Ultrasound pretreatment enhances the inhibitory effects of nisin/carvacrol against germination, outgrowth and vegetative growth of spores of Bacillus subtilis ATCC6633 in laboratory medium and milk: Population and single-cell analysis

• Published in: International journal of food microbiology 2019-12, Vol.311, p.108329-108329, Article 108329
• Main Authors: Fan, Lihua, Ismail, Balarabe Bilyaminu, Hou, Furong, Muhammad, Aliyu Idris, Ding, Tian, Liu, Donghong
• Format: Article
• Language: English
• Subjects: Animals; Bacillus subtilis; Bacillus subtilis - growth & development; Carvacrol; Cymenes - pharmacology; Drug Synergism; Flow cytometry; Food medium; Germination; Inhibition; Laboratories; Milk; Milk - microbiology; Natural antimicrobials; Nisin; Nisin - pharmacology; Pretreatment; Single-Cell Analysis; Spore germination; Spores; Spores, Bacterial - growth & development; Sporulation; Ultrasonic imaging; Ultrasound; Vegetative cells
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2019.108329

This study evaluated the synergetic inhibitory effects of ultrasound and nisin/carvacrol on spore germination, outgrowth, and subsequent growth of vegetative cell of Bacillus subtilis in laboratory medium and milk. Ultrasound pretreatment (3.33 W/mL, 15 min) and nisin/carvacrol (0.01%, 0.02%) synergistically inhibited spore germination, outgrowth, and vegetative growth of spores in laboratory medium. Whereas no such inhibitory effect was observed in milk even with a 10-fold increase in the concentration (1%) of nisin. Flow cytometry analysis showed that the germination capacities of ultrasound pretreated spores combined with nisin/carvacrol (67.3% and 30.5%, respectively) was lower than that of the untreated spores (95.1%). These results quantitatively revealed the inhibitory effect of the combined treatments which were confirmed by phase-bright spore observations at single cell level. In general, the current work identified the combined ultrasound-carvacrol treatment as an effective strategy to control spores and vegetative cells of B. subtilis in the laboratory medium and milk during abusive storage. •Synergism of ultrasound and nisin/carvacrol demonstrated in laboratory medium.•Spores stressed with the combined treatments were more heterogeneously.•The combined treatments could control B. subtilis in milk better than individual treatment.