Catabolism of Serine by Pediococcus acidilactici and Pediococcus pentosaceus

Abstract

ABSTRACTThe ability to produce diacetyl from pyruvate andl-serine was studied in various strains ofPediococcus pentosaceusandPediococcus acidilacticiisolated from cheese. After being incubated on both substrates, onlyP. pentosaceusproduced significant amounts of diacetyl. This property correlated with measurable serine dehydratase activity in cell extracts. A gene encoding the serine dehydratase (dsdA) was identified inP. pentosaceus, and strains that showed no serine dehydratase activity carried mutations that rendered the gene product inactive. A functionaldsdAwas cloned fromP. pentosaceusFAM19132 and expressed inEscherichia coli. The purified recombinant enzyme catalyzed the formation of pyruvate froml- andd-serine and was active at low pH and elevated NaCl concentrations, environmental conditions usually present in cheese. Analysis of the amino acid profiles of culture supernatants fromdsdAwild-type anddsdAmutant strains ofP. pentosaceusdid not show differences in serine levels. In contrast,P. acidilacticidegraded serine. Moreover, this species also catabolized threonine and produced alanine and α-aminobutyrate.