Seong-Eun Park

Biotransformation of major ginsenosides in ginsenoside model culture by lactic acid bacteria

Background Some differences have been reported in the biotransformation of ginsenosides, probably due to the types of materials used such as ginseng, enzymes, and microorganisms. Moreover, most microorganisms used for transforming ginsenosides do not meet food-grade standards. We investigated the statistical conversion rate of major ginsenosides in ginsenosides model culture during fermentation by lactic acid bacteria (LAB) to estimate possible pathways. Methods Ginsenosides standard mix was used as a model culture to facilitate clear identification of the metabolic changes. Changes in eight ginsenosides (Rb1, Rb2, Rc, Rd, Re, Rf, Rg1, and Rg2) during fermentation with six strains of LAB were investigated. Results In most cases, the residual ginsenoside level decreased by 5.9–36.8% compared with the initial ginsenoside level. Ginsenosides Rb1, Rb2, Rc, and Re continuously decreased during fermentation. By contrast, Rd was maintained or slightly increased after 1 d of fermentation. Rg1 and Rg2 reached their lowest values after 1–2 d of fermentation, and then began to increase gradually. The conversion of Rd, Rg1, and Rg2 into smaller deglycosylated forms was more rapid than that of Rd from Rb1, Rb2, and Rc, as well as that of Rg1 and Rg2 from Re during the first 2 d of fermentation with LAB. Conclusion Ginsenosides Rb1, Rb2, Rc, and Re continuously decreased, whereas ginsenosides Rd, Rg1, and Rg2 increased after 1–2 d of fermentation. This study may provide new insights into the metabolism of ginsenosides and can clarify the metabolic changes in ginsenosides biotransformed by LAB.

Metabolite profiling of fermented ginseng extracts by gas chromatography mass spectrometry

Background Ginseng contains many small metabolites such as amino acids, fatty acids, carbohydrates, and ginsenosides. However, little is known about the relationships between microorganisms and metabolites during the entire ginseng fermentation process. We investigated metabolic changes during ginseng fermentation according to the inoculation of food-compatible microorganisms. Methods Gas chromatography mass spectrometry (GC-MS) datasets coupled with the multivariate statistical method for the purpose of latent-information extraction and sample classification were used for the evaluation of ginseng fermentation. Four different starter cultures (Saccharomyces bayanus, Bacillus subtilis, Lactobacillus plantarum, and Leuconostoc mesenteroide) were used for the ginseng extract fermentation. Results The principal component analysis score plot and heat map showed a clear separation between ginseng extracts fermented with S. bayanus and other strains. The highest levels of fructose, maltose, and galactose in the ginseng extracts were found in ginseng extracts fermented with B. subtilis. The levels of succinic acid and malic acid in the ginseng extract fermented with S. bayanus as well as the levels of lactic acid, malonic acid, and hydroxypruvic acid in the ginseng extract fermented with lactic acid bacteria (L. plantarum and L. mesenteroide) were the highest. In the results of taste features analysis using an electronic tongue, the ginseng extracts fermented with lactic acid bacteria were significantly distinguished from other groups by a high index of sour taste probably due to high lactic acid contents. Conclusion These results suggest that a metabolomics approach based on GC-MS can be a useful tool to understand ginseng fermentation and evaluate the fermentative characteristics of starter cultures.

A GC-MS based metabolomics approach to determine the effect of salinity on Kimchi

GC-MS datasets coupled with multivariate statistical analysis were used to investigate metabolic changes in Kimchi during fermentation and metabolic differences in Kimchi added with various amounts (0, 1.25, 2.5, and 5%) of salts. PCA score plot obtained after 1day of fermentation were clearly distinguishable by different salinity groups, implying that early fermentation speed varied according to Kimchi salinity. PLS-DA score plot from data obtained on the 50th day of fermentation also showed a clear separation, indicating metabolites of Kimchi were different according to salinity. Concentrations of lactic acid, acetic acid, and xylitol were the highest in Kimchi with 5% salinity while concentration of fumaric acid was the highest in Kimchi with 0% salinity. Rarefaction curves showed that numbers of operational taxonomic units (OTUs) in Kimchi with 5% salinity were higher than those in Kimchi with 0% salinity, implying that Kimchi with 5% salinity had more bacterial diversities. This study highlights the applicability of GC-MS based metabolomics for evaluating fermentative characteristics of Kimchi with different salinities.

