On-line analysis and modeling of microbial growth using a hybrid system approach

J of Chemical Tech & Biotech

2005

Growth of Lactobacillus helveticus on supplemented whey permeate was divided into five phases: lag, exponential, deceleration, stationary and decline phases. Each phase was characterized by simple model kinetics. From this and by considering a partial association of lactic acid production with growth, with an additional term introduced to account for cessation of production when the carbon substrate became limiting, the lactic acid production was analytically deduced for each growth phase. For both growth and production data, on the whole culture, the calculated values were found to match experimental data. All the model parameters can be easily deduced from experimental data. The model allows therefore a fine analysis of growth and production kinetics.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of the kinetics of growth and lactic acid production for Lactobacillus helveticus growing on supplemented whey permeate

J of Chemical Tech & Biotech

2005

“…Mycelial growth can be described using the widespread logistic or Verlhust relation (Moraine and Rogovin, 1966;Norton et al, 1994;Diaz et al, 1999;Pandey et al, 2000):…”

Section: Determination Of the Concentration Gradientsmentioning

confidence: 99%

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

Aldarf

Fourcade

Biotech & Bioengineering

et al. 2004

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.

“…Mycelial growth can be described using the widespread logistic or Verlhust relation [13,[25][26][27] (Fig. 1):…”

Section: Resultsmentioning

confidence: 99%

Substrate and metabolite diffusion within model medium for soft cheese in relation to growth of Penicillium camembertii

Aldarf

Fourcade

J IND MICROBIOL BIOTECHNOL

et al. 2006

Penicillium camembertii was cultivated on a jellified peptone-lactate based medium to simulate the composition of Camembert cheese. Diffusional limitations due to substrate consumption were not involved in the linear growth recorded during culture, while nitrogen (peptone) limitation accounted for growth cessation. Examination of gradients confirmed that medium neutralization was the consequence of lactate consumption and ammonium production. The diffusion of the lactate assimilated from the core to the rind and that of the ammonium produced from the rind to the core was described by means of a diffusion/reaction model involving a partial linking of consumption or production to growth. The model matched experimental data throughout growth.