Rodrigues Thomas, Torres Cristiana A V, Marques Susana, Gírio Francisco, Freitas Filomena, Reis Maria A M
Associate Laboratory i4HB, Institute for Health and Bioeconomy, School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal.
UCIBIO-Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal.
Materials (Basel). 2024 Apr 12;17(8):1773. doi: 10.3390/ma17081773.
In recent years, polyhydroxyalkanoates (PHAs) have gained notoriety because of their desirable properties that include proven biodegradability, biocompatibility, and thermal stability, which make them suitable alternatives to fossil-based polymers. However, the widespread use of PHAs is still challenging because of their production costs, which are greatly associated with the cultivation medium used for bacterial cultivation. In Portugal, one-quarter of the forest area is covered by wood, making its residues a cheap, abundant, and sustainable potential carbon source for biotechnological uses. In this work, eucalyptus bark was used as the sole feedstock for PHA production in a circular bioeconomic approach. Eucalyptus bark hydrolysate was obtained after enzymatic saccharification using Cellic CTec3, resulting in a sugar-rich solution containing glucose and xylose. Although with differing performances, several bacteria were able to grow and produce PHA with distinct compositions, using the enzymatic hydrolysate as the sole carbon source. NRRL B-2504 achieved a high cellular growth rate in bioreactor assays (24.4 ± 0.15 g/L) but presented a low accumulation of a medium-chain-length PHA (mcl-PHA) comprising the monomers hydroxydecanoate (HD, 65%), hydroxydodecanoate (HDd, 25%), and hydroxytetradecanoate (HTd, 14%). E264, on the other hand, reached a lower cellular growth rate (8.87 ± 0.34 g/L) but showed a higher biopolymer accumulation, with a polyhydroxybutyrate (PHB) content in the cells of 12.3 wt.%. The new isolate, sp., revealed that under nitrogen availability, it was able to reach a higher accumulation of the homopolymer PHB (31 wt.%). These results, although preliminary, demonstrate the suitability of eucalyptus bark's enzymatic hydrolysate as a feedstock for PHA production, thus offering an exciting avenue for achieving sustainable and environmentally responsible plastic products from an undervalued forestry waste.
近年来，聚羟基脂肪酸酯（PHA）因其具有良好的性能而声名远扬，这些性能包括已被证实的生物可降解性、生物相容性和热稳定性，这使得它们成为化石基聚合物的合适替代品。然而，由于PHA的生产成本与用于细菌培养的培养基密切相关，其广泛应用仍然具有挑战性。在葡萄牙，四分之一的森林面积被木材覆盖，这使得其残留物成为一种廉价、丰富且可持续的潜在生物技术用碳源。在这项工作中，采用循环生物经济方法，将桉树皮用作PHA生产的唯一原料。使用Cellic CTec3进行酶促糖化后获得了桉树皮水解产物，得到了一种富含葡萄糖和木糖的含糖溶液。尽管性能不同，但几种细菌能够利用酶促水解产物作为唯一碳源生长并生产具有不同组成的PHA。NRRL B - 2504在生物反应器试验中实现了较高的细胞生长速率（24.4±0.15 g/L），但中链长度PHA（mcl - PHA）的积累量较低，该mcl - PHA由单体羟基癸酸（HD，65%）、羟基十二烷酸（HDd，25%）和羟基十四烷酸（HTd，14%）组成。另一方面，E264的细胞生长速率较低（8.87±0.34 g/L），但生物聚合物积累量较高，细胞中的聚羟基丁酸酯（PHB）含量为12.3 wt.%。新分离株sp.表明，在有氮的情况下，它能够实现更高的均聚物PHB积累量（31 wt.%）。这些结果虽然是初步的，但证明了桉树皮酶促水解产物作为PHA生产原料的适用性，从而为从被低估的林业废弃物中获得可持续且对环境负责的塑料制品提供了一条令人兴奋的途径。
