2.6.1. Preparation of P. acnes suspension
P. acnes was grown in 1% glucose BHI for 72 h at 37 °C in anaerobic atmosphere. The log phase bacterial culture
was harvested, washed thrice in phosphate buffered saline (PBS, pH 7.2), and incubated at 80 °C for 30 min to heat-kill
the bacteria. The heat-killed P. acnes suspension was stored at 4 °C until use.