Article Abstract:
Lactococcus lactis subsp. cremoris MG1363 mutants lacking the aldB gene produce a large amount of diacetyl. The aldB gene encodes alpha-acetolactate decarboxylase and is deleted by double crossover homologous recombination. The mutants accumulate a large amount of alpha-acetolactate that is oxidatively decarboxylated to diacetyl. The overexpression of the ilvBN genes that encode alpha-acetolactate synthase in the mutants further increases diacetyl production. The diacetyl production in the mutants is comparable to that in L. lactis subsp. lactis biovar diacetylactis.
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Article Abstract:
The diversity of the Lactococcus lactis subsp. lactis IL1403 beta-galactosidase phenotype-negative selection on solid media containing cellobiose or lactose and X-Gal was presented and several genes essential for lactose assimilation were identified. The analysis revealed that although phospho-beta-glucosidase, a gene essential for lactose assimilation is homologous to a putative phospho-beta-glucosidase, it also exhibits phospho-beta-glucosidase activity and is the major enzyme in Lactococcus lactis IL1403 in lactose hydrolysis.
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Article Abstract:
New means of examining the relation between the Lactoccus lactis subspecies cremoris and lactis are presented. Southern hybridization analysis using cloned chromosomal genes as probes was used to assess the bacteria. It was found that two distinctgroups are formed by the two subspecies while a 20 to 30% sequence divergence is estimated between the two. This DNA homology is the basis for the call for anew classification between the groups.
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