Sang Yup Lee - Academia.edu (original) (raw)

Papers by Sang Yup Lee

Process Biochemistry, 1999

Several factors affecting cell growth and succinic acid production by Anaerobiospirillum succinic... more Several factors affecting cell growth and succinic acid production by Anaerobiospirillum succiniciproducens were examined by cultivating cells under various conditions. Maximum specific growth rate in the flask cultivation increased with increasing initial glucose concentration up to 20 g/l glucose. The distribution of fermentation products was not affected by glucose concentration, and the ratio of fermentation products (g-acetic acid/g-succinic acid) was similar (1:4) for all glucose concentrations. Other carbon sources including lactose, sucrose, maltose, and fructose could be utilized by A. succiniciproducens. Cell concentration and the amount of succinic acid attainable was dependent on the inoculum size. Sodium ion was essential for cell growth and succinic acid production, and its optimum concentration was 4 g/l. Cell growth and succinic acid production were slightly enhanced at the optimum magnesium ion concentration of 0.4 g/l. Among the seven different complex nitrogen sources examined by Plackett-Burman design, only poylpeptone enhanced succinic acid production.

Enzyme and Microbial Technology, 2006

Succinic acid produced by various microorganisms can be used as a precursor of many industrially ... more Succinic acid produced by various microorganisms can be used as a precursor of many industrially important chemicals in food, chemical and pharmaceutical industries. The assessment of raw material cost and the estimation of the potential market size clearly indicate that the current petroleum-based succinic acid process will be replaced by the fermentative succinic acid production system in the foreseeable future. This paper reviews processes for fermentative succinic acid production, especially focusing on the use of several promising succinic acid producers including Actinobacillus succinogenes, Anaerobiospirillum succiniciproducens, Mannheimia succiniciproducens and recombinant Escherichia coli. Processes for the recovery of succinic acid from fermentation broth are also reviewed briefly. Finally, we suggest further works required to improve the strain performance suitable for successful commercialization of fermentative succinic acid production.

Biotechnology and Bioengineering, 1994

Alcaligenes eutrophus NCIMB 11599 was cultivated to produce poly(3-hydroxybutyric acid) (PHB) fro... more Alcaligenes eutrophus NCIMB 11599 was cultivated to produce poly(3-hydroxybutyric acid) (PHB) from glucose by the automatic fed-batch culture technique. The glucose concentration of the culture broth was controlled at 10 to 20 g/L by two methods: using exit gas data obtained from a mass spectrometer and using an on-line glucose analyzer. The effect of ammonium limitation on PHB synthesis at different culture phases was studied. The final cell concentration, PHB concentration, and PHB productivity increased as ammonia feeding was stopped at a higher cell concentration. High concentrations of PHB (121 g/L) and total cells (164 g/L) were obtained in 50 h when ammonia feeding was stopped at the cell concentration of 70 g/L. The maximum PHB content reached 76% of dry cell weight and the productivity was 2.42 g/L h with the yield of 0.3 g PHB/g glucose.

Canadian Journal of Microbiology, 1995

A number of Escherichia coli strains including K12, B, W, XL1-Blue, DH5 alpha, HB101, JM109, and ... more A number of Escherichia coli strains including K12, B, W, XL1-Blue, DH5 alpha, HB101, JM109, and C600 were transformed with the stable high-copy-number plasmid pSYL105 containing the Alcaligenes eutrophus polyhydroxyalkanoic acid biosynthesis genes, and were subsequently compared for their ability to synthesize and accumulate poly(3-hydroxybutyric acid) (PHB). The rate of PHB synthesis, the extent of PHB accumulation, and PHB yield from glucose varied considerably from one strain to another. Strains XL1-Blue and B harboring pSYL105 synthesized PHB at the highest rate to a final concentration of ca. 7 g/L in complex medium containing 20 g glucose/L. With an aim to reduce the cost of the medium, the effect on PHB accumulation of supplementing a defined medium with complex nitrogen sources was examined. A PHB concentration of 81 g/L could be obtained in 41 h from a pH-stat fed-batch culture of XL1-Blue(pSYL105) in a semidefined medium. When the availability of acetyl-CoA was increased by supplementing the medium with complex nitrogen sources, amino acids, or oleic acid, PHB synthesis by recombinant E. coli was enhanced.

