Abstract
Poly(3-hydroxypropionate) (P3HP) is a thermoplastic with great compostability and biocompatibility, and can be produced through several biosynthetic pathways, in which the glycerol pathway achieved the highest P3HP production. However, exogenous supply of vitamin B12 was required to maintain the activity of glycerol dehydratase, resulting in high production cost. To avoid the addition of VB12, we have previously constructed a P3HP biosynthetic route with β-alanine as intermediate, and the present study aimed to improve the P3HP production of this pathway. L-aspartate decarboxylase PanD was found to be the rate-limiting enzyme in the β-alanine pathway firstly. To improve the pathway efficiency, PanD was screened from four different sources (Escherichia coli, Bacillus subtilis, Pseudomonas fluorescens, and Corynebacterium glutamicum). And PanD from C. glutamicum was found to have the highest activity, the P3HP production was improved in flask cultivation with this enzyme. To further improve the production, the host strain was screened and the culture condition was optimized. Under optimal conditions, production and content of P3HP reached to 10.2 g/L and 39.1% (wt/wt [cell dry weight]) in an aerobic fed-batch fermentation. To date, this is the highest P3HP production without VB12.
Highlights
Poly(3-hydroxypropionate) (P3HP) is a promising polymer with high rigidity, ductility, and exceptional tensile strength in drawn films, and can be synthesized chemically by ring opening polymerization of β-propiolactone [1]
The phenomenon that addition of β-alanine improved P3HP production suggested the insufficient intracellular β-alanine supply, which could be caused by two possible reasons: low activity of L-aspartate decarboxylase (PanD) or low intracellular L-aspartate concentration
To figure out the restricting factor of β-alanine pathway, E. coli BL21(DE3) strain carrying pHP302 and pWQ513 (Q2153) was grown in shake flask, and 5 g/L β-alanine or L-aspartate was added into the medium
Summary
Poly(3-hydroxypropionate) (P3HP) is a promising polymer with high rigidity, ductility, and exceptional tensile strength in drawn films, and can be synthesized chemically by ring opening polymerization of β-propiolactone [1]. The chemical synthesis is not suitable for industrial scale production of P3HP because β-propiolactone is a human carcinogen. As 3-hydroxypropionate (3HP) is not a common metabolite in most organisms, biosynthesis of 3HP-containing polymers was usually based on structurally-related precursors, such as PLOS ONE | DOI:10.1371/journal.pone.0173150. P3HP with screened PanD study design, data collection and analysis, decision to publish, or preparation of the manuscript As 3-hydroxypropionate (3HP) is not a common metabolite in most organisms, biosynthesis of 3HP-containing polymers was usually based on structurally-related precursors, such as PLOS ONE | DOI:10.1371/journal.pone.0173150 March 2, 2017
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