Pressure-induced thermotolerance of Lactobacillus rhamnosus GG

Non-lethal high pressure treatment was evaluated regarding its potential of inducing heat resistance in Lactobacillus rhamnosus GG. Pressure pre-treated cells (at 100 MPa and 37 °C for 10 min) showed higher survivability than untreated ones when both were heat treated at 60 °C. Upon exposure to this lethal temperature for 5 min, cells survived better by 1.5 log-cycles in comparison to control group, when they were previously pressure treated at 100 MPa and 37 °C for 10 min. Apparently, only short-time heat resistance was positively affected by such pressure pre-conditioning step since at prolonged holding time at 60 °C (more than 7 min), no significant differences regarding the inactivation rate was observed. Various pressures (100–200 MPa), temperatures (37–50 °C), and holding times (5–10 min) were systematically investigated. The findings can serve as indications towards optimizing production of probiotic starter cultures using spray-drying.