Résumé:
The production of lactic acid from whey represents an important means to
overcome pollution . More ever, it provides an essential raw material for
pharmaceutical and food industries.
For selecting influencing factors for lactic acid production by Lb. bulgaricus , an
experimental design based on Plackett and Burman matrix has been used.
Among the seventh factors investigated : pH, lactose concentration, yeast extract
and corn steep liquor were found to have a significant effect on the lactic acid
production. More ever, pH and corn steep liquor were found to have a significant
effect on the yield.
The optimum values of pH, yeast extract, K2HP04, MgS04, MnS04, FeS04 have
been determined by a central composite design of Box and Wilson (1951) as
follows: 5.5, 1.6 g/l, 2.7 g/l, 0.124 g/l, 0.031 g/l,and 0.012 g/l respectively.
Depending on the mentionned values wich were determined in flasks, a kenitic
study of the production of lactic acid by batch fermentation in 2 litres fermentor
has been conducted and the kenitic parameters (p, n, m, a, p) have been
determined.
This fermentation produced 36.45 g/l and 34 g/l of lactic acid, using autoclved
whey and filtrated whey respectively, starting from 45.02 g/l and 43.7 g/l of
lactose, representing a yield of 77.8% and 81% and a reproductivity of 2 g/l/h.