• Journal of Microbiology and Biotechnology
• /
• v.31 no.5
• /
• pp.717-725
• /
• 2021

This study aimed to optimize medium composition and culture conditions for enhancing the biomass of Lactobacillus plantarum 200655 using statistical methods. The one-factor-at-a-time (OFAT) method was used to screen the six carbon sources (glucose, sucrose, maltose, fructose, lactose, and galactose) and six nitrogen sources (peptone, tryptone, soytone, yeast extract, beef extract, and malt extract). Based on the OFAT results, six factors were selected for the Plackett-Burman design (PBD) to evaluate whether the variables had significant effects on the biomass. Maltose, yeast extract, and soytone were assessed as critical factors and therefore applied to response surface methodology (RSM). The optimal medium composition by RSM was composed of 31.29 g/l maltose, 30.27 g/l yeast extract, 39.43 g/l soytone, 5 g/l sodium acetate, 2 g/l K₂HPO₄, 1 g/l Tween 80, 0.1 g/l MgSO₄·7H₂O, and 0.05 g/l MnSO₄·H₂O, and the maximum biomass was predicted to be 3.951 g/l. Under the optimized medium, the biomass of L. plantarum 200655 was 3.845 g/l, which was similar to the predicted value and 1.58-fold higher than that of the unoptimized medium (2.429 g/l). Furthermore, the biomass increased to 4.505 g/l under optimized cultivation conditions. For lab-scale bioreactor validation, batch fermentation was conducted with a 5-L bioreactor containing 3.5 L of optimized medium. As a result, the highest yield of biomass (5.866 g/l) was obtained after 18 h of incubation at 30℃, pH 6.5, and 200 rpm. In conclusion, mass production by L. plantarum 200655 could be enhanced to obtain higher yields than that in MRS medium

• Journal of Microbiology and Biotechnology
• /
• v.32 no.11
• /
• pp.1471-1478
• /
• 2022

2'-Fucosyllactose (2'-FL), the most abundant fucosylated oligosaccharide in human milk, has multiple beneficial effects on human health. However, its biosynthesis by metabolically engineered Escherichia coli is often hampered owing to the insolubility and instability of α-1,2-fucosyltransferase (the rate-limiting enzyme). In this study, we aimed to enhance 2'-FL production by increasing the expression of soluble α-1,2-fucosyltransferase from Helicobacter pylori (FucT2). Because structural information regarding FucT2 has not been unveiled, we decided to improve the expression of soluble FucT2 in E. coli via directed evolution using a protein solubility biosensor that links protein solubility to antimicrobial resistance. For such a system to be viable, the activity of kanamycin resistance protein (Kan^R) should be dependent on FucT2 solubility. Kan^R was fused to the C-terminus of mutant libraries of FucT2, which were generated using a combination of error-prone PCR and DNA shuffling. Notably, one round of the directed evolution process, which consisted of mutant library generation and selection based on kanamycin resistance, resulted in a significant increase in the expression level of soluble FucT2. As a result, a batch fermentation with the ΔL M15 pBCGW strain, expressing the FucT2 mutant (F#1-5) isolated from the first round of the directed evolution process, resulted in the production of 0.31 g/l 2'-FL with a yield of 0.22 g 2'-FL/g lactose, showing 1.72- and 1.51-fold increase in the titer and yield, respectively, compared to those of the control strain. The simple and powerful method developed in this study could be applied to enhance the solubility of other unstable enzymes.

• Microbiology and Biotechnology Letters
• /
• v.51 no.2
• /
• pp.191-202
• /
• 2023

Elevated serum cholesterol is a main risk factor for heart disorders. Most probiotic products administered to lower cholesterol are dairy products which are not suitable for lactose-intolerant individuals. In this study, we assessed the cholesterol-lowering efficacy of LAB isolated from traditionally fermented drinks in diet-induced rats and determine their efficacy in the production of non-dairy, probiotic formulations using papaya juice. LAB were isolated from palm wine and corn beer on MRS agar using a pour-plate technique. Identification was carried out using 16S rRNA gene sequencing. A hypercholesterolemia model in which diet-induced Wistar albino rats were assigned into four groups was established. Oral gavage was carried out for 30 days. On the 31^st day, the rats were dissected and the serum lipid profile was analyzed using biochemical kits. A 10⁶ cfu/ml of a 24-h-old culture of selected lactobacilli was used to inoculate papaya juice and incubated at 37℃. Microbial and chemical changes were assessed during papaya fermentation and after four weeks of cold storage. Two selected isolates (Pw1 and Cb4) had in vitro cholesterol reduction of > 80%. These two isolates lowered lipid profile (triglyceride, total cholesterol, LDL-c) significantly, and increased HDL-c levels (p < 0.5) in the rat sera. Phylogenetic analysis showed that Pw1 was 98.86% similar to Limosilactobacillus fermentum, while Cb4 was 99.54% similar to Enteroccocus faecium. Both strains fermented papaya juice with cell viability reaching 8.92 × 10⁸ cfu/ml and 25.3 × 10⁸ cfu/ml respectively, and were still viable after 4 weeks of cold storage.

