Yong-Seob Jeong

Bioconversion of cellulose into ethanol by nonisothermal simultaneous saccharification and fermentation

The kinetic characteristics of cellulase and β-glucosidase during hydrolysis were determined. The kinetic parameters were found to reproduce experimental data satisfactorily and could be used in a simultaneous saccharification and fermentation (SSF) system by coupling with a fermentation model. The effects of temperature on yeast growth and ethanol production were investigated in batch cultures. In the range of 35–45°C, using a mathematical model and a computer simulation package, the kinetic parameters at each temperature were estimated. The appropriate forms of the model equation for the SSF considering the effects of temperature were developed, and the temperature profile for maximizing the ethanol production was also obtained. Briefly, the optimum temperature profile began at a low temperature of 35°C, which allows the propagation of cells. Up to 10 h, the operating temperature increased rapidly to 39°C, and then decreased slowly to 36°C. In this nonisothermal SSF system with the above temperature profile, a maximum ethanol production of 14.87 g/L was obtained.

Platycosides from the Roots of Platycodon grandiflorum and Their Health Benefits

The extracts and pure saponins from the roots of Platycodon grandiflorum (PG) are reported to have a wide range of health benefits. Platycosides (saponins) from the roots of PG are characterized by a structure containing a triterpenoid aglycone and two sugar chains. Saponins are of commercial significance, and their applications are increasing with increasing evidence of their health benefits. The biological effects of saponins include cytotoxic effects against cancer cells, neuroprotective activity, antiviral activity, and cholesterol lowering effects. Saponins with commercial value range from crude plant extracts, which can be used for their foaming properties, to high purity saponins such as platycodin D, which can be used for its health applications (e.g., as a vaccine adjuvant). This review reveals that platycosides have many health benefits and have the potential to be used as a remedy against many of the major health hazards (e.g., cancer, obesity, alzheimer’s) faced by populations around the world. Methods of platycoside purification and analysis are also covered in this review.

Inhibitory Effect of Cinnamon Essential Oils on Selected Cheese-contaminating Fungi (Penicillium spp.) during the Cheese-ripening Process

The antifungal effects of essential oils (EOs) on cultures of the known cheese fungal contaminants Penicillium spp. were evaluated. Cinnamon leaf and bark EOs were the most effective among 8 EOs tested. The main components of both cinnamon EOs were eugenol, cinnamaldehyde, and linalool. Both inhibited growth of Penicillium spp. at a concentration of 10% v/v (2,000 ppm/mm2) on a lawn cell plate. When tested using 3 commercially available cheese starters, cinnamon EOs showed no effect against the FD-DVS ABT-5 cheese starter. However, growth of lactobacilli was inhibited in the presence of ≥10% (v/v) of leaf and bark EOs for the KAZU 1 starter, and ≥5% (v/v) for the FD-DVS FLORA-DANICA starter. A concentration of 4,000 ppm/mm2 of cinnamon EOs completely inhibited growth of the Penicillium spp. that naturally contaminates the surface of Appenzeller cheese.

Bioconversion of cellulose to ethanol by the temperature optimized simultaneous saccharification and fermentation

The objectives of this study are to develop a set of equations that include the temperature effect, to predict the ethanol production in SSF process at a optimum temperature profile by using numerical parameters obatined, and to test the validity of the approach by comparing the predicted values with typical experimental results

Development of Miniaturized Culture Systems for Large Screening of Mycelial Fungal Cells of Aspergillus terreus Producing Itaconic Acid

The task of improving a fungal strain is highly time-consuming due to the requirement of a large number of flasks in order to obtain a library with enough diversity. In addition, fermentations (particularly those for fungal cells) are typically performed in high-volume (100-250 ml) shake-flasks. In this study, for large and rapid screening of itaconic acid (IA) high-yielding mutants of Aspergillus terreus, a miniaturized culture method was developed using 12-well and 24-well microtiter plates (MTPs, working volume = 1-2 ml). These miniaturized MTP fermentations were successful, only when highly filamentous forms were induced in the growth cultures. Under these conditions, loose-pelleted morphologies of optimum sizes (less than 0.5 mm in diameter) were casually induced in the MTP production cultures, which turned out to be the prerequisite for the active IA biosynthesis by the mutated strains in the miniaturized fermentations. Another crucial factor for successful MTP fermentation was to supply an optimal amount of dissolved oxygen into the fermentation broth through increasing the agitation speed (240 rpm) and reducing the working volume (1 ml) of each 24-well microtiter plate. Notably, almost identical fermentation physiologies resulted in the 250 ml shake-flasks, as well as in the 12-well and 24-well MTP cultures conducted under the respective optimum conditions, as expressed in terms of the distribution of IA productivity of each mutant. These results reveal that MTP cultures could be considered as viable alternatives for the labor-intensive shake-flask fermentations even for filamentous fungal cells, leading to the rapid development of IA high-yield mutant strains.