Biotechnology Letters, 1993

Escherichia coli W was cultivated in the pH-stat fed-batch mode in a chemically defined medium co... more Escherichia coli W was cultivated in the pH-stat fed-batch mode in a chemically defined medium containing sucrose as a sole carbon source. A final cell concentration of 105 g/L could be obtained in 36 hrs by feeding 20 g sucrose+0.57 g MgSO47H2O for a definite on-time upon the pH rise. Using the same strategy, a recombinant strain harboring pSYL104 could also be grown to 125 g/L in 48 hrs.

Biotechnology and Bioengineering, 1996

Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates (HAs) synthesized by numerous ba... more Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates (HAs) synthesized by numerous bacteria as intracellular carbon and energy storage compounds and accumulated as granules in the cytoplasm of cells. More than 80 HAs have been detected as constituents of PHAs, which allows these thermoplastic materials to have various mechanical properties resembling hard crystalline polymer or elastic rubber depending on the incorporated monomer units. Even though PHAs have been recognized as good candidates for biodegradable plastics, their high price compared with conventional plastics has limited their use in a wide range of applications. A number of bacteria including Alcaligenes eutrophus, Alcaligenes latus, Azotobacter vinelandii, methylotrophs, pseudomonads, and recombinant Escherichia coli have been employed for the production of PHAs, and the productivity of greater than 2 g PHA/L/h has been achieved. Recent advances in understanding metabolism, molecular biology, and genetics of the PHA-synthesizing bacteria and cloning of more than 20 different PHA biosynthesis genes allowed construction of various recombinant strains that were able to synthesize polyesters having different monomer units and/or to accumulate much more polymers. Also, genetically engineered plants harboring the bacterial PHA biosynthesis genes are being developed for the economical production of PHAs. Improvements in fermentation/separation technology and the development of bacterial strains or plants that more efficiently synthesize PHAs will bring the costs down to make PHAs competitive with the conventional plastics.

Biotechnology and Bioengineering, 2001

Succinic acid was produced by fermentation of Anaerobiospirillum succiniciproducens using glycero... more Succinic acid was produced by fermentation of Anaerobiospirillum succiniciproducens using glycerol as a carbon source. When cells were anaerobically cultured in a medium containing 6.5 g/L glycerol, a high succinic acid yield (133%) was obtained while avoiding the formation of by-product acetic acid. The gram ratio of succinic acid to acetic acid was 25.8:1, which is 6.5 times higher than that obtained using glucose (ca. 4:1) as a carbon source. Therefore, succinic acid can be produced with much less by-product formation by using glycerol as a carbon source, which will facilitate its purification. When glucose and glycerol were cofermented with the increasing ratio of glucose to glycerol, the gram ratio of succinic acid to acetic acid and succinic acid yield decreased, suggesting that glucose enhanced acetic acid formation irrespective of the presence of glycerol. Glycerol consumption by A. succiniciproducens required unidentified nutritional components present in yeast extract. By intermittently feeding yeast extract along with glycerol, a high succinic acid yield (160%) could be obtained while still avoiding acetic acid formation. This resulted in the highest ratio of succinic acid to acetic acid (31.7:1).

Enzyme and Microbial Technology, 1999

Se¨eral en¨ironmental factors affecting the succinic acid production by Anaerobiospirillum succin... more Se¨eral en¨ironmental factors affecting the succinic acid production by Anaerobiospirillum succiniciproducens were studied. External CO supply had a negati¨e effect on cell growth at both pH 6.2 and pH 6.5, 2 while it had a somewhat positi¨e effect on succinic acid production. The effect of CO on succinic acid yield 2 was higher at pH 6.5 than pH 6.2. External supply of H enhanced the cell growth rate and succinic acid yield.

