Tolerância ao congelamento em mutantes de Lactobacillus delbrueckii UFV H2b20 / Resistance to freeze in mutants of Lactobacillus delbrueckii UFV H2b20

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Mutants of Lactobacillus delbrueckii UFV H2b20 were isolated after treatment with ultra violet light, acridine orange, or ethyl methane sulfonate. After the mutagenic treatments, ten colonies were picked randomly from each treatment and were the mutants characterized. Specific growth rate () and survival to successive freeze-thaw cycles were assessed for each isolate along with milk acidification rate and survival to storage at – 20 C with different crioprotective agents. Among all 30 isolates, mutants MUV9, MAC6, and MEMS2 displayed higher values and better survival after repeated freezethaw cycles. Survival of the mutant strains after 15 days at – 20 C, both in the presence and the absence of cryoprotective, was better than survival of the wild type. Reconstituted non fat milk (10 %) proved to be a better cryoprotective agent than saccharose and monosodium glutamate for storage at – 20 C. Survival rates were higher for mutants MAC6 and MEMS2, after 15 days at – 20 C. Cold shock, at 10 C for four-hours, and heat shock, 50 C for 30 minutes, enhanced survival of the mutant strains and also of the parental strain as measured after 70 days at – 20 C. Cold shock response allowed better survival to all the strains, mutant and parental, when compared to the heat shock. The results reported here show that strain development of L. delbrueckii UFV H2b20 for technological purposes can be achieved by a classical genetic mutation.

ASSUNTO(S)

mutantes survival mutants congelamento ciencia e tecnologia de alimentos sobrevivência freeze

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