• 한국식품과학회지
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• 제19권1호
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• pp.42-49
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• 1987

L.helveticus YM-1 과 Str.lactis ${ML}_3$를 탈지유, 배양여액및 함성배지에 단독및 혼합배양 하였을때 산생성량과 당이용성 그리고 상관관계를 검토하였다. 자기자신의 배양여액보다 상대편의 배양여액에서, 단독배양보다 혼합배양의 경우가 산생성 촉진효과가 컸었다. 유당의 이용성은 12시간 배양했을때 Str. lactis ${ML}_3$ 의 경우 0.4%, L.helveticus YM-1은 0.85%. 혼합배양시는 1.05%였다. L.helveticus YM -1의 단독배양과 두균의 혼합배양의 경우 8시간후 배지에 생성된 포도당은 0.22%와 0.10%를 나타낸 다음 점차 감소하였다. L.helveticus YM-1에 의해서 생성된 포도당은 Str.lactis ${ML}_3$의 산생성을 촉진한다고 생각된다.

• 한국미생물·생명공학회지
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• 제47권3호
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• pp.449-458
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• 2019

Hepatitis B treatments using immune therapy are gaining interest because of the improvements in dendritic cell performance for antigen presentation, which induces an appropriate immune response and raises patient survival rates. This research aims to produce a significant amount of the HBcAg antigen, which can induce an immune response and have a curative effect on HBV infection. In this study, the HBV subgenotype B3 of the HBcAg gene was used, which is dominant in Indonesia. Further, Lactococcus lactis bacteria was used as the host because of its safety and tightly regulated protein expression. The codon usage for the HBcAg gene was optimized to improve protein expression in L. lactis, which is important because a codon is not random between species. The HBcAg gene is attached to a pNZ8148 plasmid and transformed into the L. lactis NZ3900 expression host. The results confirm that a positive protein band (21 kDa) in two fractions of purified HBcAg was recognized by both western blotting and dot blot hybridization, even if the HBcAg optimized codon has higher GC contents than that suggested for L. lactis expression. Overall, this research strengthens the broad use of L. lactis bacteria for any protein expression, including higher protein expression of codon optimized HBcAg gene compared to non-optimized genes. Furthermore, the improvement in the codon optimization of the HBcAg gene significantly increases the total protein expression by 10-20%, and the expression level of the codon optimized HBcAg increases 1.5 to 3.2-times that of the native HBcAg.

• Journal of Microbiology and Biotechnology
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• 제6권1호
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• pp.50-53
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• 1996

A cultured milk product was made by fennenting 10$\%$ reconstituted skim milk with Lactococcus lactis subsp. lactis TA29 and Saccharomyces exiguus SK2. L. lactis TA29 and S. exiguus SK2 grew up to 1.0 $\times 10^9\;and\;2.0 \times 10^6$ cfu/ml, respectively. After the fermentation 21$\%$ of lactose was hydrolyzed, pH was lowered to 4.2, and titratable acidity and alcohol concentration were increased to 0.96 and 0.023$\%$, respectively. When the fermented milk was stored at $4{\circ}C$ for 9 days, the viable cell counts for L. lactis TA29 and S. exiguus SK2 were $6.5 \times 10^5\;and\;1.6 \times 10^6$ cfu/rnl, respectively. The alcoholic fermented milk prepared in this experiment was more inhibitory against some pathogenic bacteria including C. perfringens than commercial yoghurt products tested.

• 한국축산식품학회지
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• 제42권1호
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• pp.46-60
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• 2022

In this study, angiotensin-I-converting enzyme inhibitory (ACEI) activity was evaluated in fermented goat milk fermented by lactic acid bacteria (LAB) from fermented foods and breast milk. Furthermore, the potential for ACEI peptides was identified in fermented goat milk with the highest ACEI activity. The proteolytic specificity of LAB was also evaluated. The 2% isolate was inoculated into reconstituted goat milk (11%, w/v), then incubated at 37℃ until pH 4.6 was reached. The supernatant produced by centrifugation was analyzed for ACEI activity and total peptide. Viable cell counts of LAB and titratable acidity were also evaluated after fermentation. Peptide identification was carried out using nano liquid chromatography mass spectrometry (LC-MS/MS), and potential as an ACEI peptide was carried out based on a literature review. The result revealed that ACEI activity was produced in all samples (20.44%-60.33%). Fermented goat milk of Lc. lactis ssp. lactis BD17 produced the highest ACEI activity (60.33%; IC₅₀ 0.297±0.10 mg/mL) after 48 h incubation, viable cell counts >8 Log CFU/mL, and peptide content of 4.037±0.27/mL. A total of 261 peptides were released, predominantly derived from casein (93%). The proteolytic specificity of Lc. lactis ssp. lactis BD17 through cleavage on the amino acid tyrosine, leucine, glutamic acid, and proline. A total of 21 peptides were identified as ACEI peptides. This study showed that one of the isolates from fermented food, namely Lc. lactis ssp. lactis BD17, has the potential as a starter culture for the production of fermented goat milk which has functional properties as a source of antihypertensive peptides.

