Research articles
ScienceAsia 51S (2025):ID 2025s019 1-10 |doi:
10.2306/scienceasia1513-1874.2025.s019
Engineering of β-oxidation pathway to tailor
polyhydroxyalkanoate (PHA) production in Bacillus
thermoamylovorans
Atitiya Kruaejuna, Thanaphorn Rakkana,b, Nisa Paichidc, Kanokphorn Sangkharakc,d,*
ABSTRACT: Polyhydroxyalkanoate (PHA) is a type of microbial polyester that is stored within cells as a carbon and
energy source. This study evaluated the effects of knockout gene mutation on the production and modification of PHA
in Bacillus thermoamylovorans. The genes fadB and fadA, which encode 3-ketoacyl-CoA thiolase and 3-hydroxyacyl-CoA
dehydrogenase, respectively, in B. thermoamylovorans were deleted to suppress the ?-oxidation pathway. The potential
of the wildtypeandmutanttoproducePHAundervariousfattyacidswassubsequentlystudied. Thewildtypeproduced
the highest biomass and PHA content, measuring 4.5?0.3 g/l and 41.4?1.0%, respectively, when grown on sodium
octanoate. The similar pattern was observed in mutant strain, which yielded 3.8?0.2 g/l of biomass and 41.0?1.0%
PHAunderthe samecondition. In addition, heterogeneous PHA was detected in both the wild-type and mutant strains.
These findings indicate that fadB and fadA are crucial for fatty acid degradation. However, deleting fadB and fadA did
not negatively affect biomass or PHA production. Furthermore, the production of PHA was scaled up in a 3-l fermenter.
Highvalues of thespecific growthrate, biomass productivity, and maximumproductivity were detected in the wild-type.
Interestingly, the mutant strain produced medium-co-long-chain-length (mcl-co-lcl) PHA, whereas the wild-type strain
primarily synthesized short-chain-length (scl) PHA. Compared with scl-PHA, mcl-PHA is more advantageous because
of its superior elasticity, reduced crystallinity and tensile strength, and elevated melting point. This study represents
the first report of enhanced PHA production in B. thermoamylovorans through knockout of the fadB and fadA genes.
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| a |
Biotechnology Program, Department of Biological, Faculty of Science and Digital Innovation, Thaksin University,
Phatthalung 93210 Thailand |
| b |
Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 Thailand |
| c |
Innovative Material Chemistry for Environment Center, Department of Chemistry, Faculty of Science and Digital
Innovation, Thaksin University, Phatthalung 93210 Thailand |
| d |
Faculty of Agricultural Technology, Phuket Rajabhat University, Phuket 83000 Thailand |
* Corresponding author, E-mail: kanokphorn.s@pkru.ac.th
Received 28 Nov 2024, Accepted 0 0000
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