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A Research team has discovered a
bacteria (Pseudonomas Putida) which could convert
styrene, an inherently toxic monomer of polystyrene
(PS), to produce polyhydroxyalkanoate (PHA),
a biodegradable plastic: the bacteria converts
the styrene into simple carbon units which are
then polymerized to form PHA. According to the
researchers, the biodegradable plastic thus
obtained can be used in a wide range of applications
including medical implants, scaffolds for tissue
engineering, heat resistant plastic, etc. The
team is improving the converting process before
its commercialization.
A medium chain length polyhydroxyalkanoate
(mclPHA, monomers from C6-C14) is a water insoluble,
biodegradable and biocompatible polymer that
it is well suited for medical applications.
For this purpose the polymer needs to be highly
pure, especially with respect to pyrogenic compounds.
Most commonly mclPHA is produced by certain
Gram-negative bacteria like Pseudomonas putida.
To obtain pure PHA, the intracellular PHA-inclusion
bodies must be separated from the other cell
components. The cells first have to be disrupted
and then the PHA-granules can be isolated. However,
cell components like nucleic acids, lipids,
proteins etc. can contaminate the PHA. Especially
lipopolysaccharides (LPS) from the outer cell
membrane are the main culprit for pyrogenic
contamination A very small amount of LPS causes
serious problems in pyrogenic contamination
Several recovery processes have been established
for short chain length PHA (sclPHA, C2-C5 monomer)
that has quite different physical properties
compared to mclPHA, whereas less attention has
been paid to the recovery of mclPHA.
In general recovery processes can be divided
into two categories: solvent extractions and
aqueous digestions. Both have to fulfill several
conditions: high purity of the end product,
avoidance of halogenated solvents, no degradation
of the polymer and high efficiency.
(Based on research conducted
by an Irish researchers team at the Dublin's
University College (UCD))
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