• Microbiology and Biotechnology Letters
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• v.49 no.3
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• pp.320-328
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• 2021

High GABA-enriched yeast extract, for various nutritionally and pharmaceutically important functional foods, was prepared using a novel isolate of Debaryomyces hansenii JBCC541. Under optimized conditions, GABA conversion rates are significantly enhanced up to 7.55 g/l by D. hansenii JBCC541, increasing their synthesis yield 40 times. The total amino acid content of the prepared yeast extract was 10733.86 mg/l (257.36 mg/g), consisting of alanine, lysine, glutamine, leucine, and valine as the primary amino acids. The GABA content was significantly enhanced up to 6790 mg/l (162.80 mg/g) in the presence of glutamic acid, with approximately 10-fold higher GABA production. Flavor amino acids were also highly enhanced, indicating that the prepared yeast extract might be useful for preparing various functional and sensuous foods. Our results were promising as a GABA-enriched yeast extract preparation tool ensuring a suitable food material level with the potential for functionally enhanced food industrial applications.

• Microbiology and Biotechnology Letters
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• v.37 no.2
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• pp.140-146
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• 2009

Cyclosporin, an immunosuppressant, is a representative group of biologically active secondary metabolites produced by the fungus Tolypocladium inflatum. The amount and ratio of cyclosporin derivatives in the culture broth are an important factors for the production of cyclosporin A and the purification in the industrial process. Therefore, we studied the effect of amino acids and complex organic nitrogen sources using Tolypocladium inflatum mutants on the productivity of cyclosporin A and the ratio of cyclosporin derivatives. Overproducing mutant YHC-004 having seven times higher productivity than mother strain's could be obtained through the artificial mutation by UV irradiation. The concentration and kind of organic nitrogens and amino acids shows the profound effect on the productivity of cyclosporin A and ratio of cyclosporin derivatives. As a result, it was possible to raise the productivity and the ratio of cyclosporin A up to 3,430 mg/L and 93% respectively, but on the other hand the other cyclosporin derivatives decreased less than 2% in the culture broth.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.5
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• pp.756-762
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• 2014

This study evaluated the quality characteristics of soybean fermented with several Bacillus sp., which were selected based on their high enzymatic and antimicrobial activities. Total aerobic bacterial counts of fermented soybeans with HJ5-2 ($3.00{\times}10^9CFU/mL$) were the highest among all strains. Lactic acid bacteria numbered $2.50{\times}10^2{\sim}7.30{\times}10^4CFU/mL$ in soybeans fermented with isolates. Amylase and protease activities of the RD7-7 sample were the highest among all strains. Reducing sugar and amino-type nitrogen contents of fermented soybeans with HJ18-4 (2.35%) and RD7-7 (227.96 mg%) were the highest. Total amino acid contents of the samples were 16.62~18.38%, and glutamic acid, aspartic acid, leucine, lysine, arginine were major amino acids. Oxalic acid (36.51~63.57 mg/100 g) and succinic acid (429.49~600.15 mg/100 g) were the predominant organic acid. These results provide useful information for development starter (single and complex) as well as for the production of high quality fermented soybean foods.

• Korean Journal of Food Science and Technology
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• v.4 no.2
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• pp.123-133
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• 1972

Over 90 of lysine producing auxotrophs were obtained from Corynebacterium sp. S-27-12, Brevibacterium flavum ATCC 15168 and Micrococcus glutamicus ATCC 13032 by UV light, $Co^{60}$ irradiation and N-methyl-N'-nitro-N-nitrosoguanidine treatment. One of the mutant, Brev. flavum U46-N59, was identified as a leucine auxotroph and accumulated lysine during flask (500 ml) cultivation (180 strokes/min.) up to 21.6 mg per ml of broth at pH 7.5 and $28^{\circ}C$ after 4 days. The medium consisted of glucose, 100; urea, 10; corn steep liquor, 40; $KH_2PO_4,\;2;\;K_2HPO_4,\;0.5;\; MgSO_4.\;7H_2O,\;0.4;\;antifoam\;S-57,\;1g;\;Fe_2(SO_4)_3.XH-2O,\;10;\; MnCl_2,\;4H_2O,\;10mg;\;biotin,\;30;\;thiamine-HCl,\;100{\mu}g$in 1l of distilled water, and 40 U/ml of penicillin was added after 36 hrs fermentation.

