From Microbical Biopolymers to Bioplastics: Sustainable Additives for PHB Processing and Stabization

The term biopolymers refers to a broad class of materials that derive from naturally occurring resources. Biopolymers can be obtained through extraction from biomasses, but also through chemical or biotechnological methods from raw natural substrates. They are used to produce bioplastics, which could substitute fossil fuel-derived commodities. Among them, polyhydroxyalkanoates (PHAs) are polyesters synthesized by microorganisms as energy reserve. The most important member of PHA family is poly(3-hydroxybutyrate) (PHB). PHB is mechanically similar to polypropylene, even though its thermal instability, brittleness, and stiffness hinder its applicability. Improving PHB physical properties can be achieved by blending it with natural additives or by-products of industrial processes. This work takes the form of a case study about the effects of three natural, phenol-based, and polysaccharidic compounds on PHB properties. In particular, data on blending of two PHB matrices with a grape pomace extract (EP), a lignocellulosic biomass (LC), and tannic acid (TA) are reported. The preparation and characterization of PHB compounds and the effects of the additives on processing, thermal and photooxidative stability, crystallization rate, and microbial digestion of PHB are also shown. An overall improvement of polymer processability and photostability, along with changes in crystallization rates, was observed. The study provides evidence that natural additives have the potential for promoting the transition from biopolymers to bioplastics in a sustainable way, both from an environmental and economical point of view.