Polyhydroxyalkanoate (PHA) Biosynthesis from Whey Lactose

The potential of three different microbial wild type strains as polyhydroxyalkanoate (PHA) producers from whey lactose is compared. Homopolyester and co-polyester biosynthesis was investigated by the archaeon Haloferax mediterranei and the eubacterial strains Pseudomonas hydrogenovora and Hydrogenophaga pseudoflava. H. mediterranei accumulated 50 wt.-% of Poly-3-(hydroxybutyrate-co-6%-hydroxyvalerate) in cell dry mass from hydrolyzed whey without addition of 3-hydroxyvalerate (3HV) precursors (specific productivity q(p): 2.9 mg/g h). Using P. hydrogenovora, the final percentage of Poly-3-hydroxybutyrate (PHB) amounted to 12 Wt.-% (q(p): 0.03 g/g h); co-feeding of valeric acid resulted in the production of 12 wt.-%. P-3(HB-CO-21%-HV) (q(p): 0.02 g/g h). With H. pseudoflova, it was possible to reach 40 wt.-% P-3 (HB-CO-5%-HV) on not-hydrolyzed whey lactose plus valeric acid as 3HV precursor (q(p): 9.1 mg/g h); on hydrolyzed whey lactose without addition of valeric acid, the strain produced 30 wt.-% of PHB (q(p): 0.16 g/g h). The characterization of the isolated biopolyesters completes the study.