Review of Polyhydroxyalkanoates and Their Synthesis and Identification Methods from Microorganisms

The harmful effects of synthetic plastics and their products have become a significant concern for researchers. Bioplastics or plastics produced by microorganisms are promising alternatives to conventional synthetic plastics. Polyhydroxyalkanoates (PHAs) are biopolyesters known as biodegradable and biologically produced materials with properties similar to conventional plastics, produced by various microorganisms from renewable resources such as carbohydrates, lipids, alcohols, or organic acids under unfavorable growth conditions due to nutrient imbalance, and accumulated as storage granules in the cytoplasm of microorganisms. Bioplastics are a new generation family of biodegradable plastics with various applications. Bioplastics are an eco-friendly alternative to plastics, degraded by microbial enzymes into CO۲, methane, H۲O, and biodegradable biomass. Although the production of bioplastics reduces fossil fuel consumption and CO۲ emissions and decreases plastic waste generation, the high cost of producing bioplastics from bacteria remains a major limitation compared to the cost of producing petroleum-derived polymers. However, over the next decade, bioplastics are expected to account for ۳۰% of the total plastics market. Polyhydroxyalkanoates are categorized into three main types based on the number of carbon atoms in their monomer units: short-chain, medium-chain, and long-chain PHAs. Over ۳۰۰ species of bacteria, including Gram-positive bacteria, Gram-negative bacteria, photosynthetic archaebacteria like cyanobacteria, marine bacteria, and several recombinant bacteria and plants, have been reported as PHA producers. Synthetic plastics are currently considered an essential need for human life, but unfortunately, they are non-biodegradable, causing environmental pollution. Moreover, recycled plastics create more environmental issues compared to bioplastics due to the mixing of additives, dyes, and stabilizers. Due to environmental and waste management problems, bioplastics have become a substitute for plastics. This review article discusses the types of PHAs, their biosynthesis methods and characteristics, as well as the main PHA-producing strains, including Gram-positive bacteria, Gram-negative bacteria, microalgae, archaea, recombinant bacteria, cyanobacteria, and eukaryotes. Various identification methods such as Sudan black staining, FTIR analysis, and PCR are also reviewed.

کلیدواژه ها:

Polyhydroxyalkanoate (PHA) ، Gram-positive bacteria ، Gram-negative bacteria ، photosynthetic archaebacteria ، cyanobacteria ، marine bacteria ، recombinant plants ، FTIR analysis ، PCR ، CO۲ ، fossil fuel ، petroleum