, the present study focuses on temperature shifts applied during the first stages…
Effect of inoculum size and water activity on the time to visible growth of Penicillium chrysogenum colony.
In order to assess the effect of the inoculum size on the time to visible growth for Penicillium chrysogenum, the correlation described by Gonzalez et al. (Gonzalez, H.H.L., Resnik, S.L., Vaamonde, G., 1987. Influence of inoculum size on growth rate and lag phase of fungi isolate from Argentine corn. International Journal of Food Microbiology 4, 111-117) was compared to the model introduced by Gougouli et al. (Gougouli, M., Kalantzi, K., Beletsiotis, E., Koutsoumanis, K.P., 2011. Development and application of predictive models for fungal growth as tools to improve quality control in yogurt production. Food Microbiology 28, 1453-1462). Based on the regression coefficient, the latter model p…
Modelling the effect of ethanol on growth rate of food spoilage moulds
The effect of ethanol (E) on the radial growth rate (mu) of food spoilage moulds (Aspergillus candidus, Aspergillus flavus, Aspergillus niger, Cladosporium cladosporioides, Eurotium herbariorum, Mucor circinelloides, Mucor racemosus, Paecilomyces variotii, Penicillium chrysogenum, Penicillium digitatum, Rhizopus oryzae and Trichoderma harzianum) was assessed in Potato Dextrose Agar (PDA) medium at a(w) 0.99, 25 degrees C. In order to model this effect, the Monod type equation described previously by Houtsma et al. (Houtsma, P.C., Kusters, B.J.M., de Wit, J.C., Rombouts, F.M., Zwietering, M.H., 1994. Modelling growth rates of Listeria monocytogenes as a function of lactate concentration. Int…
Modeling the effect of ethanol vapor on the germination time of Penicillium chrysogenum.
The influence of ethanol vapor on germination of Penicillium chrysogenum was determined on yeast nitrogen base plus glucose agar medium at 25 degrees C. Ethanol vapors were generated by 0 to 6% (wt/wt) ethanol solutions at the bottom of hermetically closed petri dishes. The logistic equation was used to describe the data as the percentage of germination versus time and to estimate the germination time. The effect of ethanol concentration on germination time was described by a new reparameterized equation, resulting in an estimated limiting ethanol concentration of 4.3%. Up to 3% ethanol, all spores germinated, and the germination time increased with increasing ethanol concentration. At 3.5 …
Validation of a predictive model for the growth of Botrytis cinerea and Penicillium expansum on grape berries.
The objective of this study was to develop and to validate a model for predicting the combined effect of temperature and a(w) on the radial growth rate, mu, of Botrytis cinerea and Penicillium expansum on grape berries. The proposed strategy was based on the gamma-concept developed previously [Zwietering, M.H., Wijtzes, T., de Wit, J.C., van't Riet, K. 1992. A decision support system for prediction of the microbial spoilage in foods. Journal of Food Protection. 12, 973-979]: mu=mu(opt).gamma(T).gamma(a(w)), where the gamma functions were cardinal models with inflection (CMI), mu(opt) the radial growth rate on grape berries. Firstly, the cardinal temperatures and a(w)'s were estimated indepe…
Use of the Weibull model to describe inactivation of dry harvested conidia of different Penicillium species by ethanol vapours
Aims: This study aimed at modelling the effect of ethanol vapours, in the range 0·7–7·5 kPa, on the inactivation of dry-harvested conidia of Penicillium chrysogenum, Penicillium digitatum and Penicillium italicum. Methods and Results: Survival curves were modelled by a Weibull model: log (N/N0) = −1/2·303 (t/α)β. The shape parameter β was different from one in all cases, indicating that the classical first-order kinetics approach is the exception rather than the rule. Survival curves exhibited upward concavity (β < 1) with the notable exception of P. chrysogenum at ethanol vapour pressures 0·7 and 1·5 kPa. The scale parameter α (h) varied greatly depending on the ethanol vapour pressure a…
Quantitative separation of Trichoderma lipid classes on a bonded phase column.