Biotechnology and Bioengineering, 1996

Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates (HAs) synthesized by numerous ba... more Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates (HAs) synthesized by numerous bacteria as intracellular carbon and energy storage compounds and accumulated as granules in the cytoplasm of cells. More than 80 HAs have been detected as constituents of PHAs, which allows these thermoplastic materials to have various mechanical properties resembling hard crystalline polymer or elastic rubber depending on the incorporated monomer units. Even though PHAs have been recognized as good candidates for biodegradable plastics, their high price compared with conventional plastics has limited their use in a wide range of applications. A number of bacteria including Alcaligenes eutrophus, Alcaligenes latus, Azotobacter vinelandii, methylotrophs, pseudomonads, and recombinant Escherichia coli have been employed for the production of PHAs, and the productivity of greater than 2 g PHA/L/h has been achieved. Recent advances in understanding metabolism, molecular biology, and genetics of the PHA-synthesizing bacteria and cloning of more than 20 different PHA biosynthesis genes allowed construction of various recombinant strains that were able to synthesize polyesters having different monomer units and/or to accumulate much more polymers. Also, genetically engineered plants harboring the bacterial PHA biosynthesis genes are being developed for the economical production of PHAs. Improvements in fermentation/separation technology and the development of bacterial strains or plants that more efficiently synthesize PHAs will bring the costs down to make PHAs competitive with the conventional plastics.

Poly(hydroxyalkanoic acid) [PHA] is accumulated by numerous microorganisms as an energy reserve m... more Poly(hydroxyalkanoic acid) [PHA] is accumulated by numerous microorganisms as an energy reserve material under unbalanced growth conditions in the presence of excess carbon source. In spite of being a good candidate for biodegradable thermoplastic, their high price compared with conventional plastics currently in use has limited their availability in a wide range of applications. With the aim of reducing the high production cost of PHA, much effort is currently being devoted to improve productivity by employing various microorganisms and by developing efficient culture techniques. Several processes recently developed and employed for the production of PHA by various bacteria are described.

Process Biochemistry, 1999

Several factors affecting cell growth and succinic acid production by Anaerobiospirillum succinic... more Several factors affecting cell growth and succinic acid production by Anaerobiospirillum succiniciproducens were examined by cultivating cells under various conditions. Maximum specific growth rate in the flask cultivation increased with increasing initial glucose concentration up to 20 g/l glucose. The distribution of fermentation products was not affected by glucose concentration, and the ratio of fermentation products (g-acetic acid/g-succinic acid) was similar (1:4) for all glucose concentrations. Other carbon sources including lactose, sucrose, maltose, and fructose could be utilized by A. succiniciproducens. Cell concentration and the amount of succinic acid attainable was dependent on the inoculum size. Sodium ion was essential for cell growth and succinic acid production, and its optimum concentration was 4 g/l. Cell growth and succinic acid production were slightly enhanced at the optimum magnesium ion concentration of 0.4 g/l. Among the seven different complex nitrogen sources examined by Plackett-Burman design, only poylpeptone enhanced succinic acid production.

Enzyme and Microbial Technology, 2006

Succinic acid produced by various microorganisms can be used as a precursor of many industrially ... more Succinic acid produced by various microorganisms can be used as a precursor of many industrially important chemicals in food, chemical and pharmaceutical industries. The assessment of raw material cost and the estimation of the potential market size clearly indicate that the current petroleum-based succinic acid process will be replaced by the fermentative succinic acid production system in the foreseeable future. This paper reviews processes for fermentative succinic acid production, especially focusing on the use of several promising succinic acid producers including Actinobacillus succinogenes, Anaerobiospirillum succiniciproducens, Mannheimia succiniciproducens and recombinant Escherichia coli. Processes for the recovery of succinic acid from fermentation broth are also reviewed briefly. Finally, we suggest further works required to improve the strain performance suitable for successful commercialization of fermentative succinic acid production.

