Production of poly-beta-hydroxybutyrate (PHB) by Alcaligenes latus from maple sap.

Maple sap, an abundant natural product especially in Canada, is rich in sucrose and thus may represent an ideal renewable feedstock for the production of a wide variety of value-added products. In the present study, maple sap or sucrose was employed as a carbon source to Alcaligenes latus for the production of poly-beta-hydroxybutyrate (PHB). In shake flasks, the biomass obtained from both the sap and sucrose were 4.4 +/- 0.5 and 2.9 +/- 0.3 g/L, and the PHB contents were 77.6 +/- 1.5 and 74.1 +/- 2.0%, respectively. Subsequent batch fermentation (10 L sap) resulted in the formation of 4.2 +/- 0.3 g/L biomass and a PHB content of 77.0 +/- 2.6%. The number average molecular weights of the PHB produced by A. latus from maple sap and pure sucrose media were 300 +/- 66 x 10(3) and 313 +/- 104 x 10(3) g/mol, respectively. Near-infrared, (1)H magnetic resonance imaging (MRI), and (13)C-MRI spectra of the microbially produced PHB completely matched those obtained with a reference material of poly[(R)-3-hydroxybutyric acid]. The polymer was found to be optically active with [alpha](25) (D) equaled to -7.87 in chloroform. The melting point (177.0 degrees C) and enthalpy of fusion (77.2 J/g) of the polymer were also in line with those reported, i.e., 177 degrees C and 81 J/g, respectively.

Microbial resolution of baclofen by a new isolate of Streptomyces halstedii.

We attempted to isolate microorganisms able to metabolize (S)-baclofen while showing little or no activity with (R)-baclofen. A culture collection of 218 microbial isolates was established from several soil samples using various approaches. Subsequent chiral HPLC analysis revealed that only two cultures showed promise. Initial shake flask experiments demonstrated a correlation between culture growth and (S)-baclofen metabolism. (S)-baclofen was metabolized much more rapidly than (R)-baclofen. The best culture, identified as Streptomyces halstedii, was used to scale up the process in small-scale fed-batch fermentations using pulse addition of racemic baclofen to yield extracellular fractions showing enantiomeric excess (e.e.) values of greater than 90% in favour of the (R)-isomer. Resting cells also were able to carry out the wanted reaction but initial attempts using cell free extracts were negative. It is speculated that the initial attack on (S)-baclofen may be catalyzed by a mono- or dioxygenase.