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

摘要

A kinetic model of the fermentative production of lactic acid from glucose by Lactococcus lactis subsp. lactis ATCC 19435 in whole-wheat flour was developed. The model included terms for substrate and product inhibition as well as for the influenceof pH and temperature. Data from fermentation experiments conducted at 30, 33.5, 37 or 40deg C using hydrolysed flour or glucose-supplemented flour media at a pH of 4.0, 5.0 or 6.0 were used to fit and verify the model. By-products were formed in the presence of maltose only, whereas 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 and 35deg C and at pH 6. In the concentration interval studied (up to 180 g/litre glucose and 89 g/litre lactic acid) simulations showed that both substrate and product inhibition were present; however, glucose inhibition was small compared with the inhibition due to lactic acid.