White Biotechnology for Biopolymers

Poly(hydroxyalkanoates): Production, Applications and End-of-Life Strategies–Life Cycle Assessment Nexus

“…PHAs are mostly found in the cytoplasm of bacteria as high molecular weight intracellular granules with diameters ranging from 0.2 to 0.7 μm. , In 1926, the first PHA polymer known as polyhydroxybutyrate (PHB) was isolated by a French researcher, M. Lemoigne, while experimenting on Bacillus megaterium . , This important polymer exhibited a high melting temperature of 175 °C, high crystallinity, and high tensile strength (30–35 MPa) . After this discovery, more than 150 different hydroxy-acid monomer structures have been reported to date. , Figure a shows the general structure of PHA, whereas Figure b portrays some PHA family members, namely, 3HB (3-hydroxybutyrate), 3HV (3-hydroxyvalerate), 3HHx (3-hydroxyhexanoate), 3HO (3-hydroxyoctanoate), 3HD (3-hydroxydecanoate), and 3HDD (3-hydroxydodecanoate) …”

“…(a) Structure of PHA and (b) PHA family members. Reproduced with permission from ref . Copyright 2015 Elsevier.…”

“…The PHA family of monomer structures mainly exists in two types depending on the 3-hydroxyalkanoate units present: (i) short-chain-length (scl, C3–C5) and (ii) medium-chain-length (mcl, C6–C14) chains as shown in (Figure b) . These varieties of PHAs are formed from the general structure, depending not only on the structure and length of the main chain but also on the PHA pendant chains.…”

“…From the traditional microbiological synthesis route of PHA production and other techniques such as in vitro enzymatic synthesis and ring-opening polymerization (ROP), major issues, especially high production costs of polyhydroxyalkanoates (PHAs), must be solved first . This demands for a changeover from the costly traditional fermentation technique known as conventional industrial biotechnology (CIB) to the industrial biotechnology of the future, referred to as next generation industrial biotechnology (NGIB) . Now that the PHAs derived from conventional industrial biotechnology (CIB) techniques are still more costly than standard oil-based polymers due to the process inefficiencies and purified substrates involved, new production methods must be explored .…”

“…Now that the PHAs derived from conventional industrial biotechnology (CIB) techniques are still more costly than standard oil-based polymers due to the process inefficiencies and purified substrates involved, new production methods must be explored . In order to explore new avenues of PHA production, a cost study and process economics of the PHA production chain utilizing the CIB chassis has revealed that the overall high cost is mainly due to fermentation sterilizing expenses, massive volumes of freshwater required, high energy, batch-wise operations, and the high cost of substrates . PHA has a production cost that is 5–6 times that of other plastics; thus, it cannot compete advantageously in the global plastics market. , In this context, researchers have looked for alternate PHA manufacturing routes to lower the prohibitive PHA cost.…”