Jha Amit K, Martinez Daniella V, Martinez Estevan J, Salinas Jay E, Kent Michael S, Davydovich Oleg
Bioresource and Environmental Security, Sandia National Labs, Livermore, CA, USA.
Department of Environmental System Biology, Sandia National Labs, Albuquerque, NM, USA.
J Ind Microbiol Biotechnol. 2024 Jan 9;51. doi: 10.1093/jimb/kuae050.
There is a growing interest in developing a methodology for effectively cleaving carbon-carbon (C-C) bonds in polymer backbones through bioconversion processes that utilize microorganisms and their enzymes. This upsurge of interest is driven by the goal of achieving a circular economy. Polyolefin post-consumer plastics are a substantial source of carbon, but the recycling potential is severely limited. Upcycling routes are needed for converting polyolefin post-consumer plastics into value-added products while concurrently mitigating adverse environmental effects. These materials contain carbon-based chemicals that can, in principle, serve as the feedstock for microbial metabolism. Some microbes have been reported to grow on polyolefin plastics, but the rate of biodegradation is insufficient for industrial processes. In this study, low-density polyethylene (LDPE) films were subjected to two mild ozone-based oxidation treatments, which facilitated biodegradation. The degree of oxidation was determined by Fourier transform infrared spectroscopy via analysis of the carbonyl index (1,710/1,460 cm-1), which ranged from 0.3 to 2.0, and also via analysis of the carboxylic acid content. Following oxidation of the films, studies were conducted to investigate the ability of a panel of polyvinyl alcohol-degrading microbes to degrade the oxidized films. A defined minimal medium was used to cultivate and assess microbial growth on the oxidized films. Following 45 days of cultivation, the most effective strains were further cultivated up to three additional generations on the oxidized film substrates to improve their ability to degrade the oxidized LDPE films. After these enrichments, we identified a strain from the third generation of Pseudomonas sp. Rh926 that exhibited significant cell growth and reduced the oxidized LDPE film mass by 25% in 30 days, demonstrating an enhanced capacity for degrading the oxidized LDPE films.
ONE-SENTENCE SUMMARY: Discovery and adaptation techniques were used to enhance the metabolic capability of microorganisms for increased biodegradation of ozone-oxidized LDPE films as a step toward a future upcycling process.
人们越来越有兴趣开发一种方法，通过利用微生物及其酶的生物转化过程，有效裂解聚合物主链中的碳 - 碳（C - C）键。这种兴趣的高涨是由实现循环经济的目标驱动的。聚烯烃消费后塑料是大量的碳源，但回收潜力严重受限。需要升级回收路线，将聚烯烃消费后塑料转化为增值产品，同时减轻不利的环境影响。这些材料含有碳基化学品，原则上可作为微生物代谢的原料。据报道，一些微生物能在聚烯烃塑料上生长，但生物降解速率不足以用于工业过程。在本研究中，低密度聚乙烯（LDPE）薄膜经过两种基于臭氧的温和氧化处理，这促进了生物降解。氧化程度通过傅里叶变换红外光谱法，通过分析羰基指数（1710/1460 cm⁻¹）来确定，其范围为0.3至2.0，也通过分析羧酸含量来确定。薄膜氧化后，进行研究以调查一组聚乙烯醇降解微生物降解氧化薄膜的能力。使用确定的基本培养基在氧化薄膜上培养和评估微生物生长。培养45天后，将最有效的菌株在氧化薄膜底物上进一步培养多达三代，以提高它们降解氧化LDPE薄膜的能力。经过这些富集培养后，我们从第三代假单胞菌属中鉴定出一株Rh⁹²⁶菌株，该菌株在30天内表现出显著的细胞生长，并使氧化LDPE薄膜质量减少了25%，证明其降解氧化LDPE薄膜的能力增强。
采用发现和适应技术来增强微生物的代谢能力，以增加对臭氧氧化的LDPE薄膜的生物降解，作为迈向未来升级回收过程的一步。