• 한국균학회소식:학술대회논문집
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• 2016.05a
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• pp.27-27
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• 2016

The ascomycete fungus Fusarium graminearum is the most common pathogen of Fusarium head blight (FHB), a devastating disease for major cereal crops worldwide. FHB causes significant crop losses by reducing grain yield and quality as well as contaminating cereals with trichothecenes and zearalenone (ZEA) that pose a serious threat to animal health and food safety. ZEA is a causative agent of hyperestrogenic syndrome in mammals and can result in reproductive disorders in farm animals. In F. graminearum, the ZEA biosynthetic cluster is composed of four genes, PKS4, PKS13, ZEB1, and ZEB2, which encode a reducing polyketide synthase, a nonreducing polyketide synthase, an isoamyl alcohol oxidase, and a transcription factor, respectively. Although it is known that ZEB2 primarily acts as a regulator of ZEA biosynthetic cluster genes, the mechanism underlying this regulation remains undetermined. In this study, two isoforms (ZEB2L and ZEB2S) from the ZEB2 gene in F. graminearum were characterized. It was revealed that ZEB2L contains a basic leucine zipper (bZIP) DNA-binding domain at the N-terminus, whereas ZEB2S is an N-terminally truncated form of ZEB2L that lacks the bZIP domain. Interestingly, ZEA triggered the induction of both ZEB2L and ZEB2S transcription. In ZEA producing condition, the expression of ZEB2S transcripts via alternative promoter usage was directly or indirectly initiated by ZEA. Physical interaction between ZEB2L and ZEB2L as well as between ZEB2L and ZEB2S was observed in the nucleus. The ZEB2S-ZEB2S interaction was detected in both the cytosol and the nucleus. ZEB2L-ZEB2L oligomers activated ZEA biosynthetic cluster genes, including ZEB2L. ZEB2S inhibited ZEB2L transcription by forming ZEB2L-ZEB2S heterodimers, which reduced the DNA-binding activity of ZEB2L. This study provides insight into the autoregulation of ZEB2 expression by alternative promoter usage and a feedback loop during ZEA production.

• Journal of Microbiology and Biotechnology
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• v.31 no.7
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• pp.949-955
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• 2021

Previously, our research group isolated Bifidobacterium breve IDCC4401 from infant feces as a potential probiotic. For this study, we evaluated the safety of B. breve IDCC4401 using genomic and phenotypic analyses. Whole genome sequencing was performed to identify genomic characteristics and investigate the potential presence of genes encoding virulence, antibiotic resistance, and mobile genetic elements. Phenotypic analyses including antibiotic susceptibility, enzyme activity, production of biogenic amines (BAs), and proportion of D-/L-lactate were evaluated using E-test, API ZYM test, high-performance liquid chromatography (HPLC), and D-/L-lactic acid assay respectively. The genome of B. breve IDCC4401 consists of 2,426,499 bp with a GC content of 58.70% and 2,016 coding regions. Confirmation of the genome as B. breve was provided by its 98.93% similarity with B. breve DSM20213. Furthermore, B. breve IDCC4401 genes encoding virulence and antibiotic resistance were not identified. Although B. breve IDCC4401 showed antibiotic resistance against vancomycin, we confirmed that this was an intrinsic feature since the antibiotic resistance gene was not present. B. breve IDCC4401 showed leucine arylamidase, cystine arylamidase, α-galactosidase, β-galactosidase, and α-glucosidase activities, whereas it did not show production of harmful enzymes such as β-glucosidase and β-glucuronidase. In addition, B. breve IDCC4401 did not produce any tyramine, histamine, putrescine, cadaverine, or 2-phenethylamine, which are frequently detected BAs during fermentation. B. breve IDCC4401 produced 95.08% of L-lactate and 4.92% of D-lactate. Therefore, our findings demonstrate the safety of B. breve IDCC 4401 as a potential probiotic for use in the food industry.

• Microbiology and Biotechnology Letters
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• v.17 no.6
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• pp.556-562
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• 1989

The bioconversion of mandarin orange peel press liquor to single cell protein (SCP) by two yeast strains, F-60, and C-7, which were isolated from mandarin orange peel was carried out and compared with that of using Candida utilis IFO 0598. Experiments were directed toward the high yield of biomass and high protein in cultures of the strains mentioned above. Candida utilis IFO 0598, F-60 and C-7 strains were cultivated at 3$0^{\circ}C$, pH 5.2 for 3 days in shaking flasks. The effects of some nutrients on cell growth were studied. Cell mass and protein content per cell mass were increased by addition of urea 1%, KH$_2$PO$_4$ 0.1% and MgSO$_4$ㆍ7$H_2O$ 0.05%, When the F-60 strain cultured under the optimal conditions, cell mass, growth yield and protein content were 41.2g/l, 53.9%, 59.7%, respectively. Cell mass was also increased up to 15% by modifying the fermentation condition on the bench type 20l jar fermentor. Crude fat content (10.3%) of dried C-7 cell was higher than those of C. utilis and F-60, 4.9% and 5.6% respectively. Total protein content of the F-60 strain was 59.7% per dry weight. And we compared their amino acid compositions with that of FAO provisional pattern. In the case of the F-60 strains, amino acid contents such as lysine, leucine and isoleucine were much higher than those of methionine, cystine and tryptophan.

