Biosynthesis of poly-beta-hydroxyalkanoate by Brevundimonas vesicularis LMG P-23615 and Sphingopyxis macrogoltabida LMG 17324 using acid-hydrolyzed sawdust as carbon source.

Poly-beta-hydroxyalkanoate (PHA) is a biodegradable polymer accumulated in intracellular granules by different bacterial species. Its physical and chemical properties are similar to those of petroleum-derived plastics. Material generated by the acid hydrolysis of wood was evaluated for use in the bacterial synthesis of PHA. Acid-hydrolyzed sawdust was prepared and adjusted to pH 7. Mineral salts with carbon:nitrogen (C:N) proportions of 100:1, 100:3.5, 100:10, 100:30, or 100:50 and trace elements were added and these solutions were inoculated with a bacterial strain Brevundimonas vesicularis LMG P-23615 or Sphingopyxis macrogoltabida LMG 17324. The percentage of cells accumulating PHA was evaluated by flow cytometry. The hydrolyzed sawdust composition was analyzed by gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). The organic material (601.5 mg l(-1)) contained 112.5 mg l(-1) sugars. Over 96% of these sugars were consumed and more than 90% of the bacterial cells accumulated PHA. The 100:3.5 C:N proportion was optimal for growth and PHA synthesis, with yields ranging from 64% to 72% of the dry cell weight. The results suggest that acid-hydrolyzed sawdust can be used by bacteria as a carbon source for growth and PHA production. This forestry by sub-product offers a low-cost alternative for obtaining biodegradable plastics (e.g., PHA) synthesized by bacteria.

Biosynthesis of poly-beta-hydroxyalkanoates by Sphingopyxis chilensis S37 and Wautersia sp. PZK cultured in cellulose pulp mill effluents containing 2,4,6-trichlorophenol.

Poly-beta-hydroxyalkanoates (PHA) polymer is synthesized by different bacterial species. There has been considerable interest in the development and production of biodegradable polymers; however, the high cost of PHA production has restricted its applications. Kraft cellulose industry effluents containing 2,4,6-trichlorophenol (10 or 20 microg ml(-1)) were used by the bacteria Sphingopyxis chilensis S37 and Wautersia sp. PZK to synthesize PHA. In this condition, S. chilensis S37 was able to grow and degrade 2,4,6-trichlorophenol (ca. 60%) and 80% of these cells accumulated PHA. Wautersia PZK completely degraded 2,4,6-TCP and more than 90% of the cells accumulated PHA in 72 h. The PHA detection was performed by flow cytometry and polyester composition was characterized by gas chromatography-mass spectroscopy (GC-MS), indicating that these polymers are made by 3-hydroxybutyric acid and 3-hydroxyhexadecanoic acid for S37 and PZK strains, respectively. Results demonstrated that strains' growth and PHA production and composition are not modified in cellulose effluents with or without 2,4,6-TCP (10-20 microg ml(-1)). Therefore, our results indicate that S. chilensis S37 and Wautersia sp. PZK are able to degrade a toxic compound such as a 2,4,6-TCP and simultaneously produce a valuable biopolymer using low-value substrates.