Antcin K is one of the major ergostane triterpenoids from the fruiting bodies of Antrodia cinnamomea, a parasitic fungus that grows only on the inner heartwood wall of the aromatic tree Cinnamomum kanehirai Hay (Lauraceae). To search for strains that have the ability to biotransform antcin K, a total of 4311 strains of soil bacteria were isolated, and their abilities to catalyze antcin K were determined by ultra-performance liquid chromatography analysis. One positive strain, AK 1817, was selected for functional studies. The strain was identified as Psychrobacillus sp., based on the DNA sequences of the 16S rRNA gene. The biotransformation metabolites were purified with the preparative high-performance liquid chromatography method and identified as antcamphin E and antcamphin F, respectively, based on the mass and nuclear magnetic resonance spectral data. The present study is the first to report the biotransformation of triterpenoids from A. cinnamomea (Antrodia cinnamomea).