• Journal of Microbiology and Biotechnology
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• v.22 no.11
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• pp.1518-1522
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• 2012

Leuconostoc mesenteroides is a heterofermentative Grampositive bacterium that plays key roles in fermentation of foods such as kimchi, sauerkraut, and milk, leading to the production of various organic acids and aromatic compounds. To study the microbiological and genomic characteristics of L. mesenteroides, we have developed a new chemically defined minimal medium by using the single omission technique. During the exponential cell growth, this species required glutamine, methionine, valine, and nicotinic acid as essential nutrients and 8 amino acids (arginine, cysteine, histidine, leucine, phenylalanine, proline, threonine, and tryptophan), 5 vitamins (ascorbic acid, folic acid, inosine, calcium panthothenate, and thiamine), and others (manganese, magnesium, adenine, uracil, and Tween 80) as supplemental nutrients. This medium is useful to study the metabolic characteristics of L. mesenteroides and to explain its role in food fermentation.

• Journal of Marine Bioscience and Biotechnology
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• v.10 no.1
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• pp.18-25
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• 2018

Chlorella is quantitatively and qualitatively high in protein with balanced essential amino acid profiles, vitamins and minerals. ${\gamma}-Aminobutyric$ acid (GABA) is broadly distributed in nature and fulfills multi-physiological functions including effect such as a health-promoting functional compound. To improve the GABA production, Chlorella protothecoides were grown through the modified mixtrophic culture medium containing 2L of sterilized bristol medium with 0.01% urea and 4.0% glucose in a 5L fermenter. The results showed that nineteen kinds of amino acid including GABA at C. protothecoides sample were analyzed using high performance liquid chromatography (HPLC). Glutamic acid in total concentration (%) of amino acid is the most abundant amino acid (33.10%), followed by alanine (20.48%) and GABA (17.48%). Three amino acids including GABA were responsible for more than 70% total concentration in C. protothecoides sample including eight essential and nine non-essential amino acids: aspartic acid, asparagine, serine, glutamine, histidine, glycine, threonine, arginine, tyrosine, valine, methionine, tryptophan, phenylalanine, isoleucine, leucine, lysine. As a result of this experiment, it is expected that Chlorella will be developed to a critical product having high value as, GABA, functional food materials.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.10
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• pp.1483-1489
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• 2016

Most of amino acid (AA) digestibility values for feed ingredients are obtained using pigs cannulated in the distal ileum. The ileal-cannulated pig model uses pigs older than six weeks due to difficulties related to implanting the T-cannula in distal ileum of younger pigs and complications during the post-surgical recovery. However, to properly formulate the diet of weaned pigs, the nutritive value of feed ingredients should be determined with younger pigs. Thus, 25 weaned pigs were used to determine the apparent total tract digestibility (ATTD) of nutrients, energy, and apparent ileal digestibility (AID) and standardized ileal digestibility (SID) ileal AA digestibility of broken rice (BR), with or without multicarbohydrase (MC) and phytase (Phy) supplementation. Piglets were weaned at 23 d of age and individually housed in digestibility cages until 45 d of age. The trial consisted of 7 d of adaptation to the experimental diets and 3 d of excreta (feces and urine) collection. Ileal digesta was collected at slaughter (about 6 weeks of age). A completely randomized experimental design was used to determine the effects of MC and Phy. Reference diets (RD, 5% casein) was replaced by 30% of BR with or without MC, Phy, or MC+Phy. The RD was used to quantify endogenous AA losses. BR with Phy supplied had increased the ATTD of dry matter (p<0.05) and SID of histidine (p = 0.05), arginine, leucine, lysine, valine, alanine, and proline (p<0.05). BR with MC had been increased digestible energy and protein and SID for histidine (p<0.05). There was no interaction between Phy and MC on the BR nutrient digestibilities. Standardized amino acid digestibilities of BR, without enzymes, were lower than those values reported in the literature. The MC and Phy improved the digestibility of some nutrients and energy of BR in post-weaned piglet diets.