Production optimization and in vitro evaluation of the biofunctional potential of folate from Lactiplantibacillus plantarum-MGKMVIT11

Introduction Folate-producing probiotic bacteria have gained considerable attention due to their potential therapeutic and health-promoting benefits. In the present study, a folate-producing probiotic strain, Lactiplantibacillus plantarum MGKMVIT11, isolated from fermented fresh peel of Sechium edule (chayote), was evaluated for its probiotic characteristics, folate production, and biological activities. Methods The probiotic potential of the isolate was assessed through acid and bile tolerance, auto-aggregation, co-aggregation, cell surface hydrophobicity, antibiotic susceptibility, and antibacterial activity analyses. Folate production was optimized using a sequential statistical approach involving one-factor-at-a-time (OFAT) experiments followed by Plackett-Burman (PB) and response surface methodology (RSM) based on central composite design (CCD). Furthermore, the antioxidant and anti-inflammatory activities of the produced folate were evaluated through DPPH radical scavenging assay, reducing power assay, and cytokine expression analysis in LPS-induced U937 cells. The interaction effect of folate in combination with Paclitaxel was also investigated using HCT-116 cells. Results and discussion Lactiplantibacillus plantarum MGKMVIT11 exhibited significant probiotic properties with high acid tolerance (75.32 ± 0.95%) and bile salt tolerance (78.16 ± 2.53%). The strain demonstrated notable auto-aggregation (70.32 ± 0.95%), co-aggregation (68.51 ± 2.88%), and cell surface hydrophobicity (48.37 ± 4.0%). It also showed susceptibility toward seven antibiotics and strong antibacterial activity against foodborne pathogens, particularly Salmonella enterica with a zone of inhibition of 17.1 ± 0.22 mm. OFAT optimization established maltose, peptone, pH 7, 25°C, and 4% inoculum as suitable baseline conditions, while CCD-based RSM identified maltose, ((NH 4 ) 2 SO 4 ), and MgSO4 as significant variables influencing folate production. Increasing maltose concentration significantly enhanced folate yield. Under optimized conditions, folate production reached 364.35 μg/mL at 24 h, representing 98% agreement with the predicted value (370.99 μg/mL) and a 1.64-fold enhancement compared with unoptimized conditions. In addition, the produced folate exhibited considerable antioxidant activity through enhanced DPPH radical scavenging and reducing power. Anti-inflammatory activity was confirmed by decreased IL-6 and TNF- α , levels along with a slight increase in IL-10 expression in LPS-treated U937 cells. Furthermore, the combination of folate with Paclitaxel demonstrated promising interaction effects against HCT-116 cells, suggesting its potential therapeutic applicability.