INDUSTRIAL MICROBIOLOGY for diploma 11 BIOPLASTICS Prof Dr
INDUSTRIAL MICROBIOLOGY (for diploma) (11) BIOPLASTICS Prof. Dr. Waiel Farghaly Prof. of Microbiology/ Dept. Botany, Fac. Science
►Bioplastics, sometimes also called green plastics, are plastics that are biodegradable and are made mostly or entirely from renewable resources. ►Like all plastics, bioplastics are composed of a polymer, combined with plasticizers and additives. What makes these plastics "green" is one or more of the following properties: 1. renewable ingredients 2. biodegradable 3. environmentally friendly processing 1. Because different compounds can satisfy some or all of these criteria to different degrees, there are different "degrees of green" in green plastics.
DEVELOPMENT ► John Wesley Hyatt Jr. , in 1869, looking for ivory substitute for billiard balls, patented a cellulose derivative for coating non- ivory billiard balls. That attempt, was affected by the coating's flammability and soon he developed celluloid now widely known for its use in photographic and movie film. ► World War II brought on a large increase in synthetic plastics production in the 1900’s. ► In the 1920 s Henry Ford experimented with using soybeans in the manufacture of automobiles. Soy plastics were used for an increasing number of automobile parts. ► In 1960, cellophane, a sheet material derived from cellulose was invented. It is still used in packaging candy, cigarettes, and other articles.
► In the 2000's and Beyond, demand for materials like plastics is continually growing. ► The pressures of increasing waste and diminishing resources have lead many to try to re- discover natural polymers and put them to use as materials for manufacture and industry. As a result, there is increasing interest in the promise of a new generation of green plastics. ► The main source of the chemicals needed to manufacture plastics are fossil fuels. These petrochemical plastics are very durable, but take a long time to biodegrade when disposed. ► Rising concern about the cost of fossil fuels, and their impact on the environment has resulted in a search for alternatives to petrochemical plastics, namely biopolymers and bioplastics.
BIOPOLYMERS AND BIOPLASTICS ► Biopolymers are polymers which are present in, or created by, living organisms. These include polymers from renewable resources that can be polymerized to create bioplastics. ► Bioplastics are plastics manufactured using biopolymers, and are biodegradable.
Types of biopolymers ► There are two main types of biopolymers: those that come from living organisms; and, those which need to be polymerized but come from renewable resources. Both types are used in the production of bioplastics.
BIOPOLYMERS FROM LIVING ORGANISMS Different biopolymers; their nature and sources Biopolymer Natural Source Composition Cellulose Wood, cotton, corn, wheat, and others This polymer is made up of glucose. It is the main component of plant cell walls. Soy protein Soybeans Protein which naturally occurs in the soy plant Starch Corn, potatoes, wheat, This polymer is one way carbohydrates tapioca, and others are stored in plant tissue. It is a polymer made up of glucose. It is not found in animal tissues. Polyesters Bacteria These polyesters are created through naturally occurring chemical reactions that are carried out by certain types of bacteria.
Polymerizable Molecules ► These molecules come from renewable natural resources, and can be polymerized to be used in the manufacture of biodegradable plastics. ► There are two methods to produce plastics. The first uses fermentation, and the second relies on the plant to become the factory for plastic production. Biopolymer Lactic Acid Natural Source Composition Beets, corn, potatoes, and others Produced through fermentation of sugar feed stocks, such as beets, and by converting starch in corn, potatoes, or other starch sources. It is polymerized to produce polylactic acid - a polymer that is used to produce plastic. Triglycerides Vegetable oils These form a large part of the storage lipids found in plant and animal cells. Vegetable oils are one possible source of triglycerides that can be polymerized into plastics.
USING FERMENTATION TO PRODUCE PLASTICS ► There are two ways fermentation can be used to create biopolymers and bioplastics. 1 - Bacterial Polyester Fermentation: ► A bacterium called Ralstonia eutropha is used to ferment the sugar of harvested plants, such as corn, to fuel their cellular processes. The byproduct of these cellular processes is the polymer. The polymers are then separated from the bacterial cells.
