Growth Of Geotrichum Candidum Research Articles

Effect of temperature on the growth of Geotrichum candidum and chemical control of sour rot on tomatoes

Effect of temperature on the growth of Geotrichum candidum and chemical control of sour rot on tomatoes

Novel application of HKUST-1 metal–organic framework as antifungal: Biological tests and physicochemical characterizations

The HKUST-1 metal–organic framework (MOF) was successfully applied as a biocidal material against representative yeast and mold. The synthesized MOF showed a strong antifungal effect against Saccharomyces cerevisiae for which the growth was completely inhibited, whereas the growth of Geotrichum candidum was reduced from 6.16 to 1.29CFUmL−1. The antifungal action was related to copper ions released into the culture medium due to a progressive degradation of the crystalline structure of the material that involved the formation of surface extra-framework Cu(I). This study shows the potential of using copper-based metal–organic frameworks for a controlled release of biologically active copper ions.

Surface growth of geotrichum candidum: effect of the environmental factors on its dynamics

The growth dynamics of Geotrichum candidum was studied on the surface of the skim milk agar with respect to the temperature, pH and water activity/NaCl content. At pH ranging from 5.0 to 7.0, the fungus growth rates were similar, whereas the temperature and water activity represented by salt addition in concentration of 3 % influenced the growth significantly. The effect of incubation temperature on the surface growth rate was modelled with G-Twmodel. Designed model proved to be good predictor of fungus growth at used environmental conditions. As the filamentous fungus under study is commonly present on the surface of various cheeses, the quantitative data found in this work can provide useful information closely related to real fungus growth, e.g. calculation of time required for G. candidum to reach visible 3 mm colony. The predictions showed that, for example at 0 % NaCl content, such colonies were grown for 52.2, 30.7, 18.4, 14.4, 13.9 hat temperatures of 10, 14, 19, 23, 27 °C, respectively.

Sequential use of ammonium and leucine as nitrogen sources during growth of Geotrichum candidum on a glucose based medium

Sequential use of ammonium and leucine as nitrogen sources during growth of Geotrichum candidum on a glucose based medium

Sequential use of ammonium and leucine as nitrogen sources during growth of Geotrichum candidum on a glucose based medium

Geotrichum candidum growth on ammonium and leucine as nitrogen sources and glucose as a carbon source was examined. A clear preference of G. candidum for ammonium over leucine as a nitrogen source was shown. Indeed, ammonium was completely exhausted at the end of exponential growth after less than 35 hrs of culture; in contrast only 5% of leucine was concomitantly assimilated. Growth continued at slower rates on glucose and leucine as carbon and nitrogen sources respectively, and at the end of culture (185 hrs), leucine was completely exhausted.

Diffusion of lactate and ammonium in relation to growth of Geotrichum candidum at the surface of solid media.

Geotrichum candidum was cultivated at the surface of solid model media containing peptone to simulate the composition of Camembert cheese. The surface growth of G. candidum induced the diffusion of substrates from the core to the rind and the diffusion of produced metabolites from the rind to the core. In the range of pH measured during G. candidum growth, constant diffusion coefficients were found for lactate and ammonium, 0.4 and 0.8 cm(2) day(-1), respectively, determined in sterile culture medium. Growth kinetics are described using the Verlhust model and both lactate consumption and ammonium production are considered as partially linked to growth. The experimental diffusion gradients of lactate and ammonium recorded during G. candidum growth have been fitted. The diffusion/reaction model was found to match with experimental data until the end of growth, except with regard to ammonium concentration gradients in the presence of lactate in the medium. Indeed, G. candidum preferentially assimilated peptone over lactate as a carbon source, resulting in an almost cessation of ammonium release before the end of growth. On peptone, it was found that the proton transfer did not account for the ammonium concentration gradients. Indeed, amino acids, being positively charged, are involved in the proton transfer at the beginning of growth. This effect can be neglected in the presence of lactate within the medium, and the sum of both lactate consumption and ammonium release gradients corresponded well to the proton transfer gradients, confirming that both components are responsible for the pH increase observed during the ripening of soft Camembert cheese.

Growth of Geotrichum candidum and Penicillium camembertii in liquid media in relation with the consumption of carbon and nitrogen sources and the release of ammonia and carbon dioxide

The growth of the filamentous fungi Geotrichum candidum and Penicillium camembertii on peptones as a sole carbon and nitrogen source, and in the presence of a second carbon source, lactic acid, have been compared. On both media, G. candidum exhibited similar kinetics until the end of growth, since it preferentially metabolized peptones as a carbon source, and lactic acid only for cellular maintenance during stationary phase. Growth of G. candidum was then nitrogen limited (peptones). On the contrary, fewer amino acids were convenient carbon sources for P. camembertii, resulting in a simultaneous consumption of peptones and lactic acid, and a cessation of growth due to the complete consumption of lactic acid. Morever, a lower amount of ammonia was produced since this metabolite resulted from the deamination of only carbon and nitrogen source amino acids. The production of ammonia induced an alkalinization of the broth (from 4.5 to 7.1). Morever, it was demonstrated that lactic acid consumption contributed also to media alkalinization (final pH 8.4). In absence of lactic acid, the medium contained a lower amount of available carbon, resulting in the absence of stationary state, deceleration growth phase was immediately followed by the death phase.