Bond Elut aminopropyl columns were used to purify the different lipid classes of Trichoderma harzianum and Trichoderma viride. This methodology permitted good separation of the fungal lipid classes in less time than traditional techniques. The incorporation of [1 (14)C]linoleic acid into neutral lipids, free fatty acids and phospholipids was quantified for both strains. The fatty acid profile of the different lipid classes of these fungal strains was determined as a function of culture time.
Standardisation of methods for assessing mould germination: a workshop report.
International audience; The first workshop on predictive mycology was held in Marseille, France, 2–4 February 2005 under the auspices of the French Microbiological Society. The purpose of the workshop was to list the different techniques and definitions used by scientists for assessing mould germination and to evaluate the influence of the different techniques on the experimental results. Recommendations were made when a large consensus was obtained. In order to facilitate the study of germination, alternative methods to microscopic examination were examined.
Effect of storage conditions (relative humidity, duration, and temperature) on the germination time of Aspergillus carbonarius and Penicillium chrysogenum.
Fungal conidia are disseminated, often in the air, for a certain period of time, prior to contaminating food products. The objective of this study was to examine the effects of the relative humidity, RH (%), time (day), and temperature (°C) during this period of time, called "storage", on the germination time, τ (h), of Aspergillus carbonarius and Penicillium chrysogenum. A Doehlert design was used in the range, 20-100% RH, 2-28 days, and 5-25 °C. As compared to un-stored conidia, the germination time of conidia stored at 60% RH, 15 days, 5 °C was increased by 23 and 28%, for A. carbonarius and P. chrysogenum, respectively. Stored conidia exhibited a minimum τ value at 60% RH, and 100% RH f…
Modelling the effect of temperature, pH, water activity, and organic acids on the germination time of Penicillium camemberti and Penicillium roqueforti conidia.
International audience; In this study, the influence of environmental factors on the germination time of Penicillium camemberti and Penicillium roqueforti conidia was evaluated. To do so, the effects of i/temperature, pH, water activity, and ii/organic acids were determined using models based on i/cardinal values, and ii/minimum inhibitory concentration (MIC) respectively. Cardinal values for germination of conidia were not observed to be species dependent. Minimum temperatures were estimated to be below the freezing point, with an optimum of 26.9 degrees C, and a maximum of 33.5 degrees C. For both species, minimal and optimal a(w) values were found to be 0.83 and 0.99, respectively, while…
Production of volatile compounds in model milk and cheese media by eight strains of Geotrichum candidum Link
SummaryEight strains of Geotrichum candidum isolated from cheese were compared for aroma production. Twenty-four components, including alcohols, methyl ketones, fatty acids and esters, were identified by gas–liquid chromatography and gas chromatography–mass spectrometry of the volatile compounds produced by G. candidum cultures. Strains could be differentiated by their ability to produce dimethyldisulphide, phenol, phenylethanol and methyl ketones.
The logarithmic transformation should be avoided for stabilising the variance of mould growth rate.
Abstract Radial growth rate, μ (mm d − 1 ) was evaluated by plotting the radius of the colony, r (mm) versus time (d) for Alternaria alternata , Aspergillus flavus , Cladosporium cladosporioides , Mucor racemosus , Rhizopus oryzae and Trichoderma harzianum at different T and a w . For each of the 12 data sets, an analysis of variance of the raw growth rate data was performed. It was observed from the P -values that all square-root transformed values of μ were non-significant at the significance level α = 0.05, whereas for untransformed values of μ , three of the 12 values were significant and for logarithmically transformed μ , nine of the 12 values were significant at the significance lev…
Prediction of conidial germination of Penicillium chrysogenum as influenced by temperature, water activity and pH.
