Extracellular secretion of a maltogenic amylase from Lactobacillus gasseri ATCC33323 in Lactococcus lactis MG1363 and its application on the production of branched maltooligosaccharides.

A maltogenic amylase gene from Lactobacillus gasseri ATCC33323 (LGMA) was expressed in Lactococcus lactis MG1363 using the P170 expression system. The successful production of recombinant LGMA (rLGMA) was confirmed by the catalytic activity of the enzyme in liquid and solid media. The N-terminal amino acid sequencing analysis of the rLGMA showed that it was Met-Gln-Leu-Ala-Ala-Leu-, which was the same as that of genuine protein, meaning the signal peptide was efficiently cleaved during secretion to the extracellular milieu. The optimal reaction temperature and pH of rLGMA (55 degrees C and pH 5, respectively) and enzymatic hydrolysis patterns on various substrates (beta-cyclodextrin, starch, and pullulan) supported that rLGMA was not only efficiently secreted from the Lactococcus lactis MG1363 but was also functionally active. Finally, the branched maltooligosaccharides were effectively produced from liquefied corn starch, by using rLGMA secreted from Lactococcus lactis, with a yield of 53.1%.