Biocontrol of Bacillus cereus by Lactobacillus planetarium in Kareish cheese and yogurt

This study aims to biocontrol of Bacillus cereus by Lactobacillus planetarium in Kareish cheese and yogurts. The minimum inhibitory concentrations (MICs), antioxidant potentials, total flavonoids content (TFC) and total phenolic content (TPC) of L. planetarium were also estimated. Results showed that incidence of B. cereus in Kareish cheese and yogurt was 16 and 4%, respectively. Four virulence genes were investigated by PCR in B. cereus isolates (n = 10). Two toxin producing genes, cytotoxin K (cytK), and phosphatidylcholine-hydrolyzing phospholipase C (Pc-plc), were detected in all B. cereus, whereas enterotoxigenic (nhe) and hemolysin BL (hbl) genes were detected in 90 and 50%, respectively. All isolates were vulnerable to erythromycin and gentamicin (100%) with intermediate sensitivity to ciprofloxacin and complete resistance to tetracycline (100%). L. planetarium showed antibacterial power against B. cereus EMCC1006 reference strain with MIC at 3.1 mg/mL. From the different concentrations (1.5, 3.1, 6.25, 12.5, 25.0, 50.0, 100.0 mg/mL) of L. planetarium which mixed with Kareish cheese and yogurt samples, the minimum concentrations displayed the excellent sensory parameters. TPC and TFC of L. planetarium CFS were 18.5 (μg GAE/g) and 2.67 (μg QE/g), respectively. Regarding antioxidant activity, IC₅₀ of L. planetarium was 53.84 μg/mL, while IC₅₀ of ascorbic acid was 26.36 μg/mL. In sum, L. planetarium could be used as a promising antibacterial and antioxidant agent for biocontrol of B. cereus to ensure dairy safe without negative impact on sensorial attributes.