In an article published on July 2, 2020, in the peer-reviewed journal Biotechnology Advances, Joao Medeiros Garcia Alcantara and colleagues from the Department of Chemistry, Politecnico di Milano, Italy, reviewed the currently available production methods for polyhydroxyalkanoate (PHA) bioplastics.
The authors recall that “PHAs are naturally occurring polymers, mainly produced by bacteria for carbon and energy storage” and that they are “in general . . . biodegradable, biocompatible, non-toxic, insoluble in water and soluble in chloroform and other chlorinated solvents.” However, “depending on the type of PHA, composition and molecular weight, these properties vary greatly, even affecting the degradation kinetics of the material.”
PHA can be produced via three main routes, i.e., microbiological, enzymatic, and chemical. The authors review all three routes focusing on the molecular characteristics of the resulting polymer, costs of raw materials and production processes, and “availability of industrial technologies for large-scale production,” with the final goal being to assess the “potential scalability and current hindrances towards commercialization.”
Based on their findings, the authors conclude that, when considering process costs, “the microbiological route is the one of choice for any possible large-scale production.” The chemical route also presents a favorable possibility, especially considering the availability of industrial technologies for large scale production, while the enzymatic route appears to be the least promising among the three. The cost of the final product still constitutes a major hindrance to the widespread commercialization of PHA bioplastics, because, “even for the most convenient case of the microbiological route, [it] is still too high to compete with that of traditional plastics of fossil origin.” Therefore, current research efforts are “directed to the identification of suitable and cheap raw materials, such as waste streams coming from other industrial or civil activities.” However, “this is only one component of a successful industrial technology,” and “more work needs to be done in the direction of process engineering, for example using . . . integrated continuous production units.”
Medeiros Garcia Alcantara, J., et al. (2020). “Current trends in the production of biodegradable bioplastics: The case of polyhydroxyalkanoates.” Biotechnology Advances 42: 107582.