ORIGINAL PAPER

Applied Microbiology and Biotechnology

, Volume 49, Issue 6, pp 682-690

Modelling the influence of pH, temperature, glucose and lactic acid concentrations on the kinetics of lactic acid production by Lactococcus lactis ssp. lactis ATCC 19435 in whole-wheat flour

  • C. ÅkerbergAffiliated withDepartment of Chemical Engineering 1, Lund Institute of Technology/Lund University, P.O. Box 124, SE-221 00 Lund, Sweden Tel.: +46 46 2228297 Fax: +46 46 2224526 e-mail: Guido.Zacchi@kat.lth.se
  • , K. HofvendahlAffiliated withDepartment of Applied Microbiology, Lund Institute of Technology/Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
  • , G. ZacchiAffiliated withDepartment of Chemical Engineering 1, Lund Institute of Technology/Lund University, P.O. Box 124, SE-221 00 Lund, Sweden Tel.: +46 46 2228297 Fax: +46 46 2224526 e-mail: Guido.Zacchi@kat.lth.se
  • , B. Hahn-HägerdalAffiliated withDepartment of Applied Microbiology, Lund Institute of Technology/Lund University, P.O. Box 124, SE-221 00 Lund, Sweden

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Abstract

A kinetic model of the fermentative production of lactic acid from glucose by Lactococcus lactis ssp. lactis ATCC 19435 in whole-wheat flour has been developed. The model consists of terms for substrate and product inhibition as well as for the influence of pH and temperature. Experimental data from fermentation experiments under different physical conditions were used to fit and verify the model. Temperatures above 30 °C and pH levels below 6 enhanced the formation of by-products and d-lactic acid. By-products were formed in the presence of maltose only, whereas d-lactic acid was formed independently of the presence of maltose although the amount formed was greater when maltose was present. The lactic acid productivity was highest between 33 °C and 35 °C and at pH 6. In the concentration interval studied (up to 180 g l−1 glucose and 89  g l−1 lactic acid) simulations showed that both substances were inhibiting. Glucose inhibition was small compared with the inhibition due to lactic acid.