2 - Lactic Acid Fermentation: ► Lactic acid is fermented from sugar, then it is converted to polylactic acid using traditional polymerization processes.
GROWING PLASTICS IN PLANTS ► Researchers created an Arabidopis thaliana plant through genetic engineering. The plant contains the enzymes used by bacteria to create plastics. The researchers have transferred the gene that codes for this enzyme into the plant, as a result the plant produces plastic through its cellular processes. ► The plant is harvested and the plastic is extracted from it using a solvent. The liquid resulting from this process is distilled to separate the solvent from the plastic.
BIOMATERIALS ► The term ‘biomaterials’ includes chemically unrelated products that are synthesised by microorganisms (or part of them) under different environmental conditions. ► One important family of biomaterials is bioplastics. These are polyesters that are widely distributed in nature with physicochemical properties resembling petrochemical plastics. ► These polymers (usually lipid in nature) are accumulated as storage materials (in the form of mobile, amorphous, liquid granules), allowing microbial survival under stress conditions. ► The number and size of the granules, the monomer composition, macromolecular structure and physico-chemical properties vary, depending on the producer organism. They are intracellular light- refracting granules that, in overproducing mutants, cause a striking alteration of the bacterial shape
Scanning (a, b) and transmission (c, d) electron microphotographs of P. putida (a, c) and its β-oxidation mutant (b, d) cultured in a chemically defined solid medium containing 7 -phenylheptanoic acid (5 m. M) as a source of aromatic PHAs and 4 -hydroxyphenylacetic acid (5 m. M) as an energy source. Bar = 1 μm.
► Microbes belonging to more than 90 genera — including aerobes, anaerobes, photosynthetic bacteria, archaebacteria and lower eukaryotes— are able to accumulate and catabolize these polyesters. ► Examples are Chromatium vinosum, Thiocystis violacea, Thiocapsa pfennigii and Synechocystis sp. PCC 6803 ► The most widely produced microbial bioplastics are PHB, PHA and their derivatives. ► Other polyesters can also be produced by microorganisms.
INDUSTRIAL PRODUCTION There are three important limitations in the bulk production of bioplastics: 1 - the special growth conditions required for the synthesis of these compounds (usually unbalanced nutrient conditions that cause slow growth) 2 - the difficulty involved in the synthesis from inexpensive precursors 3 - the high cost of their recovery. ► ► Construction of recombinant organisms (other microbes, yeasts and plants) enabled the synthesis of bioplastics from inexpensive carbon sources (e. g. molasses, sucrose, lactose, oils and methane). ► Currently, traditional fermentations carried out with recombinant bacteria and transgenic plants cannot compete with the conventional industrial production of synthetic plastics.
BIOTECHNOLOGICAL APPLICATIONS ► Many different applications have been described for bioplastics since the first industrial production of Biopol 1 by ICI Ltd in 1982. ► Initially, they were used for the fabrication of bottles, fibres, latex and several products of agricultural, commercial or packaging interest. ► Currently, these polyesters have been employed for medical applications such as neural- and cardiovascular-tissue engineering, fracture fixation, treatment of alcohol addiction, cell microencapsulation, support of hypophyseal cells, or as precursors of anti- rheumatics, analgesics, etc.
BIOPLASTICS AND THE ENVIRONMENT ► For bioplastics to become practical, they must have properties that allow them to compete with the current plastics on the market: bioplastics must be able to be strong, resiliant, flexible, elastic, and above all, durable. ► Current research on bioplastics is focusing on how to use nature's polymers to make plastics that are programmeddegradable. There at least three factors that affect how environmentfriendly a material is: ► renewability: how quickly are the ingredients that go into making the plastic created in the environment? ► degradability: how quickly can the plastic be re- integrated into the environment after it is no longer being used? ► production: how much pollution or waste is created during the process of actually making the plastic? ► ► Traditional plastics fail on all three of these points.
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