Plastics such as polyesters are typically produced from petrochemical sources by well-known synthetic means. These petrochemical-based polymers can take centuries to degrade after disposal. Concern over plastic-waste accumulation in landfills has resulted in a recent movement toward using biodegradable polymers instead.
Bio-based biodegradable polymers, also commonly referred to as “bioplastics,” have not enjoyed great success in the marketplace due to their high production cost. However, advances in biotechnology have led to less expensive methods for their production. In one instance, biodegradable aliphatic copolyesters are now often produced by large-scale bacterial fermentation. Collectively termed polyhydroxyalkanoates, also known as “PHAs,” these polymers can be synthesized by a plant or bacteria fed with a particular substrate, such as glucose, in a fermentation plant. In many instances, the structural or mechanical properties of PHAs can be customized to fit the specifications of the desired end product. PHAs can biodegrade both aerobically and anaerobically.
PHAs are enormously versatile, and as many as 100 different PHA structures have been identified. PHA structures can vary in two ways. First, PHAs can vary according to the structure of the pendant groups, which are typically attached to a carbon atom having (D)-stereochemistry. The pendant groups form the side chain of hydroxyalkanoic acid not contributing to the PHA carbon backbone. Second, PHAs can vary according to the number and types of their repeat units. For example, PHAs can be homopolymers, copolymers, or terpolymers. These variations in PHA structure can cause variations in their physical characteristics. These physical characteristics make PHAs useful for a number of products that may be commercially valuable.
However, in order to have any type of commercially marketable PHA bioplastic product, there is a need for an efficient process for separating such PHAs from the residual biomass.
Numerous solvent-based and other types of extraction techniques are known in the art for extracting PHAs from a biomass. Solvent-based systems (including those utilizing ketones, toluene, alcohols, alone and in combination with other solvents), mechanical systems, and combinations thereof may be used for extracting PHA.
Typically the solubility of the polymer is not high enough to make it economical. Therefore, there is a need for a more efficient and cost-saving process to load more polymer into the organic solvent for extracting the PHA materials from biomass.