Abstract

The aim of this study is to determine the effect of certain prebiotics on the synthesis of bacteriocins. The Lactobacillus paracasei CMGB16 strain producing bacteriocins was used.Escherichia coli was used as the sensitive strain. In the nutritive environment (MRS); the carbon source (glucose) was supplemented with inulin from chicory and Dahlia, raffinose and lactulose. The cells were eliminated using centrifuge at 5,000 rpm for 10 min. The pH of the resulted supernatant was adjusted to the value of 5.5 with NaOH 0.2N and the inhibitory activity was determined by agar well diffusion method. The resistance to various inhibitory substances (pepsin, trypsin, pronase E, subtilisin, catalase) was also determined in concentration of 0.5 mg/ml. These tests were also performed with the fluid concentrated up to 1:3, at 48°C, 200 rpm and 100 mbar. The strains were cropped in these environments for 96 h. Thus, the witnessed strain is sensitive to the bacteriocin produced by the L. paracasei. A significant increase of the activity of the bacteriocin was noticed when supplementing the cropping environment with inulin, lactulose and raffinose, within the time range of 25 - 96 h. The diameter of the inhibition area was at least 2 cm visible in the use of all prebiotics. The largest inhibitory area was visible after 48 and 72 h of fermentation.

Key words: Bacteriocin, prebiotic, Escherichia coli, lactulose.