Ginsenoside Rb1 is the most abundant ginsenoside in Panax (ginseng). The hydrolysis of this ginsenoside produces compound K, the biologically active ginsenoside of ginseng. We previously identified a fungus Paecilomyces Bainier sp. 229 (sp. 229), which can efficiently convert ginsenoside Rb1 to compound K. In this report, the ginsenoside hydrolyzing beta-glucosidases were isolated from sp. 229 and the pathway of the biotransformation of ginsenoside Rb1 to compound K by sp. 229 was investigated. Based on reverse-phase HPLC and TLC analysis, we found the main metabolic pathway is as follows: ginsenoside Rb1 -> ginsenoside Rd -> ginsenoside F2 -> compound K. Moreover, the results showed that there were other metabolic pathways: ginsenoside Rb1 -> ginsenoside XVII -> ginsenoside F2 -> compound K and ginsenoside Rb1 -> ginsenoside Rg3 -> ginsenoside Rh2. These processes would allow the specific bioconversion of ginsenoside Rb1 to various ginsenosides using an appropriate combination of specific microbial enzymes. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.