Lactobacillus plantarum-mediated conversion of flavonoid glycosides into flavonols, quercetin, and kaempferol in Cudrania tricuspidata leaves

High value-added food materials were developed based on enhancement of phenolic contents in Cudrania tricuspidata leaves using fermentation of silkworm thorn leaves with Lactobacillus derived from Korean soybean paste. Ethanol extracts from fermentates were examined for antioxidant activities and flavonoid and corresponding glycoside contents. Radical scavenging activities were increased by approximately 20% after fermentation. Two prominent spectral peaks in fermentates that increased in size, compared with non-fermentates, were identified as quercetin (m/z 301.1) and kaempferol (m/z 285.3). Three peaks that decreased in size in fermentates were identified as quercetin-7-O-beta-glucopyranoside (m/z 463.1), kaempferol-3-O-beta-glucopyranoside (m/z 447.1), and kaempferol-7-O-beta-glucopyranoside (m/z 447.2). Conversion of flavonoid glycosides to flavonols, quercetin and kaempferol, occurred in silkworm thorn leaves due to fermentation with Lactobacillus.

Lactic acid bacteria-mediated fermentation of Cudrania tricuspidata leaf extract improves its antioxidative activity, osteogenic effects, and anti-adipogenic effects

The goal of this study was to assess the potential of fermented Cudrania tricuspidata leaf (CTL) aqueous extract as a functional food material. The CTL aqueous extract was fermented using lactic acid bacteria (LAB) isolated from soybean-fermented foods and the biological effects of the resultant fermented extracts on MG-63 human osteoblastic cells and 3T3-L1 mouse pre adipocytes were examined in vitro. We found that (1) the radical scavenging activities of CTL extracts fermented by various LAB strains (fermented CTL, F-CTL) were ~2- fold higher than that of non-fermented CTL extract (NFCTL), (2) F-CTL extract enhanced MG-63 cell proliferation compared to NF-CTL-treated cells, (3) the level of alkaline phosphatase activity in F-CTL-treated MG-63 cells was significantly higher than that in NF-CTL-treated cells, and (4) 3T3-L1 cell differentiation was dramatically decreased by F-CTL treatment, but not by NF-CTL. These findings suggest that CTL that has undergone LAB-mediated fermentation may be beneficial for promoting osteogenic differentiation of osteoblastic cells and inhibiting fat accumulation in adipocytes.

Optimization of cultivation medium and fermentation parameters for lincomycin production by Streptomyces lincolnensis

Production of lincomycin by Streptomyces lincolnensis was studied by varying medium composition and environmental conditions. With the medium composition optimized by statistical experimental design (45 g/L soluble starch, 15 g/L sugar cane molasses, 13.33 g/L peptone water, 6.67 g/L NaNO3 and 4.0 g/L CaCO3), lincomycin production increased by 2 ∼ 3 fold compared to that obtained with un-optimized basal medium. Lincomycin production was further improved by optimizing culture conditions such as agitation speed, impeller type and pH under the optimized medium condition. The highest titer of 350 mg/L lincomycin was achieved from 240 h bioreactor culture. These results demonstrate that fermentation conditions for maximal lincomycin production by Streptomyces lincolnensis were optimized via biotechnological processes.

Enhancement of 1-deoxynojirimycin content and α-glucosidase inhibitory activity in mulberry leaf using various fermenting microorganisms isolated from Korean traditional fermented food

Mulberry leaf is known to be effective in inhibiting increases in blood glucose levels in diabetic patients. 1-Deoxynojirimycin (DNJ), a α-glucosidase inhibitor, is the major effective component in mulberry leaf. The aim of this study was to evaluate the level of DNJ in mulberry leaves fermented by various microorganisms, including lactic acid bacteria, yeast, and the bacillus isolated from Korean traditional fermented soybean food, and to assess the inhibitory effect of fermented mulberry leaf powder extract (FMLE) on α-glucosidase activity. The DNJ content in unfermented mulberry leaf powder extract (UFMLE), the control, was determined to be 53.2 ± 1.5 mg/100 g (dry weight eq.). Lactobacillus plantarum, Zygosaccharomyces rouxii, Wickerhamomyces anomalus, and Bacillus subtilis remarkably increased the DNJ levels in mulberry leaves by 1.2, 1.5, 2.0, and 1.8-fold, respectively, compared to the control. The inhibitory effects of the FMLEs on α-glucosidase were also examined at various concentrations, and their α-glucosidase inhibitory effects tended to be higher than that in UFMLE. These findings suggest that Korean traditional fermenting microorganisms can be used as starter strains for the development of DNJ-enhanced food products, and that FMLEs have the potential to be used in various functional foods for the prevention of diabetes.

Multipotent adult hippocampal progenitor cells maintained as neurospheres favor differentiation toward glial lineages

Adult hippocampal progenitor cells (AHPCs) are generally maintained as a dispersed monolayer population of multipotent neural progenitors. To better understand cell-cell interactions among neural progenitors and their influences on cellular characteristics, we generated free-floating cellular aggregates, or neurospheres, from the adherent monolayer population of AHPCs. Results from in vitro analyses demonstrated that both populations of AHPCs were highly proliferative under maintenance conditions, but AHPCs formed in neurospheres favored differentiation along a glial lineage and displayed greater migrational activity than the traditionally cultured AHPCs. To study the plasticity of AHPCs from both populations in vivo, we transplanted green fluorescent protein (GFP)-expressing AHPCs via intraocular injection into the developing rat eyes. Both AHPC populations were capable of surviving and integrating into developing host central nervous system, but considerably more GFP-positive cells were observed in the retinas transplanted with neurosphere AHPCs, compared to adherent AHPCs. These results suggest that the culture configuration during maintenance for neural progenitor cells (NPCs) influences cell fate and motility in vitro as well as in vivo. Our findings have implication for understanding different cellular characteristics of NPCs according to distinct intercellular architectures and for developing cell-based therapeutic strategies using lineage-committed NPCs.