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. 2024 May 5;16(9):1294.
doi: 10.3390/polym16091294.

Biosynthesis of Polyhydroxyalkanoates in Cupriavidus necator B-10646 on Saturated Fatty Acids

Natalia O Zhila  1   2 , Kristina Yu Sapozhnikova  1   2 , Evgeniy G Kiselev  1   2 , Ekaterina I Shishatskaya  1   2 , Tatiana G Volova  1   2
Affiliations

Biosynthesis of Polyhydroxyalkanoates in Cupriavidus necator B-10646 on Saturated Fatty Acids

Natalia O Zhila et al. Polymers (Basel). .

Abstract

It has been established that the wild-type Cupriavidus necator B-10646 strain uses saturated fatty acids (SFAs) for growth and polyhydroxyalkanoate (PHA) synthesis. It uses lauric (12:0), myristic (14:0), palmitic (16:0) and stearic (18:0) acids as carbon sources; moreover, the elongation of the C-chain negatively affects the biomass and PHA yields. When bacteria grow on C12 and C14 fatty acids, the total biomass and PHA yields are comparable up to 7.5 g/L and 75%, respectively, which twice exceed the values that occur on longer C16 and C18 acids. Regardless of the type of SFAs, bacteria synthesize poly(3-hydroxybutyrate), which have a reduced crystallinity (Cx from 40 to 57%) and a molecular weight typical for poly(3-hydroxybutyrate) (P(3HB)) (Mw from 289 to 465 kDa), and obtained polymer samples demonstrate melting and degradation temperatures with a gap of about 100 °C. The ability of bacteria to assimilate SFAs opens up the possibility of attracting the synthesis of PHAs on complex fat-containing substrates, including waste.

Keywords: PHAs; biosynthesis; degradable polyhydroxyalkanoates; fatty acid mixture; fatty acids; properties.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
The yield of the overall (X, g/L) and residual bacterial biomass (Xres, g/L) (a) and the intracellular PHA content (b) in the culture of the wild-type C. necator B-10646 strain during growth on the saturated FAs of various structures. The letters indicate the significance of the differences when comparing groups according to the Mann–Whitney test at a level of p ≤ 0.05, where identical letters indicate no significant differences.
Figure 2
Figure 2
The scheme of the PHA synthesis from fatty acids: hydrolysis of the triacylglycerols to glycerol and free fatty acids (a) and pathways for the synthesis of PHAs from glycerol and fatty acids (b).
Figure 3
Figure 3
The bacterial biomass yield and intracellular PHA content in the culture of the wild-type C. necator B-10646 strain on the mixtures of fatty acids. The composition of the FA mixtures is detailed in Table 3.
Figure 4
Figure 4
The ratio of the fatty acids in the initial nutrient medium and in the culture of the wild-type bacteria C. necator B-10646 strain at the end of the growth (72 h). The letters indicate the significance of differences when comparing the groups according to a Mann–Whitney test at the level of p ≤ 0.05, where identical letters indicate no significant differences.
Figure 5
Figure 5
The mass spectrum (a) and ion chromatogram (b) of the P(3HB) sample synthesized by the wild-type C. necator B-10646 strain on saturated FAs. The retention time of the 3HB unit is 5.489 min.
Figure 6
Figure 6
GPC chromatogram of the P(3HB) samples synthesized by the wild-type C. necator B-10646 strain on individual saturated FAs (a) and on the mixtures of FAs (b). The composition of FA mixtures corresponds to Table 3.
Figure 7
Figure 7
The temperature characteristics of P(3HB) samples synthesized by the wild-type C. necator B-10646 strain on individual saturated FA–DSC curves (a) and thermal stability (TGA) (b). The temperature characteristics of the P(3HB) samples synthesized on FA mixture–DSC curves (c) and thermal stability (TGA) (d). The numbering of polymer samples corresponds to Table 5.
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