Integrated analysis of physiology, antioxidant activity and transcriptomic of Lactobacillus plantarum 120 in response to acid stress

This research examined the effects of acid stress on the physiological and antioxidant activity of Lactobacillus plantarum 120 (Lp-120) and explored its underlying mechanisms. The results revealed that the survival rates of the strain significantly decreased as the pH decreased from 5.5 to 4.5. Meanwhile, the ATP concentrations of the strain decreased from 0.51 to 0.12, and the reactive oxygen species levels rose 1.26-fold with a decrease in pH. However, as the pH decreased, the free radical (DPPH, O-2(-), and OH-) scavenging activity, reducing power, superoxide dismutase, glutathione peroxidase activities, and the total antioxidant capacities of Lp-120 all increased (P < 0.05). Among them, the DPPH scavenging power and superoxide radical scavenging power reached the highest value of 35.5% and 30.74% respectively at pH 4.5, and the hydroxyl radical scavenging power reached the highest value of 53.2% at pH 5.0, which indicated that appropriate acid stress could improve the antioxidant activities of the strain. Transcriptomics data showed that the expression levels of genes (ndh, trxA, etc.) were upregulated (0.39-10.54-fold) under acid stress, which related to the "NADH oxidase/NADH peroxidase" system, glutaredoxin system and thioredoxin system. Taken altogether, this study brought valuable insights for enhancing the antioxidant activities of Lp-120 and provided valuable information on the application of Lactobacillus plantarum as antioxidant starter cultures in fermented foods.