Effectiveness of Yeast Nutrients on Stuck Fermentation of Blueberry Wine

In this study, we investigated the effect of various yeast nutrients on stuck and sluggish fermentation of blueberry wine. Sugar consumption rates during fermentation were observed after the addition of yeast extract, diammonium phosphate, yeast energizer, raisin, or banana to fermenting blueberry wine. After fermentation, the alcohol concentrations of wines containing yeast extract (14.1%) and banana (13.3%) were higher than those of wines containing diammonium phosphate (12.6%), yeast energizer (12.4%), and raisin (11.4%). Correspondingly, levels of soluble solids were lower in wines to which yeast extract (3.9 o Bx) and banana (2.5 o Bx) were added than in wines to which diammonium phosphate (4.6 o Bx), yeast energizer (4.6 o Bx), and raisin (6.3 o Bx) were added. Thus, we concluded that banana could be

GC–MS based metabolomics study of fermented stipe of Sparassis crispa

GC–MS coupled with multivariate statistical analysis was performed to understand metabolites difference between pileus and stipe of Sparassis crispa (cauliflower mushroom). Metabolic changes of S. crispa after fermentation by different microorganisms were also investigated. PCA score plot showed a clear separation between pileus and stipe of S. crispa regardless of fermentation. However, OPLS-DA score plot showed clear separation among fermented S. crispa samples according to microbial strain used, indicating that both pileus and stipe fermented with the same strain showed similar pattern of metabolites. Fructose, lactic acid, citric acid, malic acid, and phosphoric acid were metabolites that contributed to the discrimination of fermented S. crispa samples. Results of this study provide novel insights into intrinsic characteristics of stipe of S. crispa which is cheaper than pileus as ingredient for alternative functional food.

Quality characteristics of fermented sausage prepared with soy sauce

The contributions of soy sauce to the quality characteristics of fermented sausages were investigated. The number of lactic acid bacteria in sausages prepared with soy sauce increased from the first day of fermentation, and the population reached approximately log 7 CFU/g by the 5th day of fermentation. The pH decreased sharply to 5.0-5.1 by the 5th day of fermentation, in accordance with the dramatic increase of titratable acidity. After 36 days of fermentation, the levels of total organic acids and amino acids in soy sauce sausages increased to 3,026.3-3,116.4 mg/100 g and 1,132.2-1,172.8 mg/100 g respectively, and this level was even higher than those of the sausage fermented with a starter culture. 2% soy sauce sausage also showed higher values of hardness, chewiness, and smoke odor than the control. These results suggest that soy sauce has great potential as an alternative starter culture and additive for the quality improvement of fermented sausages.

A GC-MS based metabolic profiling of fermented sausage supplemented with pineapple

A GC-MS based metabolomic study was performed to understand metabolic changes during sausage fermentation and to investigate how the incorporation of pineapple affects the metabolic profiles of fermented sausages. Principal component analysis models showed clear metabolic differences among the fermented sausages according to the fermentation periods and the pineapple addition. Increased amounts of amino acids and organic acids except for citric acid, along with decreased levels of sugars were observed after fermentation. Higher levels of sugars and citric acid in the pineapple supplemented sausages dramatically decreased during the early stage of fermentation. The contents of lactic acid, phosphoric acid, succinic acid, ribonic acid, valine, leucine, isoleucine, glycine, threonine, glutamic acid, glucose, and sucrose were significantly increased in the 2% pineapple addition sausages. GC-MS and PCA analytical methods provide a new approach to understand of the metabolic changes in fermented sausages during fermentation.