Biotechnology and Bioengineering, 1994

Alcaligenes eutrophus NCIMB 11599 was cultivated to produce poly(3-hydroxybutyric acid) (PHB) fro... more Alcaligenes eutrophus NCIMB 11599 was cultivated to produce poly(3-hydroxybutyric acid) (PHB) from glucose by the automatic fed-batch culture technique. The glucose concentration of the culture broth was controlled at 10 to 20 g/L by two methods: using exit gas data obtained from a mass spectrometer and using an on-line glucose analyzer. The effect of ammonium limitation on PHB synthesis at different culture phases was studied. The final cell concentration, PHB concentration, and PHB productivity increased as ammonia feeding was stopped at a higher cell concentration. High concentrations of PHB (121 g/L) and total cells (164 g/L) were obtained in 50 h when ammonia feeding was stopped at the cell concentration of 70 g/L. The maximum PHB content reached 76% of dry cell weight and the productivity was 2.42 g/L h with the yield of 0.3 g PHB/g glucose.

Canadian Journal of Microbiology, 1995

A number of Escherichia coli strains including K12, B, W, XL1-Blue, DH5 alpha, HB101, JM109, and ... more A number of Escherichia coli strains including K12, B, W, XL1-Blue, DH5 alpha, HB101, JM109, and C600 were transformed with the stable high-copy-number plasmid pSYL105 containing the Alcaligenes eutrophus polyhydroxyalkanoic acid biosynthesis genes, and were subsequently compared for their ability to synthesize and accumulate poly(3-hydroxybutyric acid) (PHB). The rate of PHB synthesis, the extent of PHB accumulation, and PHB yield from glucose varied considerably from one strain to another. Strains XL1-Blue and B harboring pSYL105 synthesized PHB at the highest rate to a final concentration of ca. 7 g/L in complex medium containing 20 g glucose/L. With an aim to reduce the cost of the medium, the effect on PHB accumulation of supplementing a defined medium with complex nitrogen sources was examined. A PHB concentration of 81 g/L could be obtained in 41 h from a pH-stat fed-batch culture of XL1-Blue(pSYL105) in a semidefined medium. When the availability of acetyl-CoA was increased by supplementing the medium with complex nitrogen sources, amino acids, or oleic acid, PHB synthesis by recombinant E. coli was enhanced.

Biotechnology Letters, 1993

Escherichia coli W was cultivated in the pH-stat fed-batch mode in a chemically defined medium co... more Escherichia coli W was cultivated in the pH-stat fed-batch mode in a chemically defined medium containing sucrose as a sole carbon source. A final cell concentration of 105 g/L could be obtained in 36 hrs by feeding 20 g sucrose+0.57 g MgSO47H2O for a definite on-time upon the pH rise. Using the same strategy, a recombinant strain harboring pSYL104 could also be grown to 125 g/L in 48 hrs.

Biotechnology and Bioengineering, 1996

Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates (HAs) synthesized by numerous ba... more Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates (HAs) synthesized by numerous bacteria as intracellular carbon and energy storage compounds and accumulated as granules in the cytoplasm of cells. More than 80 HAs have been detected as constituents of PHAs, which allows these thermoplastic materials to have various mechanical properties resembling hard crystalline polymer or elastic rubber depending on the incorporated monomer units. Even though PHAs have been recognized as good candidates for biodegradable plastics, their high price compared with conventional plastics has limited their use in a wide range of applications. A number of bacteria including Alcaligenes eutrophus, Alcaligenes latus, Azotobacter vinelandii, methylotrophs, pseudomonads, and recombinant Escherichia coli have been employed for the production of PHAs, and the productivity of greater than 2 g PHA/L/h has been achieved. Recent advances in understanding metabolism, molecular biology, and genetics of the PHA-synthesizing bacteria and cloning of more than 20 different PHA biosynthesis genes allowed construction of various recombinant strains that were able to synthesize polyesters having different monomer units and/or to accumulate much more polymers. Also, genetically engineered plants harboring the bacterial PHA biosynthesis genes are being developed for the economical production of PHAs. Improvements in fermentation/separation technology and the development of bacterial strains or plants that more efficiently synthesize PHAs will bring the costs down to make PHAs competitive with the conventional plastics.

