Screening of H+-ATPase deficient mutant of Lactobacillus delbrueckii subsp. Bulgaricus

Abstract:

[Objective] Wes identified a neomycin-resistant mutant with reduced membrane-bound H+-ATPase activity from L. delbrueckii subsp. bulgaricus originated from the traditional dairy product to develop a yoghurt starter culture with low post-acidification capacity. [Methods] API 50 CH identification system and 16s rDNA sequence analysis were applied to identify the strain isolated from the indigenous yoghurt. Neomycin was used to screen spontaneous neomycin-resistant mutants. H+-ATPase activity and metabolic dynamics were evaluated between the parent strain and mutants. [Results] One strain was identified as L. delbrueckii subsp. bulgaricus by API 50 CH identification system and 16s rDNA sequence analysis, coded as KLDS 1.9201. Two mutant strains were mutated from KLDS 1.9201 and coded as KLDS 1.9201-1, KLDS 1.9201-4. Compared with the parent strain, the H+-ATPase activity of the mutants KLDS 1.9201-1 and KLDS 1.9201-4 decreased by 46% and 60% respectively. After cultured in MRS broth for 24 h, metabolic efficiency of the initial glucose for the parent strain was 65%, the mutants were 41% and 31%, the lactic acid concentration in the culture for the parent strain was 26g/L, the mutants were 18g/L and 15g/L respectively. The cell density of the mutants was lower than that of the parent strain. [Conclusion] The mutants of L. delbrueckii subsp. bulgaricus with reduced membrane-bound H+-ATPase activity had low growth and acid production, which could be applied to develop yoghurt starter culture with lower post-acidification.