• Journal of Microbiology and Biotechnology
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• v.26 no.3
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• pp.441-451
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• 2016

Squalene is a linear triterpene formed via the MVA or MEP biosynthetic pathway and is widely distributed in bacteria, fungi, algae, plants, and animals. Metabolically, squalene is used not only as a precursor in the synthesis of complex secondary metabolites such as sterols, hormones, and vitamins, but also as a carbon source in aerobic and anaerobic fermentation in microorganisms. Owing to the increasing roles of squalene as an antioxidant, anticancer, and anti-inflammatory agent, the demand for this chemical is highly urgent. As a result, with the exception of traditional methods of the isolation of squalene from animals (shark liver oil) and plants, biotechnological methods using microorganisms as producers have afforded increased yield and productivity, but a reduction in progress. In this paper, we first review the biosynthetic routes of squalene and its typical derivatives, particularly the squalene synthase route. Second, typical biotechnological methods for the enhanced production of squalene using microbial cell factories are summarized and classified. Finally, the outline and discussion of the novel trend in the production of squalene with several updated events to 2015 are presented.

• KSBB Journal
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• v.11 no.5
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• pp.550-556
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• 1996

A complex medium was developed for the production of microbial cellulose by Acetobacter xylinum ATCC 23769. The optimum concentration of each nutrient for the production of microbial cellulose was determined to be 10g peptone, 20g yeast extract, 5g glucose, 1.56g Na2HPO4, 1.8g KH2PO4, 0.05g MgSO4, 0.002g FeCl3, 5g citric acid and 10 mL ethanol per liter. With synergistic effects of citric acid and ethanol, cellulose productivity achieved in developed medium was 0.446 gram of cellulose per gram glucose for static culture, which is much higher than reported values. Cell growth and the cellulose production in the developed medium under static culture was also investigated.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.2
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• pp.225-234
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• 2006

Characteristics of electricity production from major fermentation products (acetate, propionate and butyrate) were evaluated in a microbial fuel cell (MFC). For each substrate, batch and continuous experiments were performed. The batch test result indicated that coulombic efficiency depended on the resistance connected in MFC circuit. With acetate, coulombic efficiency were 87% at $20{\Omega}$, but decreaced to 45% at$220{\Omega}$. In continuous tests, maximum power densities obtained was 220 Q with acetate. The maximum power densities of butyrate, acetate and propionate were 6.8, 6.1, and $5.2mW/m^2$, respectively. Propionate and butyrate were converted into acetate producing high currents. $H_2$ produced during butyrate and propionate probably used to produce electricity. In conclusion, butyrate conversion into acetate was faster than that of propionate with higher electricity production. If the production of propionate is inhibited during fermentation, anaerobically fermented liguor may be effectively applied for MFC.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.11
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• pp.1590-1597
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• 2017

Objective: This study aims to identify the relationship between odd- and branched-chain fatty acids (OBCFAs) and microbial nucleic acid bases in the rumen, and to establish a model to accurately predict microbial protein flow by using OBCFA. Methods: To develop the regression equations, data on the rumen contents of individual cows were obtained from 2 feeding experiments. In the first experiment, 3 rumen-fistulated dry dairy cows arranged in a $3{\times}3$ Latin square were fed diets of differing forage to concentration ratios (F:C). The second experiment consisted of 9 lactating Holstein dairy cows of similar body weights at the same stage of pregnancy. For each lactation stage, 3 cows with similar milk production were selected. The rumen contents were sampled at 4 time points of every two hours after morning feeding 6 h, and then to analyse the concentrations of OBCFA and microbial nucleic acid bases in the rumen samples. Results: The ruminal bacteria nucleic acid bases were significantly influenced by feeding diets of differing forge to concentration ratios and lactation stages of dairy cows (p<0.05). The concentrations of OBCFAs, especially odd-chain fatty acids and C15:0 isomers, strongly correlated with the microbial nucleic acid bases in the rumen (p<0.05). The equations of ruminal microbial nucleic acid bases established by ruminal OBCFAs contents showed a good predictive capacity, as indicated by reasonably low standard errors and high R-squared values. Conclusion: This finding suggests that the rumen OBCFA composition could be used as an internal marker of rumen microbial matter.

• KSBB Journal
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• v.7 no.2
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• pp.102-106
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• 1992

Effects of nitrogen souses and C/N ratio were investigated on the production of extracellular microbial surfaclant, sophorolipid, from C. bombiocola. Organic nitrogen sources, such as urea, peptone and yeast extract was found to be more effective for sophorolipid production, than inorganic nitrogen sources. Depending on the nitrogen sources, sophorolipid production pattern varied by increasing C/N ratio. Increased production of sophrolipid could be obtained up to 90g/L by feeding carbon source again 2 days after cultivation.