• Journal of Microbiology and Biotechnology
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• 제31권1호
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• pp.154-162
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• 2021

L-5-methyltetrahydrofolate (5-MTHF) is one of the biological active forms of folate, which is widely used as a nutraceutical. However, low yield and serious pollution associated with the chemical synthesis of 5-MTHF hampers its sustainable supply. In this study, 5-MTHF production was improved by engineering the 5-MTHF biosynthesis pathway and NADPH supply in Lactococcus lactis for developing a green and sustainable biosynthesis approach. Specifically, overexpressing the key rate-limiting enzyme methylenetetrahydrofolate reductase led to intracellular 5-MTHF accumulation, reaching 18 ㎍/l. Next, 5-MTHF synthesis was further enhanced by combinatorial overexpression of 5-MTHF synthesis pathway enzymes with methylenetetrahydrofolate reductase, resulting in 1.7-fold enhancement. The folate supply pathway was strengthened by expressing folE encoding GTP cyclohydrolase I, which increased 5-MTHF production 2.4-fold to 72 ㎍/l. Furthermore, glucose-6-phosphate dehydrogenase was overexpressed to improve the redox cofactor NADPH supply for 5-MTHF biosynthesis, which led to a 60% increase in intracellular NADPH and a 35% increase in 5-MTHF production (97 ㎍/l). To reduce formation of the by-product 5-formyltetrahydrofolate, overexpression of 5-formyltetrahydrofolate cyclo-ligase converted 5-formyltetrahydrofolate to 5,10-methyltetrahydrofolate, which enhanced the 5-MTHF titer to 132 ㎍/l. Finally, combinatorial addition of folate precursors to the fermentation medium boosted 5-MTHF production, reaching 300 ㎍/l. To the best of our knowledge, this titer is the highest achieved by L. lactis. This study lays the foundation for further engineering of L. lactis for efficient 5-MTHF biosynthesis.

• Journal of Applied Biological Chemistry
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• 제53권3호
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• pp.126-131
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• 2010

대두가공공정 중 발생하는 부산물인 대두배아 및 대두 단백질을 이용하여 Bifidobacterium lactis BL740의 생균수 및 대두 이소플라본 비배당체 생산 최대화를 위한 배지최적화를 수행하였고 이를 위하여 통계적 방법인 fractional factorial design (FFD) 및 central composite design(CCD)를 이용, 대두 유래 성분들이 포함된 배지 (S-medium)의 최적 조성물을 확언하였다. FFD의 경우 glucose, cellobiose, fructooligosaccharidde, soy peptone, soy protein, 대두배아를 이용 총 6가지 요소를 2수준에서 적용하였으며 이 중 soy protein, soy peptone 그리고 대두 배아가 B. lactis BL740의 균성장 혹은 대두 이소플라본 비배당체 전환에 중요 인자로 확인이 되었다. FFD에서 확인된 3가지 인자를 CCD에 적용하였으며 이를 통해 균성장의 경우 최적의 배지조성함량이 soy peptone 29.55 g/L, soy protein 12.73 g/L, 대두 배아 130.67 g/L로 확인되었으며 비배당체 전환의 경우 soy peptone 1.25 g/L, soy protein 2.06 g/L, 대두 배아 60.02 g/L로 최적화 되었다.

• Journal of Ginseng Research
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• 제42권4호
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• pp.412-418
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• 2018

Background: Ginsenoside Rg3(S) and compound K (C-K) are pharmacologically active components of ginseng that promote human health and improve quality of life. The aim of this study was to produce Rg3(S) and C-K from ginseng extract using recombinant Lactococcus lactis. Methods: L. lactis subsp. cremoris NZ9000 (L. lactis NZ9000), which harbors ${\beta}$-glucosidase genes (BglPm and BglBX10) from Paenibacillus mucilaginosus and Flavobacterium johnsoniae, respectively, was reacted with ginseng extract (protopanaxadiol-type ginsenoside mixture). Results: Crude enzyme activity of BglBX10 values comprised 0.001 unit/mL and 0.003 unit/mL in uninduced and induced preparations, respectively. When whole cells of L. lactis harboring pNZBglBX10 were treated with ginseng extract, after permeabilization of cells by xylene, Rb1 and Rd were converted into Rg3(S) with a conversion yield of 61%. C-K was also produced by sequential reactions of the permeabilized cells harboring each pNZBgl and pNZBglBX10, resulting in a 70% maximum conversion yield. Conclusion: This study demonstrates that the lactic acid bacteria having specific ${\beta}$-glucosidase activity can be used to enhance the health benefits of Panax ginseng in either fermented foods or bioconversion processes.

