Abstract
Arctic bacteria employ various mechanisms to survive harsh conditions, one of which is to accumulate carbon and energy inside the cell in the form of polyhydroxyalkanoate (PHA). Whole-genome sequencing of a new Arctic soil bacterium Pseudomonas sp. B14-6 revealed two PHA-production-related gene clusters containing four PHA synthase genes (phaC). Pseudomonas sp. B14-6 produced poly(6% 3-hydroxybutyrate-co-94% 3-hydroxyalkanoate) from various carbon sources, containing short-chain-length PHA (scl-PHA) and medium-chain-length PHA (mcl-PHA) composed of various monomers analyzed by GC-MS, such as 3-hydroxybutyrate, 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxydecanoate, 3-hydroxydodecenoic acid, 3-hydroxydodecanoic acid, and 3-hydroxytetradecanoic acid. By optimizing the PHA production media, we achieved 34.6% PHA content using 5% fructose, and 23.7% PHA content using 5% fructose syrup. Differential scanning calorimetry of the scl-co-mcl PHA determined a glass transition temperature (Tg) of 15.3 °C, melting temperature of 112.8 °C, crystallization temperature of 86.8 °C, and 3.82% crystallinity. In addition, gel permeation chromatography revealed a number average molecular weight of 3.6 × 104, weight average molecular weight of 9.1 × 104, and polydispersity index value of 2.5. Overall, the novel Pseudomonas sp. B14-6 produced a polymer with high medium-chain-length content, low Tg, and low crystallinity, indicating its potential use in medical applications.
Highlights
Some microbes have developed various tactics to survive the harsh Arctic environment [1,2,3]
We previously reported that whole-genome sequencing of Pseudomonas sp
Using the genome sequencing results, we identified two PHA-synthesis-related gene clusters and compared them with PHA-related genes from Ralstonia eutropha, Pseudomonas, and other PHA-producing species by BLAST (Figure 1)
Summary
Some microbes have developed various tactics to survive the harsh Arctic environment [1,2,3] One of these survival mechanisms is to adapt to temperature and nutrition fluctuations by accumulating energy and carbon sources within the cell as polyhydroxyalkanoate (PHA) granules [4,5], which function as chaperone-like molecules to protect internal cellular systems [6,7,8]. PHAs are produced by bacteria using various renewable feedstocks, and are degraded under biological conditions [9] Properties such as the monomer composition, distribution, and molecular weight of these biocompatible polyesters are controlled by different substrates or production hosts [10,11,12]. The production of mcl-PHAs has been relatively challenging due to difficulties in controlling the metabolic flux of the desired monomers [11,19]
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