Evaluation of Selectivity of Culture Media for Probiotic Bacteria.

KATIA GIANNI DE CARVALHO LIMA; MARIA TERESA DESTRO; MARISA LANDGRAF; BERNADETTE DORA GOMBOSSY DE MELO FRANCO

Santiago

Congreso; VII Congresso Latino-americano de Segurança Alimentar; 2002

This study aimed to evaluate the selectivity of twenty culture media for probiotic bacteria, including Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus bulgaricus, Bifidobacterium bifidum and Streptococcus thermophilus. Freeze-dried cultures were reactivated in milk supplemented with glucose and yeast extract, and then surface-spread on MRS, M-17, LC, MRS pH 5.4 and MRS containing the following supplements: cysteine (Cys-MRS), lithium chloride and sodium propionate with (LP-Cys-MRS) and without cysteine (LP-MRS), threalose (T-MRS), maltose (M-MRS), dichloxacillin (A), lithium chloride (B) and cysteine (C) (ABC-MRS, 2ABC-MRS, 4ABC-MRS, A5BC-MRS, 2A5BC-MRS and 4A5BC-MRS), bile salts (BL-MRS), bile salts and gentamicin with (BL-OG-Cys-MRS) and without cysteine (BL-OG-MRS), gentamicin (OG-MRS), gentamicin and cysteine (OG-Cys-MRS). Selectivity was tested at 37oC and at 42oC, under aerobiosis and anaerobiosis (Anaerogen system) up to 72 hours. No selectivity was observed for MRS, MRS 5.4 and Cys- MRS, since all cultures grew on these media. Only L. acidophilus, L. casei and B. bifidum grew on M-MRS, BLMRS,BL-OG-MRS, BL-OG-Cys-MRS, OG-Cys-MRS and OG-MRS. Only L.casei and L. acidophilus grew on LC and T-MRS. Four media (LP- MRS, LP-Cys-MRS, ABC-MRS and 2ABC-MRS) were selective for L.casei and B. bifidum. 4ABC-MRS, A5BC-MRS, 2A5BC-MRS and 4A5BC-MRS were selective for B. bifidum. For all cultures, better growth was achieved at 37oC under anaerobiosis. At 42oC, L.casei did not grow in any media. These results indicate that supplementation of MRS with proper chemicals may turn this medium selective for different probiotic bacteria most commonly used in the dairy industry. Despite improving the growth, incubation under anaerobiosis has little effect on the electivity of these media.