Selective Breeding of Oxygen-Tolerant and Oxalate-Degrading Lactic Acid Bacteria by Protoplast Fusion

Abstract

Bifidobacterium lactis with oxalate-degrading capacity can efficiently reduce the oxalate in vivo, and it can be used to prevent and treat kidney stone diseases. While Bifidobacterium lactis is poorly oxygen-tolerant, which hinders it from being as microbial ecological agents. To obtain oxygen-tolerant and oxalate-degrading lactic acid bacteria, protoplast fusion technology was used between B. lactis and L. acidophilus. Under the optimum conditions of protoplast fusion with PEG 6000 concentration 50%, the fusion time 7 min, the fusion temperature 30°C, the concentration of CaCl2 0. 02mol/ L and the concentration of MgCl2 0.5mol/ L, the fusion rate reached 7.6%, and three oxygen-tolerant fusant showing that the level of oxalate degradation were similar with B. lactis was obtained. The fusants of SZY1-7 and SZY2-1 could tolerance to pH 2.5 and 0.5% (w/v) bile salt.