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.
The aim of this comparative study was to obtain a model for production of inulinase and invertase by species Saccharomyces, Candida and Hansenula, strains from culture collection of INCDCF-ICCF, using submerged fermentation in a medium containing inulin as source of C. This model explained the data variation and the actual relationships between the parameters and responses. The dry biomass content as well as the production of inulinase and invertase in the bioprocess medium was influenced by inulin concentration and microelement composition. The main parameters for bioprocesses were: inoculum size 2% (v/v), pH 6, temperature 280 C and 220 rpm agitation speed. Following comparative study for production of extracellular inulinase (exo and endo inulinase) and invertase were obtained for Candida arborea the best results, invertase production having significantly higher concentrations than inulinase (35.92 U/mL invertase activity vs. 8.01 U/mL inulinase activity), on M5 medium. These results could be useful for industrial applications such as food industry, pharmaceutical.
Inulinases are enzymes catalysing hydrolysis of polyfructosans to produce fructose or fructooligosaccharides; these properties have attracted interest of many researchers towards exploring various plant sources (agro food waste) as substrates. According to the literature, various microorganisms, such as fungi, yeast, bacteria, and actinomycetes, can synthesize inulinase. Producer microorganisms can be the micromycetes Aspergillus, Penicillium, Rhizopus and Fusarium, the yeast Kluyveromyces and the bacteria Clostridium thermosuccinogenes and Bacillus subtilis, using inulin, sucrose, fructose, lactose, raffinose, xylose as sources of carbon. The present study mainly envisages inulinase produced by Aspergillius species grown on a fermentation medium based on different carbon sources (inulin and agro-alimentary by-products). The crude extract was purified by fractional precipitation with ammonium sulphate. The dissolved and dialyzed precipitate was further purified by ion exchange chromatography on DEAE-Sephadex. The experiments led to the obtaining of an inulinase with a specific activity of 43.34 U/mg proteins. Inulinase immobilization tests on chitosan beads have led to a stable biocatalyst at temperature and pH variations that could be useful for obtaining fructose syrup.
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