Comparative genomic analyses reveal carbohydrates-rich environment adaptability of Lentilactobacillus laojiaonis sp. nov. IM3328

Screening the Protective Agents Able to Improve the Survival of Lactic Acid Bacteria Strains Subjected to Spray Drying Using Several Key Enzymes Responsible for Carbohydrate Utilization

“…Secondly, the down-regulation of the glycolysis pathway and cysteine metabolism pathway directly impaired the expressions of pyruvate synthase ( pyk ) encoding PK, as well as cystathionine β-lyase ( metC ), which generated more pyruvate to enter into the glycolysis process [ 18 , 31 ]. At the same time, the expression of L-lactate dehydrogenase ( ldh ) was down-regulated, causing the imbalance of the pyruvate metabolism pathway [ 15 ]. Obviously, the down-regulated expressions of pyruvate synthase ( pyk ) and L-lactate dehydrogenase ( ldh ) led the PK and LDH activity of strain NCFM after spray drying to be decreased, as observed in Section 3.3.3 and Section 3.3.4 .…”

“…Strain NCFM down-regulated such glycolysis pathways as the pyruvate synthase ( pyk )-encoding PK protein and L-lactate dehydrogenase ( ldh )-encoding LDH protein pathways in the presence of 1% ( w / v ) RSM during spray drying [ 41 , 42 ], but the presence of 10% ( w / v ) RSM significantly up-regulated the PTS transporter and pyruvate metabolism of strain NCFM. The up-regulated PTS transporter and pyruvate as an intermediate link of energy and sugar metabolism should be quite beneficial for the improvement of strain NCFM’s carbohydrate utilization, which produces enough energy to respond to a hostile environment due to the enhancement of enzyme activity [ 15 , 42 ]. The transcriptomic data from strain NCFM explain how the key glycolytic enzymes PK and LDH respond to spray drying and perhaps could be used as key indicators to screen the desirable protective agents for bacterial cells.…”

“…Furthermore, HK and PK, as crucial enzymes responsible for carbohydrate utilization, contribute to the conversion of glucose into pyruvate, an important intermediate in the final stages of the LAB fermentation process. The conversion of pyruvate to lactic acid also represents a significant pathway for LAB to generate NAD and ATP under the catalysis of LDH [15]. Moreover, a study by Zhang et al (2019) reported the utilization of β-GAL liposome model as a substitute for Lactobacillus cells in the optimization of a protective agent for spray drying [16].…”