Biosynthesis and Biodegradation of 3-Hydroxypropionate- Containing Polyesters

Abstract

3-Hydroxypropionate (3HP) is an important compound in the chemical industry, and the polymerized 3HPcan be used as a bioplastic. In this review, we focus on polyesters consisting of 3HP monomers, including the homopolyester poly(3-hydroxypropionate) and copolyesters poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxypropionate-co-3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate), poly(4-hydroxybutyrate-co-3-hydroxypropionate-co-lactate), and poly(3-hydroxybutyrate-co-3-hydroxypropionate-co-4-hydroxybutyrate-co-lactate). Homopolyesters like poly(3-hydroxybutyrate) are often highly crystalline and brittle, which limits some of their applications. The incorporation of 3HP monomers reduces the glass transition temperature, the crystallinity, and also, at up to 60 to 70 mol% 3HP, the melting point of the copolymer. This review provides a survey of the synthesis and physical properties of different polyesters containing 3HP.Bacterial polyhydroxyalkanoates (PHAs) are natural biodegradable thermoplastics produced by various microorganisms as intracellular energy and carbon storage compounds. PHAs have attracted increased attention as possible alternatives to petroleum-based polymers. They are biodegradable, insoluble in water, nontoxic, biocompatible, piezoelectric, thermoplastic, and/or elastomeric. These features make PHAs suitable for several applications in the packaging industry, medicine, pharmacy, agriculture, and food industry, as raw materials for the production of enantiomerically pure chemicals, and for the production of paints (2, 44). The best characterized PHA is poly(3-hydroxybutyrate) [poly(3HB)], which is synthesized by many bacteria (28,31,38,41). Unfortunately, poly(3HB) is a highly crystalline and brittle polymer with a low elongation-to-break factor, which has prevented its use in a wide range of applications. To obtain bacterial PHAs with improved physical and mechanical properties, previous studies have demonstrated the biosynthesis of copolyesters consisting of 3-hydroxybutyrate (3HB) and a second constituent. Pathways for the biosynthesis of such PHA copolyesters, like poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [poly(3HB-co-3HV)], poly(3-hydroxybutyrate-co-4-hydroxyvalerate) [poly(3HB-co-4HV)], and poly(3-hydroxybutyrate-co-3-hydroxypropionate)

Poly(3-Hydroxypropionate): a Promising Alternative to Fossil Fuel-Based Materials

“…With a melting point of about 77°C, a glass transition temperature of Ϫ20°C, and a fusion enthalpy value of 64 J/g (16,(18)(19)(20), it combines a low melting temperature, flexibility, and good degradability with the high stability of, e.g., poly(3HB) ( Table 1). Due to these favorable characteristics, several new metabolic pathways, processes, and hosts have been developed since the last review, which was published about 4 years ago (18). As there are still no microorganisms known to synthesize poly(3HP), all attempts rely on recombinant strains.…”

“…As we previously reported, the 3HP present in the polyester lowers glass transition temperature, crystallinity, fusion enthalpy, and melting temperature (18). Due to the limitations in the physical characteristics of poly(3HB), several copolymers have been developed to improve the performance of poly(3HB) (35)(36)(37).…”

Contemplating 3-Hydroxypropionic Acid Biosynthesis in Klebsiella pneumoniae

“…As a versatile precursor, 3-HP can be readily converted into a series of economically important chemicals, including 1,3-propandiol (1,3-PDO), 3-hydroxypropionaldehyde (3-HPA), acrylic acid, and malonic acid [2]. Additionally, the hydroxyl and carboxyl in 3-HP molecule can be polymerized to form poly-3-hydroxypropionate [3], which is a novel polymer displaying higher mechanical strength and elongation at break compared with poly lactic acid (2-hydroxypropionic acid). Because of its broad applications, 3-HP has been fueled in recent years.…”

Gene Arrangements in Expression Vector Affect 3-Hydroxypropionic Acid Production in Klebsiella pneumoniae

“…3-HP can be readily converted into a panel of economically important compounds, such as 1,3-propanediol (1,3-PDO), acrylic acid, and acrylamide [11,18]. In addition, 3-HP is a potential nematicide [16], or the monomer of poly-3-hydroxypropionic acid that has advantages over poly-bhydroxybutyrate (PHB) in several physical properties such as tensile strength and elongation at break [1,2]. To develop a low-cost 3-HP bioprocess, most research groups in the world use glycerol as carbon source because it is the main by-product of the flourishing biodiesel industries.…”