Chemical and Biochemical Engineering Approaches in Manufacturing Polyhydroxyalkanoate (PHA) Biopolyesters of Tailored Structure with Focus on the Diversity of Building Blocks

Abstract

Polyhydroxyalkanoates (PHA) constitute prokaryotic storage materials not only harnessing microbial cells with benefits for survival under challenging environmental conditions, but also attracting attention as biological materials with properties resembling those of currently used thermoplasts and elastomers of petrochemical origin. Strongly dependent on their monomeric composition and microstructure, PHA´s exact material properties are predestined in statu nascendi, hence, during their biosynthesis. The present review sheds light on established and emerging strategies to produce differently composed PHA homo-, co-, ter-, and quarterpolyesters from the groups of short-, medium-, and long-chain PHA. It is shown how microbial strain selection, sophisticated genetic strain engineering based on synthetic biology approaches, advanced feeding strategies, and smart process engineering can be implemented to generate PHA of tailored monomeric composition, microstructure, molar mass, and molar mass distribution. Tailoring these parameters offers the possibility to produce customer-oriented PHA for various purposes, such as packaging materials, carriers of pharmaceutically active compounds, implants, or other emerging fields of use.

Introducing the Newly Isolated Bacterium Aneurinibacillus sp. H1 as an Auspicious Thermophilic Producer of Various Polyhydroxyalkanoates (PHA) Copolymers–2. Material Study on the Produced Copolymers

“…H1 is capable of production of PHA copolymers with a great variety of accessible monomer compositions resulting from the proper adjustment of cultivation conditions. As no special cultivation protocol for block copolymer biosynthesis described in [8] was adopted in this study, we expected that in all the produced copolymers, monomer units would be randomly distributed in heteropolymer chains. In order to evaluate the relationship between the monomer composition and fundamental application-relevant properties of the resulting PHA materials, selected PHA copolymers produced by the strain were solvent-casted onto compact solid films and subjected to complex structural and physicochemical characterization.…”

“…200 • C). However, when other monomer units such as 3-hydroxyvalerate (3HV) or 4-hydroxybutyrate (4HB) are introduced into the polymer chain, the melting temperature as well as the crystallinity of the material are substantially reduced, which is a very positive feature for the processing of the material and ultimately for numerous applications of these polymers [8]. In particular, copolymers containing high fractions of 4HB are considered as auspicious materials for various high-value applications, including but not limited to medicine and the health-care sector [9].…”

Introducing the Newly Isolated Bacterium Aneurinibacillus sp. H1 as an Auspicious Thermophilic Producer of Various Polyhydroxyalkanoates (PHA) Copolymers–1. Isolation and Characterization of the Bacterium

“…For instance, to induce synthesis of polymers containing 3HV subunits, odd carbon number precursors such as n-propanol, propionate, n-pentanol or valerate are applied. Similarly, for production of 4HB-containing polymers, precursor compounds structurally related to 4HB such as 1,4-butanediol, γ-butyrolactone (GBL) or 1,6-hexanediol are utilized [9].…”

Modification of PLA-Based Films by Grafting or Coating

“…Biopolyesters, with poly(lactide) (PLA) as the most prominent representative, are an excellent alternative to fossil-based materials [ 6 , 7 , 8 ]. Sugar-based raw materials like corn and starchcan be used for the production of PLA, which makes it sustainable.…”