Improving β-carotene production in Escherichia coli by metabolic engineering of glycerol utilization pathway / 生物工程学报

Glycerol is a byproduct during biodiesel production. It is an important feedstock for fermentation due to its low price and high reduced status. Multiple genes of the glycerol utilization pathway were modulated in a previously engineered high β-carotene producing Escherichia coli strain CAR015 to enhance glycerol utilization capability for improving isoprenoids production. The glpR gene, encoding glycerol 3-phosphate repressor, was firstly deleted. The glpFK, glpD and tpiA genes were then modulated by three artificial regulatory parts, M1-37, M1-46 and M1-93, respectively. β-carotene titer reached 64.82 mg/L after modulating glpD with M1-46, which was 4.86 times higher than that of CAR015, and glycerol consumption rate also increased 100%. Modulating tpiA led to a little increase of β-carotene titer, whereas modulating glpFK led to a little decrease of β-carotene titer. This demonstrated that GlpD was a rate-limiting step in glycerol utilization pathway. Q-PCR of glpF, glpK, glpD and tpiA results showed that decrease the transcription level of glpF, glpK, glpD, or decrease the transcription level of tpiA could increase the cell growth and β-carotene production, probably for the decrease of methylglyoxal toxicity. Modulating glpD and tpiA genes in combination resulted in the best strain Gly003, which produced 72.45 mg/L β-carotene with a yield of 18.65 mg/g dry cell weight. The titer was 5.23 and yield 1.99 times of that of the parent strain CAR015. Our work suggested that appropriate activation of glpD and tpiA genes in glycerol utilization pathway could effectively improve β-carotene production. This strategy can be used for production of other terpenoids in E. coli.

Screening and identification of an ssDNA aptamer targeting the extracellular domain of Mucin16 by CE-SELEX / 医学研究生学报

Objective CA125 has been proved to be closely related to peritoneal metastasis of gastric cancer.This study aimed to screen and identify a novel ssDNA aptamer targeting the extracellular domain of Mucin16. Methods Using capillary elec-trophoresis, we screened the aptamers targeting the synthetic peptide of the extracellular domain of Mucin16 and quantitatively deter-mined the Kd value of each cycle and the affinity of the aptamers for the synthetic peptide by CE-SELEX.Then we evaluated the ability of the obtained aptamers to target cancer cells using confocal laser imaging. Results After five cycles of screening, sequencing, af-finity determination, we obtained an ssDNA aptamer targeting the extracellular domain of Mucin16, with a Kd value of 122.7 nm and visible green fluorescent signals on the cell membrane of the human ovarian cancer cell line expressing Mucin16, but not on that of the normal hepatocytes not expressing Mucin16.This confirmed the binding ability of the aptamer to the extracellular domain of Mucin16. Conclusion A novel aptamer targeting the synthetic peptide of the extracellular domain of Mucin16 was successfully obtained by capil-lary electrophoresis, which could be used as a new agent in the diagnosis and treatment of peritoneal metastasis of gastric cancer.

Improvement of Growth and Periplocin Yield of Periploca sepium Adventitious Root Cultures by Altering Nitrogen Source Supply / 中草药·英文版

Objective To increase the ultimate yield of periplocin in Periploca sepium adventitious root cultures by a two-stage culture based on nitrogen source.Methods Firstly,the effects of nitrogen source(NH-NO-)at different ratios and different total initial nitrogen amounts on the accumulation of biomass and secondary metabolites in adventitious root cultures of P sepium were investigated,and growth and production media for the two-stage culture based on the above results were established.Results The highest biomass and periplocin content were obtained in the culture medium of 15 mmol/L total nitrogen amount with NH-NO(1:2)and 30 mmol/L total nitrogen amount with nitrate as the sole nitrogen source.By adopting a fed-batch cultivation strategy,the dry weight adventitious root,periplocin content and yield were increased by 136%,108%,and 389%,respectively when compared with those of the control,reaching up to 8.13 g/L,157.15 μg/g,and 1277.63 μg/L,respectively.Furthermore,it was found that in the process of two-stage culture,the adventitious roots grew thicker significantly after they were transferred into production medium directly.Conclusion The ultimate yield of periplocin in P.sepium adventitious root cultures could be significantly increased by a two-stage culture based on nitrogen source.

Induction of Periploca sepium in vitro plantlet and studies on dynamic accumulation of periplocin / 中国中药杂志

<p><b>OBJECTIVE</b>To analyze the content of periplocin in different part of the Periploca sepium in vitro plantlet and study its dynamic variation during the process of differentiation.</p><p><b>METHOD</b>The seeds were generated seedling under aseptic condition, and the cut hypocotyl was induced to form the callus and adventitious buds on the MS culture medium with the hormone of IBA 0.1 mg x L(-1) + BA 1 mg x L(-1). The seedling was cut down when the buds grew up to 3 cm and then the root was cultured in the 1/2 MS culture medium with the hormone of IBA 0.5 mg x L(-1) to form intact plantlet. Different parts of it were collected and the content of periplocin was measured during the process of differentiation.</p><p><b>RESULT</b>The contents of periplocin varied widely in different parts during the process of differentiation, with the highest in the roots and then callus, stem and leaf of intact plantlet, stem and leaf of plantlet without root from high to low.</p><p><b>CONCLUSION</b>The periplocin of the secondary metabolite is more likely to be produced and accumulated in root and callus. Periplocin in stem and leaf is probably transported by conducting tissue.</p>