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A novel α-L-arabinofuranosidase (Abf22-3) that could biotransform ginsenoside Rc into Rd was obtained from the ginsenoside converting Leuconostoc sp. strain 22-3, isolated from the Korean fermented food kimchi. The gene, termed abf22-3, consisting of 1,527 bp and encoding a protein with a predicted molecular mass of 58,486 Da was cloned into the pMAL-c2x (TEV) vector. A BLAST search using the Abf22-3's amino acid sequence revealed significant homology to that of family 51 glycoside hydrolases. The over-expressed recombinant Abf22-3 in Escherichia coli BL21 (DE3) catalyzed the hydrolysis of the arabinofuranoside moiety attached to the C-20 position of ginsenoside Rc under optimal conditions of pH 6.0 and 30 °C. This result indicated that Abf22-3 selectively converts ginsenoside Rc into Rd, but did not catalyze the hydrolysis of glucopyranosyl groups from Rc or other ginsenosides such as Rb1 and Rb2. Over-expressed recombinant enzymes were purified by two steps with amylose-affinity and DEAE-cellulose chromatography and then characterized. The kinetic parameters for α-L-arabinofuranosidase showed apparent Km and Vmax values of 0.95 ± 0.02 μM and 1.2 ± 0.1 μmol min(-1) mg of protein(-1) against p-nitrophenyl-α-L-arabinofuranoside, respectively. Using a purified MBP-Abf22-3 (10 μg/ml), 0.1 % of ginsenoside Rc was completely converted to ginsenoside Rd within 20 min.

A Gram-positive, aerobic or facultative anaerobic, motile, spore-forming bacterial strain, designated Gsoil 1638T, was isolated from a soil sample of a ginseng field in Pocheon province (South Korea), and was characterized taxonomically by using a polyphasic approach. It grew well on nutrient agar medium, utilized a fairly narrow spectrum of carbon sources and tolerated 10% NaCl. The isolate was positive for catalase and oxidase tests but negative for the degradation of macromolecules such as casein, collagen, starch, chitin, CM-cellulose, xylan and DNA. The G + C content of the genomic DNA was 50.7 mol%. The predominant isoprenoid quinone was menaquinone 7 (MK-7). The major fatty acids were anteiso-C15:0 (44%) and C16:0 (25%). Comparative 16S rRNA gene sequence analysis showed that strain Gsoil 1638T fell within the radiation of the cluster comprising Paenibacillus species and joined Paenibacillus anaericanus DSM 15890T with a bootstrap value of 100%. These two strains shared 99.5% 16S rRNA gene sequence similarity with each other. The phylogenetic distance from any other validly described species within the genus Paenibacillus was less than 96.2%. DNA–DNA relatedness value between strain Gsoil 1638T and its closest phylogenetic neighbor, Paenibacillus anaericanus, was 62%. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain Gsoil 1638T (= KCTC 13931T = LMG 23406T = CCUG 52472T) was classified in the genus Paenibacillus as the type strain of a novel species, for which the name Paenibacillus ginsengisoli sp. nov. is proposed.

Biotransformation of ginsenosides was examined using lactic acid bacteria isolated from several kinds of kimchi. A Gram-positive, facultatively anaerobic, non-motile, non-spore-forming, and rod-shaped lactic acid bacterial strain, designated EMML 3041(T), was determined to have ginsenoside-converting activity and its taxonomic position was investigated using a polyphasic approach. Strain EMML 3041(T) displayed β-glucosidase activity that was responsible for its ability to transform ginsenoside Rb1 (one of the dominant active components of ginseng) to F2 via gypenoside XVII, ginsenoside Rb2 to compound Y via compound O, ginsenoside Rc to compound Mc via compound Mc1, and ginsenoside Rd to ginsenoside F2. On the basis of the 16S rRNA gene sequence similarity, strain EMML 3041(T) was shown to belong to the genus Lactobacillus and is closely related to Lactobacillus versmoldensis KU-3(T) (98.3 % sequence similarity). Polyphasic taxonomy study confirmed that the strain EMML 3041(T) represents a novel species, for which the name Lactobacillus ginsenosidimutans sp. nov. is proposed, with EMML 3041(T) (=KACC 14527(T) = JCM 16719(T)) as the type strain.