Carbon and nitrogen substrates consumption, ammonia release and proton transfer in relation with growth of Geotrichum candidum and Penicillium camemberti on a solid medium

It is difficult to determine fungal biomass growing on a solid medium directly. Therefore, indirect ways of measuring this growth have to be used instead. For this purpose, the kinetics of growth, of substrate consumption and of release of metabolites must be correlated. This has been carried out for Geotrichum candidum and Penicillium camemberti growing on a gelified lactic acid+peptone medium. Peptone was shown to be preferred by G. candidum as a carbon and energy source, in contrast to the behaviour observed for P. camemberti. At the end of growth, G. candidum released about three times more ammonia than P. camemberti. In both cases, the total number of protons consumed during growth was close to the sum of the number of moles of metabolized lactic acid and formed ammonia. During the main part of growth, constant biomass on substrate yields (peptone, lactic acid) was observed for both microorganisms. Therefore, in pure solid cultures, the biomass concentration of both species could be deduced either from ΔpH or from the reduction of substrates. From the above, an estimate of G. candidum biomass in mixed culture could be derived from the determination of ammonia release.

Growth of Geotrichum candidum and Penicillium camemberti Cultivated on Liquid Media Correlated with Ammonia and Methanethiol Emission

Growth of Geotrichum candidum and Penicillium camemberti Cultivated on Liquid Media Correlated with Ammonia and Methanethiol Emission

Growth of Geotrichum candidum and Penicillium camemberti Cultivated on Liquid Media Correlated with Ammonia and Methanethiol Emission

Growth of Geotrichum candidum and Penicillium camemberti Cultivated on Liquid Media Correlated with Ammonia and Methanethiol Emission

Growth ofGeotrichum candidum and Penicillium camemberti Cultivated on Liquid Media Correlated with Ammonia and Methanethiol Emission

The growth of Geotrichum candidum and Penicillium camemberti plays an important role in the ripening of Camembert-type cheeses, but the monitoring of the corresponding kinetics for fungal cocultures on solid media appears difficult. Continuous and non-intrusive methods to characterize the growth of both species (like the monitoring of the emissions of ammonia and volatile sulphur compounds) may be highly relevant, under the condition that such emissions could be correlated with growth. This would be easier to investigate in submerged culture, since total biomass concentration is known to vary in proportion to broth turbidity. For this reason, growth kinetics, ammonia and flavour gas emission of both Geotrichum candidum and Penicillium camemberti grown separately in submerged cultures under the conditions of low aeration rate and uncontrolled pH were continuously recorded. In the basal medium (peptone + lactate supplemented with both glutamic acid and methionine [1 g/l] each), no significant gas emission was observed during the growth of both fungi. Ammonia and sulphur gas emissions by G. candidum were a little stimulated by supplementing the basal medium with trace elements, and, at a larger extent, by the addition of inorganic phosphate: Such a gaseous emission took place at the end of the growth phase of G.candidum. Irrespective of the basal medium supplementation, no significant emission of ammonia and sulphur gas was observed during the growth of P.camemberti. For the media and strains used, ammonia and volatile sulphur compounds emissions unequivocally showed the growth of Geotrichum candidum.

A New Model for the Reconstruction of Biomass History from Carbon Dioxide Emission during Batch Cultivation of Geotrichum candidum.

A non-structured model has been developed to describe the CO2 emission during growth of Geotrichum candidum on a lactate + peptone-based liquid medium. From the nitrogen and carbon mass balances, it was shown that about 50% of the total CO2 released was from the metabolism of the energy supply for biosynthesis, and the remaining from that for maintenance; thus, CO2 production was considered to be partially associated with growth. The model fitted the experimental data as long as a net growth was observed (0-50 h). The coefficients for growth- and non-growth-associated CO2 production were A = 0.646 (dimensionless) and B = 0.017 h(-1), respectively. From the coefficients of the model and the CO2 history data, the biomass kinetics has been reconstructed, and the calculated biomass concentrations agree fairly well with the experimental data. From this, measurement of the CO2 evolved may be used as an indirect and non-intrusive method of monitoring fungal growth during the first 50 h of cultivation.

A new model for the reconstruction of biomass history from carbon dioxide emission during batch cultivation of geotrichum candidum

A nonstructured model has been developed to describe the CO 2 emission during growth of Geotrichum candidum on a lactate + peptone-based liquid medium. From the nitrogen and carbon mass balances, it was shown that about 50% of the total CO 2 released was from the metabolism of the energy supply for biosynthesis, and the remaining from that for maintenance; thus, CO 2 production was considered to be partially associated with growth. The model fitted the experimental data as long as a net growth was observed (0–50 h). The coefficients for growth- and non-growth-associated CO 2 production were A=0.646 (dimensionless) and B=0.017 h −1, respectively. From the coefficients of the model and the CO 2 history data, the biomass kinetics has been reconstructed, and the calculated biomass concentrations agree fairly well with the experimental data. From this, measurement of the CO 2 evolved may be used as an indirect and non-intrusive method of monitoring fungal growth during the first 50 h of cultivation.

