• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.3
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• pp.113-120
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• 2011

Precipitated calcium carbonate(PCC), particularly calcite crystal, is extensively used as a pigment, filler or extender in various industries such as paper, paint, textile, detergents, adhesives, rubber and plastics, food, cosmetics, and biomaterials. PCC is conventionally produced through the gas-liquid carbonation process, which consists on bubbling gaseous $CO_2$ through a concentrated calcium hydroxide slurry. This study is aimed to find some factors for controlling the morphology of engineered PCC in lab-scaled mixing batch. The experimental designs were based on temperature variables, $Ca(OH)_2$ concentration, $CO_2$ flow rate, and electrical conductivity. The model of engineered PCC morphology was finally controlled by adjustment of electrical conductivity(6.0~7.0 mS/cm) and $Ca(OH)_2$ concentration(10 g/L). Orthorhombic calcite crystals were mostly created at high concentration and electrical conductivity conditions because the increased ratio of $Ca^{2+}$ and $CO{_3}^{2-}$ ions affects the growth rate of orthorhombic faces. Excess calcium spices were contributed to the growth of faces in calcium carbonate crystal, and the non-stoichiometric reaction was occurred between $Ca^{2+}$ and $CO{_3}^{2-}$ ions during carbonation process.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2011.10a
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• pp.9-18
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• 2011

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2011.10a
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• pp.105-106
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• 2011

• Microbiology and Biotechnology Letters
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• v.49 no.3
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• pp.298-304
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• 2021

Photosynthetic conversion through cyanobacteria and microalgae is an increasingly serious concern in the global warming crisis. Many value-added substances are produced through strain improvement, and much research and development is being conducted to determine its potential as an actual industrial strain. Economic barriers throughout processing production can be overcome to produce value-added chemicals by microalgal strains. In this study, we engineered cyanobacteria strains for the photosynthetic production of squalene and confirmed the continuous cultivation of CO₂ and light conditions. The free-inducer system of gene expression was developed at the cyanobacterial strains. Then, the squalene production level and growth of the recombinant cyanobacteria were analyzed and discussed. For bio solar-cell factories, the ability to regulate genes based on the free-inducer gene expression system promotes metabolic engineering research and construction to produce value-added chemicals.

• Journal of Microbiology and Biotechnology
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• v.34 no.2
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• pp.407-414
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• 2024

Phosphorus is an essential but non-renewable nutrient resource critical for agriculture. Luxury phosphorus uptake allows microalgae to synthesize polyphosphate and accumulate phosphorus, but, depending on the strain of algae, polyphosphate may be degraded within 4 hours of accumulation. We studied the recovery of phosphorus from wastewater through luxury uptake by an engineered strain of Synechocystis sp. with inhibited polyphosphate degradation and the effect of this engineered Synechocystis biomass on lettuce growth. First, a strain (∆phoU) lacking the phoU gene, which encodes a negative regulator of environmental phosphate concentrations, was generated to inhibit polyphosphate degradation in cells. Polyphosphate concentrations in the phoU knock-out strain were maintained for 24 h and then decreased slowly. In contrast, polyphosphate concentrations in the wild-type strain increased up to 4 h and then decreased rapidly. In addition, polyphosphate concentration in the phoU knockout strain cultured in semi-permeable membrane bioreactors with artificial wastewater medium was 2.5 times higher than that in the wild type and decreased to only 16% after 48 h. The biomass of lettuce treated with the phoU knockout strain (0.157 mg P/m²) was 38% higher than that of the lettuce treated with the control group. These results indicate that treating lettuce with this microalgal biomass can be beneficial to crop growth. These results suggest that the use of polyphosphate-accumulating microalgae as biofertilizers may alleviate the effects of a diminishing phosphorous supply. These findings can be used as a basis for additional genetic engineering to increase intracellular polyphosphate levels.