Koller Martin, Mukherjee Anindya
Office of Research Management and Service, c/o Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28/IV, 8010 Graz, Austria.
ARENA-Association for Resource Efficient and Sustainable Technologies, Inffeldgasse 21b, 8010 Graz, Austria.
Bioengineering (Basel). 2022 Feb 15;9(2):74. doi: 10.3390/bioengineering9020074.
The ever-increasing use of plastics, their fossil origin, and especially their persistence in nature have started a wave of new innovations in materials that are renewable, offer the functionalities of plastics, and are biodegradable. One such class of biopolymers, polyhydroxyalkanoates (PHAs), are biosynthesized by numerous microorganisms through the conversion of carbon-rich renewable resources. PHA homo- and heteropolyesters are intracellular products of secondary microbial metabolism. When isolated from microbial biomass, PHA biopolymers mimic the functionalities of many of the top-selling plastics of petrochemical origin, but biodegrade in soil, freshwater, and marine environments, and are both industrial- and home-compostable. Only a handful of PHA biopolymers have been studied in-depth, and five of these reliably match the desired material properties of established fossil plastics. Realizing the positive attributes of PHA biopolymers, several established chemical companies and numerous start-ups, brand owners, and converters have begun to produce and use PHA in a variety of industrial and consumer applications, in what can be described as the emergence of the "PHA industry". While this positive industrial and commercial relevance of PHA can hardly be described as the first wave in its commercial development, it is nonetheless a very serious one with over 25 companies and start-ups and 30+ brand owners announcing partnerships in PHA production and use. The combined product portfolio of the producing companies is restricted to five types of PHA, namely poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxybutyrate--3-hydroxyvalerate), poly(3-hydroxybutyrate--4-hydroxybutyrate), and poly(3-hydroxybutyrate--3-hydroxyhexanoate), even though PHAs as a class of polymers offer the potential to generate almost limitless combinations of polymers beneficial to humankind. To date, by varying the co-monomer type and content in these PHA biopolymers, their properties emulate those of the seven top-selling fossil plastics, representing 230 million t of annual plastics production. Capacity expansions of 1.5 million t over the next 5 years have been announced. Policymakers worldwide have taken notice and are encouraging industry to adopt biodegradable and compostable material solutions. This wave of commercialization of PHAs in single-use and in durable applications holds the potential to make the decisive quantum leap in reducing plastic pollution, the depletion of fossil resources, and the emission of greenhouse gases and thus fighting climate change. This review presents setbacks and success stories of the past 40 years and the current commercialization wave of PHA biopolymers, their properties, and their fields of application.
塑料的使用日益增加，其源自化石，尤其是在自然界中具有持久性，这引发了一波材料创新浪潮，这些材料可再生，具备塑料的功能且可生物降解。一类这样的生物聚合物，即聚羟基脂肪酸酯（PHA），是由众多微生物通过将富含碳的可再生资源进行转化而生物合成的。PHA均聚物和共聚物是微生物二次代谢的细胞内产物。当从微生物生物质中分离出来时，PHA生物聚合物模仿了许多畅销的石化源塑料的功能，但在土壤、淡水和海洋环境中可生物降解，并且在工业和家庭堆肥中均可降解。只有少数几种PHA生物聚合物得到了深入研究，其中有五种能够可靠地匹配现有化石塑料所需的材料性能。认识到PHA生物聚合物的积极特性后，几家老牌化工公司以及众多初创企业、品牌所有者和加工商已开始在各种工业和消费应用中生产和使用PHA，这可以说是“PHA产业”的兴起。虽然PHA在工业和商业上的这种积极关联很难说是其商业发展的第一波浪潮，但它仍然是非常重要的一波，有超过25家公司和初创企业以及30多家品牌所有者宣布在PHA的生产和使用方面建立合作关系。生产公司的联合产品组合仅限于五种类型的PHA，即聚（3 - 羟基丁酸酯）、聚（4 - 羟基丁酸酯）、聚（3 - 羟基丁酸酯 - 3 - 羟基戊酸酯）、聚（3 - 羟基丁酸酯 - 4 - 羟基丁酸酯）和聚（3 - 羟基丁酸酯 - 3 - 羟基己酸酯），尽管PHA作为一类聚合物有潜力产生几乎无限的对人类有益的聚合物组合。迄今为止，通过改变这些PHA生物聚合物中的共聚单体类型和含量，它们的性能可模拟七种畅销化石塑料的性能，这些化石塑料的年产量达2.3亿吨。已宣布在未来5年内产能将扩大150万吨。全球政策制定者已予以关注，并鼓励行业采用可生物降解和可堆肥的材料解决方案。PHA在一次性和耐用应用中的这一波商业化浪潮有可能在减少塑料污染、化石资源枯竭以及温室气体排放从而应对气候变化方面实现决定性的重大飞跃。本综述介绍了过去40年的挫折与成功案例以及当前PHA生物聚合物的商业化浪潮、它们的性能及其应用领域。
