Polyhydroxyalkanoates Production: A Challenge for the Plastic Industry

Abstract

The accumulation of petroleum-based plastics in the environment has heightened the necessity of finding alternative materials with similar properties and lower environmental impact. Polyhydroxyalkanoates (PHAs) are a group of naturally occurring polyesters that have been investigated for several decades as potential substitutes for commonly used plastics. PHAs are biodegradable and biocompatible polymers derived from renewable resources. From this point of view, their industrial implementation represents an attractive strategy to reduce plastic pollution and petroleum dependency. Nevertheless, the high production costs related to these materials have considerably hindered their broader use and commercialization. In this regard, several approaches have been proposed to turn their production competitive from a commercial perspective. For instance, several studies have scrutinized the different production steps of PHAs in terms of economic viability. Reported strategies include optimization of fermentation processes; selection, isolation, and genetic modification of microbial strains; selection of low-cost renewable raw materials; and more efficient separation processes of the produced PHAs. This review summarizes the main advantages and disadvantages of different strategies proposed to improve the competitiveness of PHAs production; potential applications of PHAs manufactured by these different methods, as well as the main challenges to be overcome to develop economically viable industrial processes, are discussed in detail.

Bioplastic Production from Agri-Food Waste through the Use of Haloferax mediterranei: A Comprehensive Initial Overview

“…The natural variability found in these matrices, moreover, represents an additional critical issue for the standardization of the downstream processes aiming at recovering and purifying PHAs. Indeed, it has been reported that changes in the C:N ratios of the substrates led to variations in polymer accumulation, thus requiring a continuous adaptation of the purification protocol [ 9 ]. In particular, the molar mass of the polymer strongly affects its technological properties, thus making the control of the biosynthesis fundamental from the early fermentation stage.…”

“…If high-purity PHAs are required, the use of chlorinated solvents or acetone in the extraction and purification stages is required. Enzymatic treatment, chemical treatments with sodium hypochlorite or surfactants, and mechanical disruption are other downstream processing methods that are available [ 9 ]. It must be considered that the purification processes translate into additional demands for energy and chemical substances, which negatively affect the costs and sustainability of bioplastic production.…”

“…It must be considered that the purification processes translate into additional demands for energy and chemical substances, which negatively affect the costs and sustainability of bioplastic production. Substantial improvements in the purification processes for PHAs have been recognized as the key to improving the market competitiveness of these polymers [ 9 , 44 ]. In downstream processing, haloarchaea present advantageous features related to their adaptability to extreme salinity.…”

“…The bioplastic market is constantly growing. In 2010, 0.7 million tons of bioplastics were produced, versus 1.7 million tons in 2015 [ 8 ], and it has been estimated that annual bioplastic production will reach 3 million tons in 2025 [ 9 ]. Bioplastics’ advantages are multiple, including a reduction in fossil resource use, CO 2 impact, and non-degradable plastic waste.…”

“…Recent research has examined biotechnological applications, such as the identification of optimal fermentation conditions for microorganisms to produce PHA [ 4 , 9 , 12 ]. Currently, there is significant interest in reviewing the application of low-cost substrates as a source of nutrients for microbial growth and precursors to bioplastic production.…”