• Journal of Life Science
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• v.11 no.1
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• pp.11-13
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• 2001

Several culture conditions affecting cellulose production by a newly isolated Acetobacter sp. A9 were examined by cultivating cells under shaking cultures. The inoculum size in the range of 1-10% (v/v) did not influence cellulose production. Maximum cellulose production was obtained with 200 rpm of agitation speed. The cells grown in the 75 ml of medium in a 250-ml conical flask produced the highest level of cellulose. The strain was able to produce cellulose at 25-3$0^{\circ}C$ with a maximum at 3$0^{\circ}C$. Cellulose production occurred at pH 4.5-7.5 with a maximum at pH6.5.

• The Korean Journal of Food And Nutrition
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• v.9 no.3
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• pp.336-340
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• 1996

Rhizopus japonicus had the highest chitosan productivity compared with the chitosan productivity among Rhizopus sp. strains. To increase the productivity of microbial chitosan from Rhizopus faponicus, production medium and incubation conditions were optimized. The composition of the medium and the incubation conditions were as follows : starch 2%, yeast extract 2.5%, KH2PO4 0.05%, MgSO4 0.01%, FeSO4 0.002%, MnSO4 0.002%, ZnSO4 0.002%, CaC12 0.002%, PH 5.5, incubation temperature medium compared with chitosan productivity.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.2
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• pp.139-146
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• 2009

In this study, characteristics of biological hydrogen production and microbial distribution were investigated with the wastewater of Tofu manufacturing process. Comparison of hydrogen production was conducted with acid or base pre-treatment of the wastewater. Maximum hydrogen production was acquired with combination of heat and acid treatment. Hydrogen production ($P_h$) and maximum hydrogen production rate ($R_h$) was calculated 661.01 mL and 12.21 mL/g dry wt biomass/hr from the modified Gompartz equation. Most of microbial community was analyzed as Streptococcus sp. from PCR-DGGE experiment of 16S rDNA. It was concluded that most significant microorganism for hydrogen production was Streptococcus gallolyticus sub sp. in this experiment.

• Journal of Microbiology and Biotechnology
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• v.33 no.2
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• pp.260-267
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• 2023

In this study, we sought to improve lutein and zeaxanthin production in Mychonastes sp. 247 and investigated the effect of environmental factors on lutein and zeaxanthin productivity in Mychonastes sp. The basic medium selection and N:P ratio were adjusted to maximize cell growth in one-stage culture, and lutein and zeaxanthin production conditions were optimized using a central composite design for two-stage culture. The maximum lutein production was observed at a light intensity of 60 μE/m²/s and salinity of 0.49%, and the maximum zeaxanthin production was observed at a light intensity of 532 μE/m²/s and salinity of 0.78%. Lutein and zeaxanthin production in the optimized medium increased by up to 2 and 2.6 folds, respectively, compared to that in the basic medium. Based on these results, we concluded that the optimal conditions for lutein and zeaxanthin production are different and that optimization of light intensity and culture salinity conditions may help increase carotenoid production. This study presents a useful and potential strategy for optimizing microalgal culture conditions to improve the productivity of lutein and zeaxanthin, which has applications in the functional food field.

• Journal of Life Science
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• v.30 no.10
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• pp.919-929
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• 2020

Aromatic compounds are widely used in the chemical, food, polymer, cosmetic, and pharmaceutical industries and are produced by mainly chemical synthesis using benzene, toluene, and xylene or by plant extraction methods. Due to many rising threats, including the depletion of fossil fuels, global warming, the strengthening of international environmental regulations, and the excessive harvesting of plant resources, the microbial production of aromatic compounds using renewable biomass is regarded as a promising alternative. By integrating metabolic engineering with synthetic and systems biology, artificial biosynthetic pathways have been reconstituted from L-tryptophan biosynthetic pathway in relevant microorganisms, such as Escherichia coli and Corynebacterium glutamicum, enabling the production of a variety of value-added aromatic compounds, such as 5-hydroxytryptophan, serotonin, melatonin, 7-chloro-L-tryptophan, 7-bromo-L-tryptophan, indigo, indirubin, indole-3-acetic acid, violacein, and dexoyviolacein. In this review, we summarize the characteristics, usage, and biosynthetic pathways of these aromatic compounds and highlight the latest metabolic engineering strategies for the microbial production of aromatic compounds and suitable solution strategies to overcome problems in increasing production titers. It is expected that strain development based on systems metabolic engineering and the optimization of media and bioprocesses using renewable biomass will enable the development of commercially viable technologies for the microbial production of many aromatic compounds.