Antibacterial activity and stability of microencapsulated lemon grass essential oil in feeds for broiler chickens

SUMMARY The antibacterial effect of microencapsulated lemon grass (Cymbopogon citratus) essential oil on strains of Escherichia coli (ATCC8739), Staphylococcus aureus (ATCC 6538) and Salmonella enterica subsp. enterica (ATCC 6017), and the stability of this oil in feeds for broiler chickens were evaluated. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined by the macrodilution method, using the microencapsulated lemon grass essential oil at concentrations of 160 μL mL−1, 80 μL mL−1, 40 μL mL−1, 20 μL mL−1, and 10 μL mL−1. The oil concentration of 80 μL mL−1 presented the best results against the three bacteria evaluated. Samples of 200 g of feed mixed with 120 μL g−1 of the microencapsulated lemon grass essential oil was stored to evaluate the oil stability. Feed without microencapsulated lemon grass essential oil was prepared as control. The oil remained active for seven days, with significant reduction of S. aureus (3.08 CFU), E. coli (3.01 CFU), and S. enterica (3.10 CFU). The microencapsulated lemon grass essential oil at concentration of 80 μL mL−1 had antibacterial effect against the E. coli, S. enterica and S. aureus, and maintained stability of the feed for seven days, even with presence of organic matter, which is source of nutrients for pathogens.

本研究旨在评价微胶囊化香茅（Cymbopogon citratus）精油对大肠埃希菌（Escherichia coli，ATCC8739）、金黄色葡萄球菌（Staphylococcus aureus，ATCC 6538）及肠炎沙门氏菌肠炎亚种（Salmonella enterica subsp. enterica，ATCC 6017）的抗菌活性，并考察该精油在肉鸡饲料中的稳定性。采用宏观稀释法，以160 μL·mL⁻¹、80 μL·mL⁻¹、40 μL·mL⁻¹、20 μL·mL⁻¹及10 μL·mL⁻¹的梯度浓度微胶囊化香茅精油，测定其最低抑菌浓度（Minimum Inhibitory Concentration，MIC）与最低杀菌浓度（Minimum Bactericidal Concentration，MBC）。结果显示，80 μL·mL⁻¹的精油浓度对三种受试菌的抗菌效果最佳。称取200 g饲料，以120 μL·g⁻¹的比例添加微胶囊化香茅精油后储存，以未添加该精油的饲料作为空白对照以考察精油稳定性。实验结果表明，该精油可维持抗菌活性达7天，对金黄色葡萄球菌（菌落数降低3.08 CFU）、大肠埃希菌（菌落数降低3.01 CFU）及肠炎沙门氏菌肠炎亚种（菌落数降低3.10 CFU）均有显著抑制效果。浓度为80 μL·mL⁻¹的微胶囊化香茅精油对上述三种受试菌均具有抗菌作用，且即使在存在病原菌营养源——有机质的条件下，仍可使饲料稳定性维持7天。