• Korean Journal of Food Science and Technology
• /
• v.15 no.2
• /
• pp.118-122
• /
• 1983

The whole eggs with of without added 1% of glucose, lactose and sucrose respectively were pasteurized at $58^{\circ}C$ for 30min and then incubated for 24 hrs after inoculating with S. lactis, L. casei and S. faecalis to investigate the changes in lactic acid bacterial cell counts, titable acidity and pH. Fresh eggs were not contaminated with common bacteria and Salmonella, Proliferation of L. casei was the best among those microorganisms in pasteurized whole egg without sugar added, and titrable acidity was the highst and pH the lowest in the eggs fermented with L. casei. However, lactic acid bacterial cell counts, titrable acidity and pH were changed significantly by the addition of sugar, especially the growth of S. faecalis was better than two other organisms, and lactic acid bacterial cell counts, titrable acidity and pH of the eggs fermented with S. faecalis were $2.5{\times}10^{10}$, 0.70 and 4.8 respectively after 24 hrs fermentation.

• Korean Journal of Food Science and Technology
• /
• v.31 no.1
• /
• pp.189-195
• /
• 1999

Isoflavones of soy milk were mainly present as sugar conjugates such as genistin and daidzin which a glucosyl residue was attached to their aglycones, genistein and daidzein through ${\beta}-glycosidic$ bond, respectively. When soy milk containing sucrose as a sugar source was fermented with lactic acid bacteria, small amount of lactic acid $(0.16{\sim}0.29%)$ was produced but isoflavone conjugates were fully hydrolyzed. Supplementation of glucose or lactose was required for normal lactic acid production and affected the hydrolysis of isoflavone conjugates in some lactic acid bacteria. In the case of Lactobacillus delbrueckii subsp. delbrueckii KCTC 1047, glycosidic bond of isoflavone was fully hydrolyzed regardless of glucose supplementation. But only $25{\sim}40%$ of daidzin and $65{\sim}80%$ of genistin was hydrolyzed when glucose was added into soy milk in the other lactic acid bacteria, Lactobacillus bulgaricus KCTC 3188, Lactobacillus casei KCTC 3109, Lactobacillus delbrueckii subsp lactis KCTC 1058, Lactobacillus lactis KCTC 2181. The hydrolyzing enzyme, ${\beta}-glucosidase$ produced by lactic acid bacteria except Lactobacillus delbrueckii subsp. delbrueckii KCTC 1047 could be considered as inducible in the fermentation of soy milk and its production was decreased when glucose was added.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.31 no.4
• /
• pp.583-588
• /
• 2002

Two microorganisms isolated from soybean curd residue (biji) were identified as Enterococcus faecium (51% homology) and Lactobacillus rhamnosus (99.5% homology) by using gram positive identification (GPI) card and API 50 CHL kit, respectively. Ent. faecium grew well in micronized full-fat soyflour (MFS) milk, indicating pH 4.9, 0.38% acidity and 1.8$\times$10$^{9}$ CFU/$m\ell$ of viable cell counts after fermentation for 20 hr. L. rhamnosus LL showed pH 6.5 and 4.6$\times$10$^{8}$ CFU/$m\ell$ viable cell counts, but enhanced acid production in MFS milk mixture fortified with skim milk or by the addition of 1% of glucose and lactose. On the other hand, Ent. faecium LL did not show increased acid production in MFS/skim milk and MFS milk fortified with sugar. The MFS/skim milk fermented by L. rhmnosus LS and Ent. faecium LL showed 600 mg% and 350 mg% lactic acid, respectively.

• Korean Journal of Agricultural Science
• /
• v.8 no.2
• /
• pp.171-178
• /
• 1981

In order to develope the suitable processing method of new alcohol fermented milk beverage, the lactic acid bacteria and the yeast were inoculated to various level of saccharide added milk. And the change of component and alcohol concentration in beverage were analysed and tested. The results obtained were summarized as follows: 1. By skim milk media was fermented by the 5 strains of lactic acid bacteria for 24 hours, most suitable acidity was appeared in the Str. lactis fermented beverage as 0.83% and the amino nitrogen contents was not much changed as 0.2mg/ml. 2. By the skim milk was added with 5% glucose, lactose and sucrose respectively and fermented by the Str. lactis and Cruyveromyces fragilis, the acidity and amino nitrogen contents in beverage were not changed significantly, but alcohol concentration was increased from 2.5% to 3.58%. 3. By the 5% to 15% sucrose added skim milk media was fermented by Cruyveromyces fragilis and Saccharomyces cerevisiae, the amino nitrogen concentration was not so much changed by increasing sucrose contents. And the alcohol concentration was increased from 2.12% to 8.15% by Cruyveromyces fragilis fermentation and from 0% to 7.45% by S.accharomyces cerevisiae fermentation. 4. Sensory evaluation was better in the Cruyveromyces fragilis fermented beverage than Saccharomyces cerevisiae fermented beverage. 5. The contents of moisture, crude protein, ash and the concentrate of alcohol of Str. lactis and Cruyveromyces fragilis fermented skim milk beverage were much similar to koumis.

