PHA-Based Bioplastic: a Potential Alternative to Address Microplastic Pollution

Abstract

Petroleum-derived plastics are linked to a variety of growing environmental issues throughout their lifecycle, including emission of greenhouse gases, accumulation in terrestrial and marine habitats, pollution, among others. There has been a lot of attention over the last decade in industrial and research communities in developing and producing eco-friendly polymers to deal with the current environmental issues. Bioplastics preferably are a fast-developing family of polymeric substances that are frequently promoted as substitutes to petroleum-derived plastics. Polyhydroxyalkanoates (PHAs) have a number of appealing properties that make PHAs a feasible source material for bioplastics, either as a direct replacement of petroleum-derived plastics or as a blend with elements derived from natural origin, fabricated biodegradable polymers, and/or non-biodegradable polymers. Among the most promising PHAs, polyhydroxybutyrates (PHBs) are the most well-known and have a significant potential to replace traditional plastics. These biodegradable plastics decompose faster after decomposing into carbon dioxide, water, and inorganic chemicals. Bioplastics have been extensively utilized in several sectors such as food-processing industry, medical, agriculture, automobile industry, etc. However, it is also associated with disadvantages like high cost, uneconomic feasibility, brittleness, and hydrophilic nature. A variety of tactics have been explored to improve the qualities of bioplastics, with the most prevalent being the development of gas and water barrier properties. The prime objective of this study is to review the current knowledge on PHAs and provide a brief introduction to PHAs, which have drawn attention as a possible potential alternative to conventional plastics due to their biological origin, biocompatibility, and biodegradability, thereby reducing the negative impact of microplastics in the environment. This review may help trigger further scientific interest to thoroughly research on PHAs as a sustainable option to greener bioplastics.

Keywords: Bioplastics; Microplastics; Polyhydroxyalkanoates (PHAs); Polyhydroxybutyrates (PHBs).

Fig. 1

a Pie chart of global distribution of plastics in various sectors (Statista, 2021) and b Pie chart of global plastic waste management before recycling, 2019 (OECD, 2022)

Fig. 2

Schematic illustration of the different occurrences and pathways of MPs (modified from Picó & Barceló, 2019)

Fig. 3

An illustration of the mechanisms behind plastic deterioration (modified from Zhang et al., 2021)

Fig. 4

Effect of microplastics in aquatic environment (modified from Issac and Kandasubramanian, 2021)

Fig. 5

Effect of microplastics to plants and organisms that live in soil (modified from Khalid et al., 2020)

Fig. 6

Schematic representation of airborne microplastics being deposited into global biosphere (modified from Shao et al., 2022)

Fig. 7

Exposure route of microplastics to human body and its associated effects (modified from Ageel et al., ; Bhuyan, 2022)

Fig. 8

General structure of PHAs and some of its polymers (modified from Akinmulewo & Nwinyi, 2019)

Fig. 9

Biochemical mechanism for PHB production. a Schematic diagram showing metabolic pathway of PHB production. b Schematic diagram showing metabolic pathway of PHB production along with its chemical structure (modified from Ross et al., 2017)

Fig. 10

Applications of PHAs Biopolymers (modified from Abd El-malek et al., 2020)