Sustainable Production of Polyhydroxyalkanoates (PHAs) from Agri-Food Waste: Molecular and Bioengineering Aspects

Polyhydroxyalkanoates (PHAs) are bioplastics fully biodegradable and biocompatible, which can be produced by several bacteria and that exhibit properties like the conventional plastics. PHAs exhibit various applications in the medical field, agro-food, textile, chemical industry, automotive, and others. PHAs are produced in submerged cultures, from batch culture to exponentially fed batch. It is known that pH, oxygen availability, and nutritional conditions affect the concentration and the chemical characteristic of PHAs synthesized by micro-organisms. On the other hand, it has been reported that through manipulation of bacterial metabolism, as well as the culture conditions, it is possible to synthesize biopolymers with specific chemical properties. The production costs of PHAs at a commercial level are highly dependent on the cost of the substrates used for the fermentation process since they represent up to 50% of the global economy of the process. Therefore, several proposals for the use of low-cost raw materials that minimize production costs have been raised. In this chapter, we described the current knowledge about the use of agri-food waste to produce PHAs. The use of these substrates exhibits a high potential, taking into account the economic and environmental aspects. In addition, different fermentation processes with high yields and productivities based on the use of materials from agri-food waste are also included. At the same time, the incorporation of microbial species capable of taking advantage of agro-industrial waste is discussed, and finally, the environmental and economic impact of the production of these biomaterials is analyzed.