Prokaryotic PHA

In addition to prokaryotic PHA accumulation, low-molecular mass poly-hydroxybutyrate complexed to other macromolecular cell components like proteins or polyphosphates (cPHB) can be found in the tissue of eukaryotic organisms. cPHB classically occurs in low quantities in the organisms and does not serve as storage material not all of the details of its metabolic functions have been elucidated [9]. 

Poly(3-hydroxybutyrate) and a few other PHAs were in prokaryotic microorganisms and in eukaryotic micro-organisms as well as in higher organisms also found in complexes and/or associated with other molecules in the laboratory of Reusch [10]. In these cases PHAs do not occur as insoluble inclusions, have a much lower MW, and they contribute only marginally (about 0.2% of the cell dry... 

Polyhydroxyalkanoates (PHAs) are polyesters formed by many prokaryotic micro-organisms-when unbalanced nutritional conditions are chosen for die (Hoducing cells Up to more than 90% of the cell dry weight can be accounted for as polymer. Besides the homopolyester poly-R-3-hydroxybutanoate, consisting of 3-hydroxybutanoate (3HB) only, two main types of copolyesters can be formed by different microorganisms. The first type of PHAs always contains C3 units in the polymer backbone, but the... 

The biologically produced biopolyesters comprise a complex class of polyox-oesters [1-4] The majority of prokaryotes synthesize PHB and/or other PH As composed of medium-chain length (/ )-3-hydroxyfatty acids (6-14 carbon atoms) as reserve material. These polyesters are deposited as spherical water-insoluble inclusions in the cytoplasm (Figure 3.2). The biopolyester comprises the core of the granule. More than 150 different hydroxyalkanoic acids are known to occur as parts of PHAs implying that the respective CoA thioester are accepted as substrates by the PHA synthases (Figure 3.1). Some representative constituents are displayed in Figure 3.3. 

PHA operons expressed in prokaryotes or eukaryotes can be used to help enhance cellular robustness. This mechanism should be tested In more Industrial microbial strains aiming to select strains with better resistance to the stressed conditions and, as such, enhanced yields of the bio-products, including antibiotics, vitamins, and amino acids. 

Polyhydroxyalkanoates (PHAs) are naturally produced by microorganisms from various carbon substrates as a carbon or energy reserve. A wide variety of prokaryotic organisms (De Koning 1993 Madison and Huisman 1999) accumulate PH A from 30% to 80% of their cellular dry weight Biotechnological studies revealed that... 

In PHA modification, Mukai et reported that lipases originated from eukaryotes have broad specificities with the abilities to erode P(3HP), P(4HB), P(5HV) and P(6HH) films compared to prokaryote lipases, which could barely degrade all the polymers except P(3HP). This shows that lipases from prokaryotes have high substrate specificities for the hydrolysis of PHA. Jaeger et indicated that Pseudomonas alcaligenes. Pseudomonas fluor-... 

The PHB is one of the commercially available PHAs which find multiple applications in Food Industry. Polymer of 3-hydroxybutyrate, have been introduced into the market in relatively large quantities as bioplastic material. The PHB is accumulated as intracellular granules by many prokaryotic organisms (including /ca//gene5 spp.. Bacillus spp., Azotobacter spp., Pseudomonas spp.) as they enter the stationary phase of growth, to be used later as an internal reserve of carbon and energy... 

Hammes W, Weiss N, Holzapfel W (1991) The genera Lactobacillus and Camobacterium. In The prokaryotes, vol II, 2nd edn. Springer, Berlin, pp 1535-1594 Hardie JM (1986) Other Streptococci. In Sneath PHA, Mair NS, Sharpe ME, Holt JG (eds) Bergey s manual of systematic bacteriology, vol 2, 9th edn. William and Wilkins, Baltimore, MD, pp 1068-1071... 

Polyhydroxyalkanoates (PHAs) are homo- or heteropolyesters synthesized and intracellularly stored by numerous prokaryotes. They can be produced in large quantities from renewable resources by means of well known fermentation processes and the imposition of particular culture conditions, and a number of physical or chemical methods are known to extract them from the producing biomass. Production processes such as batch, semi-batch and continuous fermentation are all known to work. PHAs have properties similar to those of some polyolefins. This, combined with the fact that they are fully and rapidly biodegraded under the appropriate conditions, has generated a high interest in them as substitutes to petroleum-based polymers in many applications [1]. 

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