Studies on polyhydroxyalkanoates biosynthesis by some Pseudomonas spp. strains

Abstract

Medium-chain-length polyhydroxyalkanoates (mcl-PHAs) are naturally produced by bacteria and accumulates in cytoplasm in the form of granules, in particular culture broth conditions. PHAs are biodegradable, biocompatible and have useful mechanical properties that recommend them for divers applications in various fields. In order to obtain mcl-PHAs of microbial origin we used two Pseudomonas spp. strains, namely Pseudomonas putida ICCF 391 and Pseudomonas fluorescens ICCF 392. Researches have focused the ability of these two strains to use structurally related or not related substrates, to obtain biopolymers with controlled composition, and growth the amount of PHAs in reproducible conditions. Moreover, bioprocess conditions for mcl-PHAs biosynthesis, fermentation broth processing, and polymers composition-were reproducible. As the results achieved with the two strains were similar, researches continued with Pseudomonas fluorescens strain, which is less studied regarding the potential of PHA biosynthesis. Were carried out (co) polymer films containing more than 85% PHO, as determined by GC-FID.

Studies on mcl-Polyhydroxyalkanoates Using Different Carbon Sources for New Biomedical Materials

“…Batch fermentations were performed in 750 mL Erlenmeyer flasks, containing 250 mL of fermentation medium. Bioprocess medium had the following composition in mineral salts: NaNH4HPO4•4H2O 3.5 g/L, K2HPO4 7.5 g/L, KH2PO4 3.7 g/L, structural correlated carbon source (sodium hexanoate, heptanoate, octanoate and nonanoate) 0.835-2.5 g/L, trace element solution I 1.0 mL/L, trace element solution II 1.0 mL/L [12].…”

“…Other environmental factors on which the fermentation medium depends are nature and concentration of the substrate used as carbon and energy source, presence and concentration of other nutrients in the culture medium, temperature, pH, dissolved oxygen concentration, cultivation system. These factors influence the growth rate of the microorganism, cell density at the end of fermentation, substrate grade conversion and intracellular PHA content [3,4]. Depending on the number of carbon atoms, contained by the monomers units, PHAs isolated can be classified as follows: (i) short chain length (scl) PHAs-3 to 5 carbon atoms/monomer, (ii) medium chain length (mcl) PHAs-6 -14 carbon atoms/monomer, and scl-co-mcl with repeat-unit monomers containing 3-14 carbon atoms [2].…”