Recovery of Indigenous probiotic Lactobacillus plantarum Mut-7 on healthy Indonesian adults after consumption of fermented milk containing these bacteria.

Probiotics are live microorganisms that confer health benefits on the host when administered in adequate amounts, such as to support the balance of gut microbiota. In this study, the selected indigenous probiotic strain, Lactobacillus plantarum Mut-7, was used as a starter culture to produce fermented milk. A total of 28 healthy Indonesian youngsters and adults (male/female: 16/12; age 19.4-22.9 years old; normal BMI range 18.6-22.7 kg/m2) were supplemented with the fermented milk. This study aimed to determine the recovery of L. plantarum Mut-7 through molecular analysis from the subjects feces after ingestion of 140 mL fermented milk containing 7.0 log10 CFU/ml of L. plantarum Mut-7 for 15 days. Molecular detection was performed using the rep-PCR technique and sequencing of DNA 16S rRNA. Consumption of fermented milk containing L. plantarum Mut-7 enabled reduction of total E. coli and Coliform non-E. coli in several subjects. It was able to increase the total LAB and total L. plantarum in subjects' feces. The number of L. plantarum and mesophilic LAB increased by 5.5 ± 1.6 log10 CFU/g, 1.8 ± 0.8 log10. On the other side, thermophilic LAB increased by 2.8 ± 3.0 log10 CFU/g in 23 out of 28 subjects. These findings proved that L. plantarum survived in the human gastrointestinal tract. Based on the molecular identification technique using rep-PCR technique and sequencing of gene 16S rRNA, two isolates had similarity to L. plantarum Mut-7 by a coefficient value of 100%. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13197-021-05046-z.

Construction of Lactobacillus plantarum strain with enhanced L-lysine yield.

AIM: To enhance L-lysine secretion in Lactobacillus plantarum. METHODS AND RESULTS: An S-2-aminoethyl-L-cystein (AEC)-resistant mutant of L. plantarum was isolated, and it produced L-lysine at considerably higher level than the parent strain. Aspartokinase in the mutant has been desensitized to feedback inhibition by L-lysine. The nucleotide sequence analysis of thrA2 that codes for aspartokinase in the mutant predicted a substitution of glutamine to histidine at position 421. L-Lysine-insensitive aspartokinase, together with aspartate semialdehyde dehydrogenase, dihydrodipicolinate synthase, and dihydrodipicolinate reductase genes, was cloned from L. plantarum DNA to a shuttle vector, pRN14, and the genes were then transformed individually into the AEC-resistant mutant and the parent strain. The overexpression of the genes led to the increase in the activity of enzymes they encode in vitro. However, only the strain overexpressing aspartokinase or dihydrodipicolinate synthase produced more L-lysine. CONCLUSIONS: The desensitization of aspartokinase to L-lysine in L. plantarum led to the overproduction of L-lysine. The overexpression of L-lysine-insensitive aspartokinase or dihydrodipicolinate synthase enhanced L-lysine secretion in L. plantarum. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of the L-lysine-overproducing strain of L. plantarum in food or feed fermentation may increase the L-lysine content of fermented products.