Cloning of the D‐lactate dehydrogenase gene from Lactobacillus delbrueckii subsp. bulgaricus by complementation in Escherichia coli

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Abstract
A strain of Escherichia coli (FMJ144) deficient for pyruvate formate lyase and lactate dehydrogenase (LDH) was complemented with a genomic DNA library from Lactobacillus delbrueckii subsp. bulgaricus. One positive clone showed LDH activity and production of D(−)lactate was demonstrated. The nucleotide sequence of the D‐LDH gene (ldhA) revealed the spontaneous insertion of an E. coli insertion sequence IS2 upstream of the gene coding region. The open reading frame encoded a 333‐amino acid protein, showing no similarity with known L‐LDH sequences but closely related to L. casei D‐hydroxyisocaproate dehydrogenase (D‐HicDH).