Biosynthesis of Poly(3-hydroxyalkanoate) from Amino Acids in Medium with Nitrogen, Phosphate, and Magnesium, or Some Combination of These Nutrients
- 108 Downloads
Twenty natural amino acids were investigated as carbon sources for biosynthesis of poly(3-hydroxyalkanoate) (PHA) by Ralstonia eutropha in media free of inorganic nitrogen, phosphate, or magnesium. First, the effect of limiting nitrogen, phosphate, and magnesium was investigated on the metabolism of l-leucine. Nitrogen-limited media have been widely used to stimulate PHA accumulation, but phosphate-free media lead to higher accumulation. This is because amino acids can act as nitrogen sources, leading to preferential cell growth over PHA accumulation. Magnesium-free conditions don’t show a significant effect on accumulation of PHA. When Ralstonia eutropha was cultivated in the presence of natural amino acids l-leucine, l-isoleucine, l-phenylalanine, and l-tyrosine in media free of nitrogen, phosphate, and magnesium, the PHA content was high, over 40 % of dry weight. Accumulation of PHA on supplementation with mixed substrates of l-leucine and various other amino acids was investigated in nitrogen-, phosphate-, and magnesium-free medium. Culturing with most mixed substrates led to accumulation of PHA, but some led to low or no PHA yield in spite of high PHA yield when metabolized from l-leucine alone. l-cysteine as a sole carbon source showed a unique feature, in that cell growth was significantly preferred over PHA accumulation. A mixed substrate of l-leucine and l-cysteine provided high PHA accumulation because of the combination of PHA accumulation due to l-leucine and cell growth due to l-cysteine. When glucose was used instead of l-leucine in a mixed substrate with l-cysteine, the PHA content was much lower because l-cysteine acts as an inhibitor of glucose metabolism. These results showed that the precise combination of carbon sources is an important factor in accumulation of PHA.
KeywordsBiosynthesis Poly(3-hydroxybutyrate) Amino acid Phosphate-free medium R. eutropha
This work was partially supported by a Grant-in-Aid for Scientific Research, MEXT (No. 24550179). In addition, financial support from a research fund at Ryukoku University is gratefully acknowledged.
- 2.Doi Y, Tamaki A, Kunioka M, Soga K (1987) J Chem Soc Chem Commun 1635Google Scholar
- 10.Zhu C, Nomura CT, Perrotta JA, Stipanovic AJ, Nakas JP (2010) Biotechnol Prog 26:424Google Scholar
- 11.Huijberts GNM, Eggink G, Waard P, Huisman GW, Witholt B (1992) Appl Environ Microbiol 58:536Google Scholar
- 17.Miura T, Ishii D, Nakaoki T (2013) J Polym Environ 21:760Google Scholar
- 23.Anderson AJ, Dawes EA (1990) Microbiol Rev 54:450Google Scholar
- 24.Brandl H, Gross RA, Lenz RW, Fuller RC (1990) Adv Biochem Eng Biotechnol 41:77Google Scholar
- 25.Doi Y (1990) Microbial polyesters. Verlag Chemie, New YorkGoogle Scholar