Heterologous Expression of gadA and speA from Alicyclobacillus acidoterrestris Enhances the Acid Resistance and Fermentative Activity of Lactiplantibacillus plantarum

Enhancing the acid tolerance of Lactiplantibacillus plantarum is essential for improving its fermentation performance and metabolic activity under acidic conditions, thereby strengthening its probiotic functionality. In this study, the glutamate decarboxylase gene (gadA) and the arginine decarboxylase gene (speA) from Alicyclobacillus acidoterrestris DSM 3922T were heterologously expressed in L. plantarum WCFS1 to enhance its acid resistance. Recombinant expression vectors pMG36e-gadA and pMG36e-speA were constructed and introduced into L. plantarum WCFS1 via electroporation. The acid tolerance, cell membrane integrity, intracellular pH, ATP content, gene expression profiles, and enzyme activities of the recombinant L. plantarum WCFS1-gadA and WCFS1-speA were systematically evaluated. The results demonstrate that both recombinant strains exhibited significantly higher acid tolerance than the control strains. Under acid stress, the expression of gadA and speA was up-regulated, accompanied by enhanced activities of glutamate and arginine decarboxylases. In addition, the recombinant strains maintained higher intracellular pH and ATP levels compared with the control strain. Furthermore, the fermentative activity results support their potential applicability in fruit juice fermentation. Collectively, the heterologous expression of gadA and speA effectively improved the acid tolerance of L. plantarum, providing both mechanistic insights into acid stress adaptation and a theoretical basis for developing industrially robust, acid-resistant probiotic strains.