Jeon Jong-Min, Brigham Christopher J, Kim Yong-Hyun, Kim Hyun-Joong, Yi Da-Hye, Kim Hyungsup, Rha ChoKyun, Sinskey Anthony J, Yang Yung-Hun
Department of Microbial Engineering, College of Engineering, Konkuk University, Seoul, South Korea.
Appl Microbiol Biotechnol. 2014 Jun;98(12):5461-9. doi: 10.1007/s00253-014-5617-7. Epub 2014 Mar 11.
Polyhydroxyalkanoates (PHAs), a promising family of bio-based polymers, are considered to be alternatives to traditional petroleum-based plastics. Copolymers like poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P(HB-co-HHx)) have been shown to exhibit favorable physical and mechanical properties, due to decreased crystallinity resulting from the presence of medium-chain-length 3-hydroxyhexanoate (3HHx) monomers. In this study, we produced P(HB-co-HHx) using engineered Ralstonia eutropha strains containing deletions of the acetoacetyl-CoA reductase (phaB) genes and replacing the native PHA synthase with phaC2 from Rhodococcus aetherivorans I24 and by using butyrate, a short-chain organic acid, as the carbon source. Although the wild-type R. eutropha did not produce P(HB-co-HHx) when grown on mixed acids or on butyrate as the sole carbon source, we are able to produce polymer containing up to 40 wt% 3HHx monomer with the aforementioned engineered R. eutropha strains using various concentrations of just butyrate as the sole carbon source. This is the first report for the production of P(HB-co-HHx) copolymer in R. eutropha using butyrate.
聚羟基脂肪酸酯（PHA）是一类很有前景的生物基聚合物，被认为是传统石油基塑料的替代品。像聚（3-羟基丁酸酯-co-3-羟基己酸酯）（P(HB-co-HHx)）这样的共聚物，由于中链长度的3-羟基己酸酯（3HHx）单体的存在导致结晶度降低，已显示出良好的物理和机械性能。在本研究中，我们使用了工程改造的真养产碱杆菌菌株来生产P(HB-co-HHx)，这些菌株缺失了乙酰乙酰辅酶A还原酶（phaB）基因，并用来自食醚红球菌I24的phaC2替代了天然的PHA合酶，同时使用短链有机酸丁酸盐作为碳源。虽然野生型真养产碱杆菌在混合酸或丁酸盐作为唯一碳源生长时不产生P(HB-co-HHx)，但我们能够使用各种浓度的丁酸盐作为唯一碳源，用上述工程改造的真养产碱杆菌菌株生产出含高达40 wt% 3HHx单体的聚合物。这是关于在真养产碱杆菌中使用丁酸盐生产P(HB-co-HHx)共聚物的首次报道。