M. SAUTOUR, A. ROUGET, P. DANTIGNY, C. DIVIES AND M. BENSOUSSAN. 2001 Aims: Conidial germination of Penicillium chrysogenum was carried out under operating conditions compatible with a pastries manufacturing process. Methods and Results: A range, limited by two experimental values, was defined for each environmental factor tested: temperature (15 or 25°C), water activity (0·75 or 0·85) and pH (3·5 or 5·5). A closed device was made, which maintained an equilibrium between water activity of the culture medium and atmospheric relative humidity during 25 days, to follow spore germination. The combined effects of temperature, water activity and pH on spore germination were studied by applying fa…
Metabolism of Linoleic Acid or Mevalonate and 6-Pentyl-α-Pyrone Biosynthesis by Trichoderma Species
The understanding of the biosynthetic pathway of 6-pentyl-α-pyrone in Trichoderma species was achieved by using labelled linoleic acid or mevalonate as a tracer. Incubation of growing cultures of Trichoderma harzianum and T. viride with [U- 14 C]linoleic acid or [5- 14 C]sodium mevalonate revealed that both fungal strains were able to incorporate these labelled compounds (50 and 15%, respectively). Most intracellular radioactivity was found in the neutral lipid fraction. At the initial time of incubation, the radioactivity from [ 14 C]linoleic acid was incorporated into 6-pentyl-α-pyrone more rapidly than that from [ 14 C]mevalonate. No radioactivity incorporation was detected in 6-pentyl-…
Validation of a predictive model for the growth of chalk yeasts on bread.
The present study focused on the effects of temperature, T, and water activity, aw, on the growth of Hyphopichia burtonii, Pichia anomala, and Saccharomycopsis fibuligera on Sabouraud Agar Medium. Cardinal values were estimated by means of cardinal models with inflection. All the yeasts were xerophilic, and they exhibited growth at 0.85 aw. The combined effects of T, aw, and pH on the growth of these species were described by the gamma-concept and validated on bread in the range of 15-25 °C, 0.91-0.97 aw, and pH 4.6-6.8. The optimum growth rates on bread were 2.88, 0.259, and 1.06 mm/day for H. burtonii, P. anomala, and S. fibuligera, respectively. The optimal growth rate of S. fibuligera o…
A model for the effect of pH on the growth of chalk yeasts.
Hyphopichia burtonii, Pichia anomala, and Saccharomycopsis fibuligera were isolated from spoiled packaged sliced bread. These chalk yeasts were characterized by a wide range of pH for which growth was almost optimum. Thus, the curve growth vs pH exhibited plateau and sharp profiles close to the minimum and the maximum pH. This study described a chalk yeast model (CYM) for the effect of pH derived from a new germination model for fungi (Dantigny, P., Nanguy, S., P.-M., Judet-Correia, D., and Bensoussan, M. 2011, International Journal of Food Microbiology, 146, 176-181). The CYM is asymmetric, versatile, based on parameters with biological significance, and compatible with the gamma concept. …
Basis of predictive mycology.
Abstract For over 20 years, predictive microbiology focused on food-pathogenic bacteria. Few studies concerned modelling fungal development. On one hand, most of food mycologists are not familiar with modelling techniques; on the other hand, people involved in modelling are developing tools dedicated to bacteria. Therefore, there is a tendency to extend the use of models that were developed for bacteria to moulds. However, some mould specificities should be taken into account. The use of specific models for predicting germination and growth of fungi was advocated previously [ Dantigny, P., Guilmart, A., Bensoussan, M., 2003. Basis of predictive mycology. In Proceedings of the 4th Internatio…
Grape pulp, grape pips and their mixture: Novel substrates or supports for solid state fermentation
Grape marc, comprising of grape pulp and grape pips, is generated in high quantities during ethanol production, but has no significant commercial value. The components of the grape marc, individually or in combination, can serve as substrate or support in solid state fermentation. The potential benefits of sieved fractions (800-3150 µm particle size) was, therefore, evaluated using Trichoderma viride, with or whithout enrichment. Based on sorption isotherm profiles, grape pulp showed the best performance, though its ability to promote biomass formation was the lowest. The latter could be improved by enrichment with glucose. It, thus, offers potential as a reusable support. Grape pips promot…