• 한국식품과학회지
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• 제43권2호
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• pp.169-175
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• 2011

[ ${\beta}$ ]Xylosidase 효소활성이 높은 균주를 선발하기 위하여 다양한 김치에서 분리된 Leuconostoc 속 젖산균의 ${\beta}$-xylosidase 활성을 탐색하였다. 김치에서 분리된 55개의 Leuconostoc 속 젖산균 중 36개의 균주만이 자일로스를 탄소원으로 이용하였으며, 배추김치에서 분리된 Leu. lactis KCTC 13344 균주가 가장 높은 세포내 ${\beta}$-xylosidase 효소활성을 나타내었으며, 효소활성은 pH 6, $30^{\circ}C$ 반응조건에서 가장 높게 나타났다. $Zn^{2+}$을 제외한 금속이온은 효소활성을 유의적으로 증가시켰으며, $Fe^{2+}$은 1 mM의 농도에서 ${\beta}$-xylosidase 대조구와 비교하여 효소활성을 약 40% 증가시켰다. 균주를 배양할 때 사용한 탄소원 중 자일로스가 가장 높은 효소활성을 나타내었고, 효소활성을 위한 최적의 자일로스 농도는 30 g/L였다. 단백질 전기영동 및 활성염색을 수행한 결과 분자량이 약 64 kDa인 Leu. lactis KCTC 13344 균주의 ${\beta}$-xylosidase는 자일로스에 의하여 발현이 유도되는 것으로 추정되었다. 자일로스가 30 g/L의 농도로 첨가된 MRS 배지에서 Leu. lactis KCTC 13344 균주의 성장은 20시간 후에 최고에 도달하였고, ${\beta}$-xylosidase 효소활성은 16시간 후에 최대 $7.1{\pm}0.3units/mL$이었다. 배양 초기에 주입한 자일로스는 약 20% 정도 소모하였고, 젖산과 아세트산은 3.0 g/L 수준으로 생성되었지만 에탄올은 생성되지 않았다.

• 산업식품공학
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• 제21권4호
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• pp.383-390
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• 2017

국내 재래시장에서 수집한 발효식품 등에서 우수한 glucansucrase 활성을 나타내는 유산균주를 분리한 후 이 균주를 이용한 올리고당 생성의 최적 조건을 조사하였다. 배추김치로부터 분리된 유산균주 CCK940은 glucansucrase 활성이 918.2 mU/mL로 가장 높아 본 올리고당 생산을 위한 균주로 선정하였고, Leu. lactis CCK940로 동정 및 명명되었다. 선정된 Leu. lactis CCK940는 배지의 pH를 6.0으로 조정하고 공여체인 sucrose와 수용체인 maltose의 초기 농도를 각각 5% (w/v)와 10% (w/v)로 첨가한 후 배양 4시간과 8시간째에 sucrose를 5% (w/v) 첨가하는 것이 최적인 것으로 확인되었다. 최적 조건에 12시간 배양 시 Leu. lactis CCK940는 중합도가 2-4인 올리고당을 최소 4종류 생성하였다. 본 균주는 수용체 분자로서 fructose와 melibiose를 사용할 수 없었다.

• Journal of Microbiology and Biotechnology
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• 제4권4호
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• pp.327-332
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• 1994

Optimum conditions for the production of acetoin and ammonia as the precursors of tetramethylpyrazine(TMP) were determined using Lactococcus lactis subsp. lactis biovar. diacetylactis FC1 in a modified Lactose-citrate broth containing galactose, citrate, and arginine. The cell growth and the productivity of acetoin and ammonia were remarkably increased in an aerobic culture with 10 $\mu M$ of hematin. For the optimum conditions of acetoin and ammonia production, the concentration of citrate and arginine were adjusted to 156 mM and 50 mM after 18 hr cultivation, and citrate and galactose to 156 mM and 50 mM after 36 hr cultivation, respectively. In these conditions, acetoin and ammonia were produced to the final concentration of 127 mM and 195 mM, which were the highest concentations, respectively. The optimum conditions of the TMP production were also determined as follows; 4 hours at 121, pH 8.3, and the maximal yield of TMP under these conditions was 0.81 g/l.