Biotechnology and Bioengineering, 2001

Succinic acid was produced by fermentation of Anaerobiospirillum succiniciproducens using glycero... more Succinic acid was produced by fermentation of Anaerobiospirillum succiniciproducens using glycerol as a carbon source. When cells were anaerobically cultured in a medium containing 6.5 g/L glycerol, a high succinic acid yield (133%) was obtained while avoiding the formation of by-product acetic acid. The gram ratio of succinic acid to acetic acid was 25.8:1, which is 6.5 times higher than that obtained using glucose (ca. 4:1) as a carbon source. Therefore, succinic acid can be produced with much less by-product formation by using glycerol as a carbon source, which will facilitate its purification. When glucose and glycerol were cofermented with the increasing ratio of glucose to glycerol, the gram ratio of succinic acid to acetic acid and succinic acid yield decreased, suggesting that glucose enhanced acetic acid formation irrespective of the presence of glycerol. Glycerol consumption by A. succiniciproducens required unidentified nutritional components present in yeast extract. By intermittently feeding yeast extract along with glycerol, a high succinic acid yield (160%) could be obtained while still avoiding acetic acid formation. This resulted in the highest ratio of succinic acid to acetic acid (31.7:1).

Enzyme and Microbial Technology, 1999

Se¨eral en¨ironmental factors affecting the succinic acid production by Anaerobiospirillum succin... more Se¨eral en¨ironmental factors affecting the succinic acid production by Anaerobiospirillum succiniciproducens were studied. External CO supply had a negati¨e effect on cell growth at both pH 6.2 and pH 6.5, 2 while it had a somewhat positi¨e effect on succinic acid production. The effect of CO on succinic acid yield 2 was higher at pH 6.5 than pH 6.2. External supply of H enhanced the cell growth rate and succinic acid yield.

Biotechnology and Bioengineering, 1996

Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates (HAs) synthesized by numerous ba... more Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates (HAs) synthesized by numerous bacteria as intracellular carbon and energy storage compounds and accumulated as granules in the cytoplasm of cells. More than 80 HAs have been detected as constituents of PHAs, which allows these thermoplastic materials to have various mechanical properties resembling hard crystalline polymer or elastic rubber depending on the incorporated monomer units. Even though PHAs have been recognized as good candidates for biodegradable plastics, their high price compared with conventional plastics has limited their use in a wide range of applications. A number of bacteria including Alcaligenes eutrophus, Alcaligenes latus, Azotobacter vinelandii, methylotrophs, pseudomonads, and recombinant Escherichia coli have been employed for the production of PHAs, and the productivity of greater than 2 g PHA/L/h has been achieved. Recent advances in understanding metabolism, molecular biology, and genetics of the PHA-synthesizing bacteria and cloning of more than 20 different PHA biosynthesis genes allowed construction of various recombinant strains that were able to synthesize polyesters having different monomer units and/or to accumulate much more polymers. Also, genetically engineered plants harboring the bacterial PHA biosynthesis genes are being developed for the economical production of PHAs. Improvements in fermentation/separation technology and the development of bacterial strains or plants that more efficiently synthesize PHAs will bring the costs down to make PHAs competitive with the conventional plastics.

Poly(hydroxyalkanoic acid) [PHA] is accumulated by numerous microorganisms as an energy reserve m... more Poly(hydroxyalkanoic acid) [PHA] is accumulated by numerous microorganisms as an energy reserve material under unbalanced growth conditions in the presence of excess carbon source. In spite of being a good candidate for biodegradable thermoplastic, their high price compared with conventional plastics currently in use has limited their availability in a wide range of applications. With the aim of reducing the high production cost of PHA, much effort is currently being devoted to improve productivity by employing various microorganisms and by developing efficient culture techniques. Several processes recently developed and employed for the production of PHA by various bacteria are described.