Effects of volatile compounds on arthrospore germination and mycelial growth of Geotrichum candidum citrus race

Three groups of volatile compounds, i.e., alcohols, aldehydes and esters, were tested for their effects on arthrospore germination and mycelial growth ofGeotrichum candidum citrus race, the causal agent of citrus sour rot. Alcohols (heptanol, octanol, nonanol, decanol, geraniol, citronellol) at a concentration of 1.0 μl/ml showed 60% or more inhibitory effects on both germination and mycelial growth of this pathogen. Among aldehydes tested, only citral had an inhibitory effect of more than 50%, while esters had no effect. The chain length of straight-chain (C6–C12) alcohols correlated with inhibitory effect, and nonanol (C9) was most active. Treatment with alcohols or citral prior to inoculation reduced colonization and maceration of lemon peel by this pathogen by 70% or more. Results suggested that alcohols or citral can probably be used to prevent the development of citrus sour rot.

Toxic action of citric acid onGeotrichum candidum

Citric acid had a toxic effect on the mycelial growth ofGeotrichum candidum. At equal pH, citric acid was more toxic than HCl but its effect was minimized by adding CaCl2. The results indicate that the toxic effect of citric acid is due to the undissociated component and its ability to sequester the essential cations present in the growth medium.

Extracellular and cell-bound lipase activity in relation to growth of Geotrichum candidum

The imperfect fungus Geotrichum candidum produced extracellular lipase in a basic peptone-salt medium. By adding olive oil or Tween 80 to the basic medium the lipase yields could be enhanced and the maximal yields were found with Tween 80, which resulted in a sixfold increase in extracellular lipase activity as compared with basic medium. During the early phase of growth in medium with olive oil the proportion of cell-bound activity was higher than that of extracellular activity, and a delay in the secretion of extracellular lipase was found. The proportion of cell-bound activity from growth in basic medium and in basic medium with Tween 80 was lower than that of extracellular activity during the entire growth phase. Analyses by polyacrylamide gel electrophoresis showed that the lipase activity from growth in all three media could be ascribed to equivalent protein bands at 57 000 and 61 000 daltons. Immunodiffusion showed that the cell-bound preparation contained lipase that was immunologically identical with purified extracellular lipase from G. candidum.

Inhibition ofGeotrichum candidum by bicarbonate

In a Sabouraud liquid medium system with NaHCO3 or KHCO3 at as low as 0.1% (w/v), the mycelial growth ofGeotrichum candidum was inhibited by greater than 90%. Bicarbonate may have a potential use as a microbial inhibitor in a variety of food systems.

Effect of osmotic and matric potential on radial growth of Geotrichum candidum

The diameters of 48-h-old Geotrichum candidum colonies on agar decreased markedly with decreasing water potential in the range of −1.0 to −2.5 MPa, but there was a slight increase from −0.5 to −1.0 MPa. Differences between the effects of KC1, polyethylene glycol (PEG) 400, or mannitol were small. This pattern was similar when G. candidum was grown on semipermeable membranes on agar, where the water potential is mainly osmotic, and when the fungus was grown on semipermeable membranes floating on media amended with PEG 20000, where the water potential is mainly matric. Dry weight accumulation by G. candidum on membranes on agar or on floating membranes at 48 h showed the same pattern as did colony surface area: a slight stimulation at −1.0 MPa and a decrease with further decreases in water potential. This differed from previous results with G. candidum in liquid shake culture, where no effect on dry weight accumulation between −0.5 and −2.5 MPa was observed in media amended with PEG 400 or mannitol.

The growth of Geotrichum candidum on whiskey distillery spent wash

A strain of the imperfect fungus Geotrichum candidum was selected for its ability to utilize the low-pH, high biochemical oxygen demand (BOD) waste generated by an Irish malt whiskey distillery. Growth of the organism on this complex medium, in both batch and continuous culture, showed a sequential assimilation of the major components with the most complete carbon assimilation (63.7%) being achieved in batch culture. Optimum temperature for the continuous culture of the organism was found to be 22°C; at this temperature and at a dilution rate of 0.125 h−1 a productivity of 2.24 g l−1 h−1 was obtained. Variations in organism morphology, produced by varying growth rate and nutritional or environmental factors, as well as the potential of the process for the production of single cell protein from carbohydrate-rich waste are discussed.

Nuclei, septation, branching and growth of Geotrichum candidum.

A study was made of growth, septation and branching in Geotrichum candidum, a mould which forms physiologically complete septa. A correlation was observed between septation and branch initiation; branches were almost invariably formed just behind septa. Primary branches and their parent intercalary compartments initially increased in length at an exponential rate before eventually attaining a constant rate of extension. The whole branching system (which eventually contained seven tips) produced by an intercalary compartment increased in length exponentially until it attained a total length of at least 1-5 mm. The total length and the number of nuclei of undifferentiated mycelia increased exponentially at the same specific growth rate. The results suggest that nuclei divide just before or just after arthrospore formation.