Action de la chlorhexidine sur l'expression de la virulence de
Abstract Candida albicans is an opportunistic yeast. Its pathogenicity is linked to the susceptibility of the host surface as well as to particular factors of the strain: adhesion, filamentous growth and secretion of proteolytic enzymes. Chlorhexidine digluconate is an antiseptic with fungicidal properties. The action of the antiseptic on the growth of the yeast shows a minimal inhibitory concentration (MIC) at 50 μg·mL−1 and a minimal fungicidal concentration (MFC) at 100 μg·mL−1. The consequences of antiseptic treatment are studied using two indicators of pathogenicity: filamentation and the secretion of acid proteinase. Concerning the morphological indicator, a complete inhibition of fil…
Impact of water activity of diverse media on spore germination of Aspergillus and Penicillium species
International audience; The effects of water activity (aw) of diverse media i/ culture medium for sporogenesis, aw sp ii/ liquid spore suspension medium, aw su and iii/ medium for germination, aw ge, on the germination time tG of Aspergillus carbonarius, Aspergillus flavus, Penicillium chrysogenum and Penicillium expansum were assessed according to a screening matrix at 0.95 and 0.99 aw. It was shown that i/ reduced tGs were obtained at 0.95 aw sp except for P. expansum ii/ a significant effect of aw su on tG was demonstrated for A. carbonarius, P. chrysogenum and P. expansum iii/ the most important factor for controlling the germination time was the medium for germination except for A. car…
Modelling the inhibitory effect of copper sulfate on the growth of Penicillium expansum and Botrytis cinerea
Aims: This study aimed to investigate the effect of copper sulfate (from 0 to 8 mmol kg−1) on radial growth rate and lag time of two moulds responsible for vine grapes spoilage: Penicillium expansum strain 25·03 and Botrytis cinerea, strains BC1 and BC2. Methods and results: A new model was developed to describe tailing and shoulders in the inhibition curves. Because of tailing, the minimum inhibitory concentration (MIC), was not defined as the concentration at which no growth was observed, but as the concentration at which the lag time was infinite. The concentrations at which μ = μopt/2, (Cu50), were in the range of 2·2–2·6 mmol kg−1. Radial growth rate of P. expansum and the reciprocal…
Lipid accumulation inTrichodermaspecies
Two filamentous fungi, Trichoderma harzianum and Trichoderma viride, were compared for their ability to synthesize lipids on different carbon and nitrogen sources. Three culture media were selected for each strain after preliminary screening. All the test media were nitrogen-deficient (C/N = 60) so as to stimulate lipid accumulation. For both microorganisms the glucose-ammonium sulphate medium was the most conducive to lipid production: a lipid accumulation of 17% (w/w) of biomass dry weight was obtained for T. harzianum and of 32% (w/w) of biomass dry weight for T. viride. In sucrose-sodium nitrate medium T. harzianum was able to accumulate almost 25% (w/w) of its biomass in lipid form. Ho…
A new model for germination of fungi.
Abstract The objective of this study was to design a germination model dedicated to fungi. The percentage of germinated spores, P(%), depended on the maximum percentage of germination P max (%), the germination time, τ (h) and a design parameter, d (-) according to : P = P max 1 − 1 1 + t τ d . The model was capable to fit satisfactorily either apparent symmetric and asymmetric shapes of germination curves. The accuracy of τ determined by using the logistic or the present model was at least twice that obtained by the Gompertz equation. In contrast to the logistic model, the new model is by essence asymmetric. Therefore, its use is consistent with skewed distributions of the individual germi…
A simple protocol for extraction and detection of pyrazines produced by fungi in solid state fermentation
A protocol for the extraction and detection of pyrazines produced by fungi in Solid State Fermentation that gave good recovery of these compounds was devised together with specific techniques for detection by Gas Chromatography (GC). The protocol involved solid-liquid and liquid-liquid extractions, concentration of the extracts and GC analysis. Extraction yields were measured from a model system in which synthetic pyrazines were added. Extracts were analysed with a gas chromatograph equipped with a thermo-ionic detector to allow specific pyrazine detection.