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Biosynthesis of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from CO2 by a Recombinant Cupriavidusnecator

Bioengineering 2021 50 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count. Score: 45 ? 0–100 AI score estimating relevance to the microplastics field. Papers below 30 are filtered from public browse.
Kenji Tanaka, Kazumasa Yoshida, Izumi Orita, Toshiaki Fukui

Summary

A recombinant Cupriavidus necator strain was engineered to produce the flexible, marine-biodegradable copolyester PHBHHx from CO2 as the sole carbon source, demonstrating a route to bio-based plastic production that avoids competition with food crops for feedstocks.

The copolyester of 3-hydroxybutyrate (3HB) and 3-hydoxyhexanoate (3HHx), PHBHHx, is one of the most practical kind of bacterial polyhydroxyalkanoates due to its high flexibility and marine biodegradability. PHBHHx is usually produced from vegetable oils or fatty acids through β-oxidation, whereas biosynthesis from sugars has been achieved by recombinant strains of hydrogen-oxidizing bacterium Cupriavidus necator. This study investigated the biosynthesis of PHBHHx from CO2 as the sole carbon source by engineered C. necator strains. The recombinant strains capable of synthesizing PHBHHx from fructose were cultivated in a flask using complete mineral medium and a substrate gas mixture (H2/O2/CO2 = 8:1:1). The results of GC and 1H NMR analyses indicated that the recombinants of C. necator synthesized PHBHHx from CO2 with high cellular content. When 1.0 g/L (NH4)2SO4 was used as a nitrogen source, the 3HHx composition of PHBHHx in the strain MF01∆B1/pBBP-ccrMeJ4a-emd was 47.7 ± 6.2 mol%. Further investigation demonstrated that the PHA composition can be regulated by using (R)-enoyl-CoA hydratase (PhaJ) with different substrate specificity. The composition of 3HHx in PHBHHx was controlled to about 11 mol%, suitable for practical applications, and high cellular content was kept in the strains transformed with pBPP-ccrMeJAc-emd harboring short-chain-length-specific PhaJ.

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