title: Inactivation of Bacillus subtilis spores by high pressure CO2 with high temperature.
abstract: The objective of this study was to investigate the inactivation of the Bacillus subtilis spores by high pressure CO2 combined with high temperature (HPCD+HT) and to analyze the clumping effect of the spores on their HPCD+HT resistance. The spores of B. subtilis were subjected to heat at 0.1 MPa and HPCD at 6.5-25 MPa, and 82 °C, 86 °C, and 91 °C for 0-120 min. The spores were effectively inactivated by HPCD+HT, but a protective effect on the spores was also found, which was closely correlated to the pressure, temperature and time. The spores treated by HPCD+HT at 6.5 and 10 MPa exhibited a two-stage inactivation curve of shoulder and log-linear regions whereas the spores at 15-25 MPa exhibited a three-stage inactivation curve of shoulder, log-linear and tailing regions, and these curves were well fitted to the Geeraerd model. Approximately 90% of pyridine-2,6-dicarboxylic acid (DPA) was released after HPCD+HT and the 90% DPA release time depend on the pressure and temperature. Moreover, the spore clumping in suspensions was examined by dynamic light scattering. The particle size of the spore suspensions increased with the increase of pressure, temperature and time, indicating the spore clumping. 0.1% Tween 80 as a surfactant inhibited the spore clumping and increased the inactivation ratio of the spores by HPCD+HT. These results indicated that the spore clumping enhanced the spores' resistance to HPCD+HT and induced a protective effect.
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, National Engineering Research Centre for Fruit and Vegetable Processing, Key Lab of Fruit and Vegetable Processing, Ministry of Agriculture, Beijing 100083, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Rao
authors.affiliation: Institute of Quality Standard & Testing Technology for Agro-Products, Chinese Academy of Agricultural Sciences, Key Laboratory of Agro-Food Safety and Quality, Ministry of Agriculture, Beijing 100081, China.
authors.forename: Zhenzhen
authors.initials: Z
authors.lastname: Xu
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, National Engineering Research Centre for Fruit and Vegetable Processing, Key Lab of Fruit and Vegetable Processing, Ministry of Agriculture, Beijing 100083, China.
authors.forename: Yongtao
authors.initials: Y
authors.lastname: Wang
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, National Engineering Research Centre for Fruit and Vegetable Processing, Key Lab of Fruit and Vegetable Processing, Ministry of Agriculture, Beijing 100083, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhao
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, National Engineering Research Centre for Fruit and Vegetable Processing, Key Lab of Fruit and Vegetable Processing, Ministry of Agriculture, Beijing 100083, China.
authors.forename: Xiaosong
authors.initials: X
authors.lastname: Hu
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, National Engineering Research Centre for Fruit and Vegetable Processing, Key Lab of Fruit and Vegetable Processing, Ministry of Agriculture, Beijing 100083, China. Electronic address: liaoxjun@hotmail.com.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Liao
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects*; D002462:Cell Membrane / Q000187:drug effects; D006358:Hot Temperature; D050296:Microbial Viability / Q000187:drug effects; D010848:Picolinic Acids / Q000378:metabolism; D011312:Pressure; D013171:Spores, Bacterial / Q000187:drug effects*; D013501:Surface-Active Agents / Q000494:pharmacology
chemical_list: D010848:Picolinic Acids; D013501:Surface-Active Agents; C004860:dipicolinic acid
keywords: Bacillus subtilis; Clumping; High pressure CO(2); Inactivation kinetics; Protective effect; Spore