The substrate carbon consumption and metabolite production to describe the growth of Geotrichum candidum and Penicillium camemberti on glucose and amino acids (original) (raw)
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Diauxic growth of Geotrichum candidum and Penicillium camembertii on amino acids and glucose
Brazilian Journal of Chemical Engineering, 2012
The purpose of this work was to examine physiological differences between the yeast Geotrichum candidum and the mould Penicillium camembertii, organisms involved in the industrial process of cheese ripening. Three groups of amino acids had previously been characterized, based on their carbon assimilation and dissimilation by the two fungal species. For both of them, a diauxic growth phase had been shown for a group of amino acids, which however had not been examined in light of physiological differences between the two microorganisms. In this work, the higher level of enzymatic activities of P. camembertii if compared to G. candidum was confirmed since a continuous and sequential use of both carbon substrates, glucose and arginine, was recorded during P. camembertii culture; while after glucose depletion, a clear stationary phase was recorded before the assimilation of the considered amino acid as both carbon and nitrogen sources by G. candidum. This behaviour was confirmed for the three amino acids tested, i.e., arginine, proline and glutamic acid. Contrarily, during the two growth phases, on glucose and the test amino acid, respectively, higher growth rates were recorded for G. candidum compared to P. camembertii, showing higher substrate utilisation efficiency by G. candidum. Improving the knowledge regarding the metabolization of amino acids might be helpful in designing strategies aiming at improving processes such as cheese ripening. The work should be followed up by similar works using small peptides.
Carbon assimilation and dissimilation during growth ofGeotrichum candidum on amino acids and glucose
Journal of Chemical Technology & Biotechnology, 2007
BACKGROUND: This work examines the metabolic behaviour of amino acids during Geotrichum candidum growth, in the presence of a primary carbon source like glucose. Amino acids were characterized based on their carbon assimilation and dissimilation by G. candidum, in the presence of glucose as the limiting substrate. RESULTS: The first group (Cys, His, Phe, Thr and Trp) was only used as nitrogen sources by G. candidum, with glucose being the carbon and energy source. Glucose repression was shown for the rest of the amino acids, since only after glucose depletion amino acids from the second group (Gly, Lys, Met, Val) were dissimilated for energy supply by oxidation into CO 2 , while those from the third group (Ala, Arg, Asp, Glu, Leu, Pro and Ser) were assimilated as carbon sources (and additionally used as nitrogen sources), leading to a diauxic growth. CONCLUSION: This energy-saving response was not previously shown for the second fungus involved in ripening of soft white cheese-P. camembertii-leading to simultaneous use of some amino acids and glucose as carbon and energy sources, and hence lower growth rates than those recorded during G. candidum growth.
Journal of Chemical Technology & Biotechnology, 2008
BACKGROUND: Three groups of amino acids were previously characterized based on their ability to be assimilated as carbon source by Penicillium camembertii. To describe the diauxic growth recorded on glucose and amino acids from the second group, such as arginine, an unstructured model was previously developed, based on the sequential consumption of both carbon substrates, glucose, followed after its exhaustion, by arginine. The model was modified to describe also the behaviour recorded during growth on other amino acids. RESULTS: The growth model involved the carbon substrate consumption (Verlhust model) and the biomass on carbon substrate yield. Glucose was therefore considered during P. camembertii growth on nitrogen source amino acids (lysine-first group); and amino acid consumption was considered during growth on carbon source amino acids (glutamate-third group), with glucose being dissimilated only for energy supply. The excess nitrogen from amino acids was released as ammonium; the linking of this production to growth was found to increase with the ability of the amino acid to be assimilated as carbon source by P. camembertii. CONCLUSION: The various metabolic behaviours recorded during P. camembertii growth on amino acids, in the presence of a primary carbon source such as glucose, were proved to be satisfactorily described by the model, showing the robustness of the model.
Journal of Biotechnology, 2002
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 DpH 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.
Applied Microbiology and Biotechnology, 2002
Geotrichum candidum and Penicillium camembertii were cultivated on the surface of a gelified medium, simulating the composition of the aqueous phase of a Camembert cheese. The relation of their growth with substrate consumption (carbon or nitrogen), metabolite production (ammonia), or proton transfer (deduced from pH by means of the buffer capacity of the medium) was examined. The coefficients associated with cellular biosynthesis and resulting from cellular maintenance were determined. From these coefficients and the considered substrate utilization or metabolite production kinetics, the growth kinetics were reconstructed until the end of growth. The model allowed analysis of biosynthesis and cellular maintenance contributions to the considered kinetics. At the end of growth, almost all the peptone was used for G. candidum biosynthesis, while most of the lactic acid (62%) was used for cellular maintenance. P. camembertii metabolized fewer amino acids as carbon sources, resulting in use of peptone for maintenance (12%), and lactic acid (80%) for cell biosynthesis. For both microorganisms, ammonia production was growthassociated, since this production resulted from the deamination of carbon-and nitrogen-source amino acids, in close relation with peptone consumption.
