Mise au point de la production d'acide lactique par lactobacillus delbruechi subsp , bulgaricus à partir de lactoserum

Abstract

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.