Microbial Biotechnology
Electronic Journal of Biotechnology ISSN: 0717-3458 Vol. 13 No. 5, Issue of September 15, 2010
© 2010 by Pontificia Universidad Católica de Valparaíso -- Chile Received February 25, 2010 / Accepted June 2, 2010
DOI: 10.2225/vol13-issue5-fulltext-16  
RESEARCH ARTICLE

Improved growth model for two-stage continuous cultures of Lactobacillus helveticus

Abdallah Bouguettoucha
Faculté des Sciences de l’Ingénieur
Université Ferhat Abbas
Sétif, Algeria

Béatrice Balannec
Ecole Nationale Supérieure de Chimie de Rennes
Université de Rennes 1
Rennes, France
Université Européenne de Bretagne

Saci Nacef
Ecole Nationale Supérieure de Chimie de Rennes
Université de Rennes 1
Rennes, France
Université Européenne de Bretagne

Abdeltif Amrane*
Ecole Nationale Supérieure de Chimie de Rennes
Université de Rennes 1
Rennes, France
Université Européenne de Bretagne
E-mail: abdeltif.amrane@univ-rennes1.fr

*Corresponding author

Keywords: continuous culture, growth, lactic acid fermentation, substrate limitation, unstructured models.

Abbreviations:

A: coefficient for growth-associated production (dimensionless)
B: coefficient for non-growth-associated production (h-1)
D: dilution rate (h-1)
F: flow rate (L h-1)
GM: general model
[HL]: undissociated lactic acid concentration (g L-1)
[L-]: dissociated lactic acid concentration (g L-1)
p: total lactic acid concentration (g L-1)
qp: specific production rate (h-1)
s: carbon substrate concentration (g L-1)
RSD: residual standard deviation
SLM: substrate limitation model
t: time (h)
V: volume (L)
x: biomass concentration (g L-1)
YP/S: product on substrate yield
α and β: added parameters in the exponential expression for dilution rate in the second stage Dc
µ: specific growth rate (h-1)
Subscripts    
0:initial
i: seed culture (first stage)
c: culture (second stage)        
calc: calculated
exp: experimental
f: final
inh: inhibitory
lim: limiting
max: maximum
Abstract   Full Text

An unstructured model for growth and lactic acid production during two-stage continuous cultures of Lactobacillus helveticus was previously developed. The Verlhust model was considered to describe growth kinetics. Production models was based on modified Luedeking-Piret expressions involving an inhibitory effect for the first stage (seed culture) and a nutritional limitation effect for the second stage (culture). To account for the decrease of the biomass concentration observed in the second stage, the dilution rate Dc was replaced by an exponential term of the dilution rate in the growth and product relations. Contrarily to the previous model, the important decrease of the biomass concentration observed at steady state in the second stage at high dilution rates, namely close to wash out, was correctly described by the new model. It also proved to satisfactory describes production data and volumetric productivity.
Supported by UNESCO / MIRCEN network