Bacterial Poly(hydroxyalkanoates) as a Source of Chiral Hydroxyalkanoic Acids

Abstract

Polyhydroxyalkanoates (PHA) are polyesters of various hydroxyalkanoates accumulated in numerous bacteria. All of the monomeric units of PHA are enantiomerically pure and in R-configuration. R-Hydroxyalkanoic acids can be widely used as chiral starting materials in fine chemical, pharmaceutical and medical industries. In this study, we established an efficient method for the production of chiral hydroxyalkanoic acid monomers from PHA. Pseudomonas putida cells containing PHA were resuspended in phosphate buffer at different pH. We observed that the optimal initial pH for intracellular PHA degradation and monomer release was at pH 8-11 with pH 11 as the best. At initial pH 11, PHA containing 3-hydroxyoctanoic acid and 3-hydroxyhexanoic acid was degraded with an efficiency of over 90% (w/w) in 9 h, and the yield of the corresponding monomers was also over 90%. Under the same conditions, unsaturated monomers were also effectively produced from PHA containing 3-hydroxy-6-heptenoic acid, 3-hydroxy-8-nonenoic acid, and 3-hydroxy-10-undecenoic acid. The monomers (e.g., 3-hydroxyoctanoic acid) were further isolated using solid phase extraction and purified on reversed phase semipreparative liquid chromatography. We confirmed that the purified 3-hydroxyoctanoic acid monomer has exclusively the R-configuration.

Poly(3-Hydroxybutyrate) (PHB) Depolymerase PhaZa1 Is Involved in Mobilization of Accumulated PHB in Ralstonia eutropha H16

“…Based on reports that the in vivo hydrolysis of PHA and the secretion of 3-hydroxyalkanoic acids by different bacteria can be efficient at a pH level of 10 to 11 (30,42) or at a pH level of 3 to 4 (24), cells were washed to limit the source of secreted 3HB to intracellularly accumulated PHB and resuspended in the same volume of 0.1 M of potassium phosphate buffer (pH 7), morpholineethanesulfonic acid-NaOH buffer (pH 4), or Tris-HCl buffer (pH 10). After cell-free samples were incubated at 30°C, they were analyzed for secreted 3HB.…”

Whey Lactose as a Raw Material for Microbial Production of Biodegradable Polyesters

“…After the release from cells, they can be processed to a marketable form, e.g. to granulates, and used as sustainable biodegradable substitutes for a variety of "classical" petrochemical plastics such as poly(ethylene) (PE), poly(propylene) (PP), poly(ethlyleneterephtalate) (PET) and many others (Reddy et al, 2003;Khanna & Srivastava, 2005;Ren et al, 2005;Chen, 2009). According to calculations accomplished by Akiyama et al (2003), Harding et al (2007), Pietrini et al (2007), and Titz et al (2012), the production of PHAs should be more beneficial if considering full cradle-to-gate life cycle analysis (LCA) than the production of the petrochemical plastics mentioned before.…”

“…Hydrolysis of PHA to the monomers generally results in a rich source of chiral synthons that can be used as starting materials for synthesis of fine chemicals and marketable products such as pheromons, aromatics, vitamins or antibiotics, or can even be used as pharmaceutically active compounds (Ren et al, 2005). It was demonstrated that 3HB and its oligomers reveal therapeutic effects.…”

Non-Edible Vernonia galamensis Oil and Mixed Bacterial Cultures for the Production of Polyhydroxyalkanoates

“…Although these substrates have generated PHA contents of 48 to 77% of cell dry weight (cdw), they are costly, edible and are therefore not competitive for industrial-scale production of PHA [8][9][10][11]. With high gross operating expenses and the resulting cost of PHA at ca.…”