Geotrichum candidum Geo17 was cultivated on peptones as carbon and nitrogen source, and in the presence of lactate as the second carbon source. From the analysis of the initial and final culture medium after total hydrolysis, the yield of consumption was determined for each amino acid. Amino acids have been considered a convenient carbon source for biosynthesis, while the rest of the amino acids were assumed to be used only as a nitrogen source, with the corresponding carbon released as CO 2 resulting from energy supply. Carbon mass balances confirmed this assumption. A clear differentiation between the amino acids assimilated as carbon sources and those assimilated as energy sources was therefore highlighted.
Carbon and nitrogen yields during batch cultures of Geotrichum candidum and Penicillium camembertii
Process Biochemistry, 2004
Batch cultures of Geotrichum candidum and Penicillium camembertii were carried out on peptones as carbon and nitrogen source and in the presence of lactate as a second carbon source. Unless growth ceased, carbon and nitrogen yields remained constants, except yields involving lactate consumption by G. candidum, since this fungus preferentially metabolized peptones as a carbon source. For both fungi, nearly 40% of the available carbon was metabolized for cellular biosynthesis and the remainder (about 60%) as carbon dioxide, for the energy supply of both biosynthesis and viable cell maintenance. Moreover, in relation to their carbon content, amino acids contain excess nitrogen, which was released as ammonium. From all these, the yields of ammonium nitrogen on cellular nitrogen were in all cases higher than 1, and were especially high when the medium contained only peptones as a carbon source, 4.4 and 5.7 for G. candidum and P. camembertii respectively. Indeed, in this case, the excess nitrogen was especially pronounced.
Enzyme and Microbial Technology, 2002
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.
Journal of Chemical Technology & Biotechnology, 2002
An unstructured model has been developed to predict microbial growth based on carbon or nitrogen substrate consumption, ammonia or carbon dioxide production and proton transfer. The model has been validated for batch cultures of Geotrichum candidum and Penicillium camembertii growing on peptones and peptones þ lactate based media. The contributions of the considered kinetics to biosynthesis and cellular maintenance can be deduced from this model. The nitrogen source (peptones) was mainly utilized in biosynthesis: for P camembertii growing on peptones, 86% of the metabolized peptones. G candidum metabolized peptones preferentially to lactate as a carbon source, resulting in lactate utilization by a maintenance mechanism during the stationary state. In contrast, P camembertii, which metabolized fewer amino acids as a carbon source, utilized lactate mainly for biosynthesis (83% of the consumed lactate). Most (up to 71%) of the ammonia released was produced by deamination of amino acids utilized as both carbon and nitrogen sources by growth-associated metabolism. With peptones, proton transfer resulted from ammonia release, most likely as a result of the growth-associated mechanism, as supported experimentally (55-58% of the released ammonia for both microorganisms). The contribution of lactate to proton transfer resulted in 76% of protons exchanged by a growth-associated mechanism during P camembertii growth. For total carbon dioxide production, the contributions of the energy supplies for biosynthesis and cell maintenance were similar; except during P camembertii growth in the presence of lactate (65% of growth-associated CO 2 production).
Amino acids as carbon, energy and nitrogen sources forPenicillium camembertii
Journal of Chemical Technology & Biotechnology, 2006
Three groups of amino acids were previously characterized on their ability to be assimilated as carbon source by Penicillium camembertii. In view of a deeper understanding of their metabolic behaviour, growth of P. camembertii on glucose, the limiting substrate, and an amino acid was examined in batch culture. Amino acids from the first group (Cys, His, Lys, Met, Trp and Val) are convenient nitrogen sources, but cannot be assimilated as carbon sources. However, they are also dissimilated, namely used for energy supply by oxidation into CO 2 , during stationary phase, after glucose depletion, as shown for lysine; and the corresponding nitrogen was released as ammonium. Growth exhibited diauxic behaviour for the second group of amino acids (Arg, Leu), since they can be assimilated as carbon sources, in addition to their assimilation as nitrogen sources, but only after glucose depletion, as shown for arginine. A clear differentiation between the assimilated and the dissimilated carbon was demonstrated for the third group of amino acids (Ala, Asp, Glu, Gly, Pro, Ser, Thr); it was shown that the carbon from glutamic acid was assimilated, while the carbon from glucose was dissimilated.