Preliminary study of lactic acid production from inulin hydrolysates using Lactobacillus acidophilus LA-5

Lactic acid is widely used in the chemical industry, food industry, cosmetics, and pharmaceuticals. The main objective of the present work was chemical and enzymatic inulin hydrolysis from inulin rich feedstock (dahlia and Jerusalem artichoke) followed by hydrolysates fermentation to lactic acid using Lactobacillus acidophilus LA-5. Chemical hydrolysis of Jerusalem artichoke and dahlia flour was performed with concentrated H2SO4 for one hour at 100°C at different pH of the medium, and the amount of reducing sugars obtained varied between 0.10 to 0.51 g fructose/g dry weight flour for Jerusalem artichoke and between 0.099 to 0.448 g fructose/g dry weight flour for dahlia. The enzymatic hydrolysis was performed by varying the substrate concentration and the pH, and the amount of reducing sugars produced was between 0.439 to 0.56 g fructose/g dry weight flour for Jerusalem artichoke and between 0.435 to 0.522 g fructose/g dry weight flour for dahlia flour. The hydrolyzed substrates were then fermented with a commercial culture of Lactobacillus acidophilus LA-5 for 96 hours. Lactic acid production was monitored and recorded every 24 hours, measuring the pH and total acidity of the samples. The obtained results were then analyzed using Principal Component Analysis. An optimum number of 4 principal components are enough to explain 87.1% of data variation for calibration and 69.8% for validation. PC-1 is given by the acidity evolution, correlated with pH drop during fermentation. The lactic acid accumulation was maximum in the third day of fermentation (after 48 hours) for both dahlia and Jerusalem artichoke.