To obtain microorganisms for the microbial conversion of ginsenosides in red ginseng powder (RGP). Lactobacillus species (M1-M4 and P1-P4) were isolated from commercial ginseng products. Strain M1 was determined to be L. plantarum by 16S rRNA sequencing. Red ginseng powder (RGP) fermented by L plantarum M1 had a high total content of ginsenosides (142.4 mg/g) as compared to the control (121.8 mg/g). In particular, the ginsenoside metabolites Rg3, Rg5, Rk1, Compound K (CK), Rh1, and Rg2 showed a high level in the fermented RGP (65.5 mg/g) compared to the control (32.7 mg/g). During fermentation for 7 days, total sugar content decreased from 8.55 mg/g to 4 mg/g, uronic acid content reached its maximum (53.43 mu g/g) at 3 days, and total ginsenoside content increased to 176.8 mg/g at 4 days. In addition, ginsenoside metabolites increased from 38.0 mg/g to 83.4 mg/g at 4 days of fermentation. Using everted instestinal sacs of rats, the fermented red ginseng showed a high transport level (10.3 mg of polyphenols/g sac) compared to non-fermented red ginseng (6.67 mg of polyphenols/g sac) after 1 h. These results confirm that fermentation with L plantarum M1 is very useful for preparing minor ginsenoside metabolites while being safe for foods. (C) 2010 Elsevier Ltd. All rights reserved.