• Korean Journal of Agricultural Science
• /
• v.23 no.1
• /
• pp.70-79
• /
• 1996

Yogurts were prepared with skim milk powder added with jujube extract of 0%, 1%, 2%, 3%, 4%, 5%, respectively and fermented by mixed culture(Str. thermophilus, and Lac. bulgaricus). The fermented yogurts were evaluated for acid production(pH, titratable acidity), number of viable cell, change of sugars, sensory properties. 1. Addition of jujube extract increased acid production and decreased pH. Acid production was increased in proportion to concentration of jujube extracts added to milk and pH was decreased. 2. In yogurt fermentation, the lactic acid bacteria of yogurt added with jujube extract, increased in proportion to jujube extract concentration added to milk. 3. The viscosity was increased in proportion to concentration of jujube extract during 6 hrs. of fermentation. The viscosity of yogurt added with 4% and 5% jujube extract remarkably decreased for the first 12 hrs. Yogurt added with 5% jujube extract is lowest in its viscosity among the treatments. 4. The concentrations of glucose and fructose were higher in proportion of jujube extract add at 0 hrs. the concentration of lactose was decreased simultaneously, and those of galactose was increased in all the samples at 12 hrs. 5. The taste and odor of yogurt added with the jujube extract of 4% and 5%, respectively, were better than other samples. The color of control was better than other samples. The texture of control yogurt was better than orther samples, but was not clearly difference with the yogurts added with jujube extract of 4% and 5%. In the overall acceptability, the sensory scores of yogurt added with jujube extract of 3% and 4% were higher than other samples.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.28 no.6
• /
• pp.812-813
• /
• 1995

Lactococcal cells are nutritionally fastidious and thus, generally cultured either in milk or M17 medium (Terzaghi and Sandine, 1975). In this study, Lactococcus cremoris wild-type (KH) and its less­proteolytic mutant (KHA1) cells were grown on the M17 medium or with modified M17 medium by replicated parallel experiments. The modified M17 medium had the same composition as M17 medium, except that lactose was replaced by glucose. Analyses of culture-broth samples, in which the M17 and the modified M17 media were used, were conducted by high-performance liquid chromatography (HPLC). But, working with these media created noisy problems in analyses of samples. Therefore, a new semi-synthetic medium was developed on the basis of nutritional requirements (Morishita et al., 1981). The composition of the semi-synthetic medium determined on the basis of the nutritional requirements and the composition of milk, is presented in Table 1. The composition of M17 medium is also presented and compared in the table. L. cremoris KH and KHA1 cells were grown again on the new synthetic medium containing glucose or lactose. The broth samples were then drawn and analyzed by HPLC. Clearer separations of fermented products were achieved from the new medium than those with the M17 and the modified M17 media. In comparison with the M17 or the modified M17 media, growth on the new medium was good (Kim et al, 1993). Additional fermentations were also carried out at a controlled pH of 7.0, where enhanced growth of lactococcal cells was obtained. In the fermentations, samples were also analyzed for the concentrations of sugar and lactic acid. The results showed that the new synthetic medium was as good as or better than the M 17 and the modified M 17 media. This is because casein hydrolysate in the synthetic medium provided a ready supply of amino acids and peptides for L. cremoris KH and KHA1 cells. Lactic acid bacteria (LAB) including Lactococcal cells have been known to be an effective means of preserving foods, at the same time as giving particular tastes in fields of dairy products. LAB also have always occupied an important place in the technology of sea products, and marine LAB have known to be present in traditional fermented products (Ohhira et al, 1988). To apply the new synthetic medium to marine LAB, two different LAB were isolated from pickled anchovy and pollacks caviar and were grown on the new media in which various concentrations of NaCl $(3, 5, 7 and 10\%)$ added. They were also grown on the medium solution in natural seawater $(35\%o\;salinity)$ and on the solution of natural seawater itself, too. As seen in Fig. 1, Marine LAB were grown best on the synthetic medium solution in natural seawater and the higher concentrations of NaCl were added to the medium, the longer lag-phase of growth profile appeared. Marine LAB in natural seawater were not grown well. From these results, the synthetic medium seems good to cultivate cells which are essential to get salted fish aged. In this study, it showed that the new synthetic medium provided adequate nutrition for L. cremoris KH and KHA1 cells, which have been used as cheese starters (Stadhouders et al, 1988). Using this new medium, the acid production capability of starter cultures could be also measured quantitatively. Thus, this new medium was inferior to the M17 or the modified M17 medium in culturing the cheese starters and in measuring fermentation characteristics of the starter cells. Moreover, this new medium found to be good for selected and well-identified marine LAB which are used in rapid fermentations of low-salted fish.