Journal of Microbiology

Research Support, Non-U.S. Gov't

Stable Expression and Secretion of Polyhydroxybutyrate Depolymerase of Paucimonas lemoignei in Escherichia coli: Se Whan Park , Moon Gyu Chung , Hwa Young Lee , Jeong Yoon Kim , Young Ha Rhee; J. Microbiol. 2008;46(6):662-669. Published online December 24, 2008; DOI: https://doi.org/10.1007/s12275-008-0283-z

Abstract: An efficient strategy for the expression and secretion of extracellular polyhydroxybutyrate depolymerase (PhaZ1) of Paucimonas lemoignei in Escherichia coli was developed by employing the signal peptide of PhaZ1 and a truncated ice nucleation protein anchoring motif (INPNC). Directly synthesized mature form of PhaZ1 was present in the cytoplasm of host cells as inclusion bodies, while a construct containing PhaZ1 and its own N-terminal signal peptide (PrePhaZ1) enabled the secretion of active PhaZ1 into the extracellular medium. However, the PrePhaZ1 construct was harmful to the host cell and resulted in atypical growth and instability of the plasmid during the cultivation. In contrast, INPNC-PhaZ1 and INPNCPrePhaZ1 fusion constructs did not affect growth of host cells. INPNC-PhaZ1 was successfully displayed on the cell surface with its fusion form, but did not retain PhaZ1 activity. In the case of INPNC-PrePhaZ1, the initially synthesized fusion form was separated by precise cleavage of the signal peptide, and active PhaZ1 was consequently released into the culture medium. The amount of PhaZ1 derived from E. coli (INPNC-PrePhaZ1) was almost twice as great as that directly expressed from E. coli (PrePhaZ1), and was predominantly (approximately 85%) located in the periplasm when cultivated at 22°C but was efficiently secreted into the extracellular medium when cultivated at 37°C.

Biosynthesis of polyhydroxybutyrate and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by bacillus thuringiensis R-510: Park, Sang Kyu , Lee, Kang Tae , Kim, Young Baek , Rhee, Young Ha; J. Microbiol. 1997;35(2):127-133.

Abstract: Biosynthesis of polyhydroxybutyrate and copolymer consisting of 3-hydroxybutyrate and 3-hydroxyvalerate [poly(3HB-co-3HV)] by Bacillus thuringiensis R-510 grown with glucose or with mixtures of glucose and propionate was investigated. n-Alkanoic acids other than propionate were not precursors of 3HV units. The fraction of 3HV unit in the copolymer increased from 0 to 84 mol% of 3HV. Polymer yield decreased as the fraction of propionate was increased but the molecular weight distribution was not affected by the composition of carbon substrate. The minimum melting temperature (around 65℃) of poly (3HB-co-3HV) copolymers was observed for the polymer bearing approximately 35 mol% of 3HV. Polyhydroxyalkanoates production by this organism was not dependent on nutritional limitation, but remarkably influenced by dissolved oxygen concentration in the culture medium. Low level of dissolved oxygen concentration prevented spore formation in the cells and stimulated the synthesis of polyhydroxyalkanoate. The composition of poly (3HB-co-3HV) produced by B. thuringiensis R-510 lyhydroxyalkanoate. The composition of poly(3HB-co-3HV) produced by B. thuringiensis R-510 varied according to the growth time. However, there was no evidence that polymers isolated from cells were mixtures of immiscible polymers.

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