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technology of PHA |
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Recommedation Tech |
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Manufacturing technology of PHA |
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Manufacturing
technology of PHA |
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Tsinghua
University and the Institute of Microbiology
under the Chinese Academy of Sciences have
incorporation fulfilled the breakthrough tasks
of biodegradable plastics, which includes
four sub-subjects: production of polyhydroxybutyrate
(PHB) using waste molasses as substrate; production
of PHB by recombinant microorganism; production
of PHB and its copolymer PHBV using hydrolyzed
starch as substrate; PHB property modification
and its application research. Besides, the
third generation of PHA namely PHBHHx has
been produced in a certain scale for the first
time in the world providing broad prospects
for the research on biodegradable plastics
commercialization in China.
Production of PHA using waste molasses as
substrate
In this sub-subject,
the major task is pilot-scale study on PHA
(The typical representatives is polyhydroxybutyrate
PHB) manufactured by fermentation using waste
molasses as substrate which helps to design
proper process route and provides a basis
for industrial production. The technical and
economic indexes were: 70g/L cell dry weight,
70% PHB yield, millions molecular weight,
more than 95% product purity and less than
50 yuan/Kg the production cost of PHA. The
researcher of Tsinghua University resolved
the following key technical points by doing
a great deal of work:
(1) reduced the
cost of fermentation raw material by using
waste molasses as substrate.
(2) Azotobater
Vinelandii UWD was used as the producing strains
in the fermentation production, which not
only can synthesize high molecular weight
PHB, but also can utilize waste molasses.
(3) solved the
problem of supplying oxygen under high density
culture.
(4) simplified
the process of breaking cell and releasing
intracellular PHB particles.
Finally, the cost
of PHB was successfully reduced to 40 yuan/Kg.
Production of PHA by recombinant microorganism
In this sub-subject,
the main task were constructing gene engineering
recombinant strains to carry out the laboratory
research on PHB fermentation production and
establishing a new process using cheap carbon
source(starch hydrolysate) to ferment, which
helps to provides a basis for pilot-scale
and industrial production. The assessment
target and technical&economic indexes
were: 200g/L cell dry weight, 70% PHB yield,
more than 95% product purity, less than 50
yuan/Kg the production cost of PHA.
The following key
technical points were solved:
(1) constructed
multifunctional new strain of gene engineering
which can efficiently express and produce
PHB and synthesize biodegradable plastics
utilizing cheap carbon source (starch hydrolysate)
to reduce the cost of fermentation raw material;
solved the problem of supplying oxygen under
high density fermentation; developed the process
simplifying breaking cell and releasing intracellular
PHB particles; adopted a new purifying process
not using organic solvent extraction.
(2) did research
on optimization controlling condition of fermentation
technology and fermentation process using
multifunctional strain so as to implementation
requirements of fermentation in the tackling
technical indexes.
(3) researched
the process of cell post-treatment and PHB
purification whose cost was as low as possible.
The optimal strain
VGI (pTU14) was chose from more than 40 constructed
strains. The experiment results indicated
that the content of PHB accumulated in the
strain cells reached to more than 90%. More
than 90% cells had decomposed when the fermentation
finished because this strain had cell decomposition
gene. When VGI was adopted, the strain content
(dry weight) in the fermentation liquid was
215.9 g/L, PHB accounted for 89.7% of the
strain dry weight, the product purity was
over 98% and the cost of PHB was 45 yuan/Kg.
Production of PHA using hydrolyzed starch
as substrate
In this sub-subject,
the main task were carrying out pilot-scale
study on PHA production by fermentation based
on experiments and establishing a new process
using cheap carbon source(starch hydrolysate)
to ferment but not using organic solvent extraction
to purify. The task demanded more than 130g/L
strain content in the fermentation liquid,
1.5g(PHA)/(L•h) production intensity and less
than 50 yuan/Kg production cost.
In the 1.2t fermentor,
high density culture of cells was realized
by effectively controlling the equilibrium
growth condition of cell growth and non equilibrium
growth condition of PHA accumulation. In the
five batches experiments, the average fermentation
time was 58h, the average cell content was
134.3 g/L(dry weight) and the maximum reached
to 164.4 g/L(dry weight), PHA accounted for
78% of the strain dry weight and the maximum
reached to 80%, the average production intensity
was 1.84g(PHA)/(L•h) and the maximum reached
to 2.18g(PHA)/(L•h), the average conversion
rate of glucose to PHA was 0.28 the maximum
reached to 0.30.
Moreover, not only
the extraction process was simplified and
the extraction efficiency was improved but
also the production was reduced through collecting
PHA particles by centrifuge after cell decomposition.
The average extraction rate of PHA was 84.3,
purity was over 95% and the cost of PHA pilot
scale production was 35-43 yuan/Kg.
PHB property modification and its application
research
In order to be
plastic product, PHA manufactured by microbial
fermentation must be modified. The main task
of this sub-subject were producing fine performance
degradable polymer materials by combining
various additives(such as plasticizer, foamer
fluidity modifier, etc.) with other polymer
materials and investigated their application
in the field of thin film, vessel, medicine,
agriculture so that their application performance
were determined furtherly. Meanwhile, the
research on reducing cost was done.
The assessment
target and technical&economic indexes
were: doing some research on PHA process technology
in order to obtain fine performance(process
and physical properties) degradable polymer
materials; developing and researching on the
application of various PHA products. The following
work was done:
(1) modification
of PHB
Researched PHB
crystallization behavior under different conditions,
especially investigated PHB crystallization
process and the influence of one-component
and two-component nucleating agents(containing
NH4Cl,BN, CaCO3 and various aliphatic dibasic
acids) on PHB crystallization; studied blending
modification of PHB; studied the synergetic
effect between plasticizer epoxy soybean oil
and nucleating agents TMB-3, TMB-4, TMB-5
and Tween 80. Finally, the extrusion and injection
process of modified PHB were implemented successfully
and the samples were obtained.
(2) application
of PHB
Made micro balls
and micro rods by using PHB、bovine serum albumin(BSA)
and medicines such as D-18 methyl levorotation
norethisterone(LNG) and studied their drug
release rate furtherly; researched the preparation
process and the biocompatibility、in vitro
degradation and surface modification of PHB
stents; carried out Osteoblast implantation
and culture experiments on PHB three-dimensional
porous stents corporating with Academy of
Military Medical Sciences; researched surface
coating of PHB on biodegradable dishware(rice
bowl), in which not percolated dishware in
boiling-solution was made by brush coating
on the dishware pressed from farm land straw.
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