Topic outline

  • General

    Hello everyone! My name is Paulina Marciniak, I am doctoral student, I am dealing with biopolymers so i want to give you some information about it. Some extra information can you find in articles which titles you find in this course.This course is dedicated to students from the faculty of Biology and Biotechnology (Master degree study). If you have questions please contact me 

    Paulina Marciniak, email: paulina.marciniak@uwm.edu.pl 

    This course relates the production and the usage of bioplastics in the world. The course addresses issues such as the using of microorganisms for the production of biopolymers, especially polyhydroxyalkanoates. This course teaches the principles of bacterial culture in the direction of PHA synthesis, breeding methods, types of culture and extraction of polymers. The gas chromatography method necessary for monomeric determination of obtained PHA is also mentioned. During this course the student learns logical thinking, breeding with the use of living organisms forces the anticipation of various situations and repairing the errors quickly. The knowledge presented in this course forces to think about protecting the environment and the future of our planet.


    The number of lessons: 3


    The goals of teaching:
    • First lesson: learning the basic knowledge about biopolymers - their types, methods of their production and their applying in human life
    • Second lesson: presentation of basic knowledge about one of the biopolymers groups -polyhydroxyalkanoates (PHAs) (presentation of their structure, division, features and applications). To familiarize students with the methods of cultivating of microorganisms towards the synthesis of PHAs (types of culture, required conditions) and microorganisms applied for this purpose
    • Third lesson: presentation of the classic and latest methods of PHAs’ extraction from microorganisms (solvent extraction, enzymatic digestion, mechanical disruption, Gamma irradiation). Presentation of gas chromatography analysis performed in order to know the monomer composition of the obtained polymers


    Student after this course:
    • can give a definition of biopolymers, their division and application
    • knows the definition of polyhydroxyalkanoates, knows the basic structure of PHAs, knows what they are used for
    • is able to present the most common PHAs producers, list the types of cultivation methods and required conditions during cultivation
    • can tell about extract and purify of PHAs from microorganisms
    • is able to list the principles of performing gas chromatography analysis (how it works etc.)
    • can say why it is so important to replace synthetic plastics by biodegradable biopolymers.

  • First lesson - biopolymers

    Biopolymers are polymers produced by living organisms. They are polymeric biomolecules. Biopolymers contain monomeric units that are covalently bonded to form larger structures. There are three main classes of biopolymers, classified according to the monomeric units used and the structure of the biopolymer formed: 

    • polynucleotides (RNA and DNA), which are long polymers composed of 13 or more nucleotide monomers
    • polypeptides, which are short polymers of amino acids
    •  polysaccharides, which are often linear bonded polymeric carbohydrate structures. 
    • Other examples of biopolymers include rubbersuberinmelanin and lignin.

    A major defining difference between biopolymers and synthetic polymers can be found in their structures. All polymers are made of repetitive units called monomers. Biopolymers often have a well-defined structure, though this is not a defining characteristic (example: lignocellulose): The exact chemical composition and the sequence in which these units are arranged is called the primary structure, in the case of proteins. Many biopolymers spontaneously fold into characteristic compact shapes (see also "protein folding" as well as secondary structure and tertiary structure), which determine their biological functions and depend in a complicated way on their primary structures. Structural biology is the study of the structural properties of the biopolymers. In contrast, most synthetic polymers' have much simpler and more random (or stochastic) structures. This fact leads to a molecular mass distribution that is missing in biopolymers. In fact, as their synthesis is controlled by a template-directed process in most in vivo systems, all biopolymers of a type (say one specific protein) are all alike: they all contain the similar sequences and numbers of monomers and thus all have the same mass. This phenomenon is called monodispersity in contrast to the polydispersity encountered in synthetic polymers. As a result, biopolymers have a polydispersity index of 1.

    Examples of biopolymers:

    • cellulose is a carbohydrate and 40 percent of all organic matter is cellulose.
    • starch is found in corn, potatoes, wheat, cassava, and some other plants. Annual world production of starch is over 70 billion pounds, with much of it being used for paper, cardboard, textile sizing, and adhesives.
    • collagen is a protein found in mammals. Gelatin is denatured collagen, and is used in sausage casings, capsules for drugs and vitamin preparations, and other miscellaneous industrial applications.
    • casein, commercially produced mainly from cow’s skimmed milk, is used in adhesives, binders, protective coatings, and other products.
    • soy protein and zein are plant proteins which are used for making adhesives and coatings for paper and cardboard.
    • polyesters are produced by bacteria, and can be made  on large scales through fermentation.They are now being used in biomedical applications.

    Main features:

    • abundant
    • renewable
    • biodegradable. 

    The usage:

    • Starch-based bioplastics can be processed by all of the methods used for synthetic polymers, like film extrusion and injection moulding. Eating utensils, plates, cups and other products have been made with starch-based plastics.
    • Soybeans can be processed with modern extrusion and injection moulding methods.
    • Water soluble biopolymers are used for flexible films mainly as food coatings. They have potential use as non supported stand-alone sheeting for food packaging.
    • Polyesters are now produced from natural resources-like starch and sugars-through large-scale fermentation processes, and used to manufacture water-resistant bottles, eating utensils, and other products.
    • Poly(lactic acid) has become a significant commercial polymer. Its clarity makes it useful for recyclable and biodegradable packaging, such as bottles, yogurt cups, and candy wrappers. It has also been used for food service ware, lawn and food waste bags, coatings for paper and cardboard, and fibers-for clothing, carpets, sheets and towels, and wall coverings. In biomedical applications, it is used for sutures, prosthetic materials, and materials for drug delivery.
    • Triglycerides have recently become the basis for a new family of sturdy composites. With glass fiber reinforcement they can be made into long-lasting durable materials with applications in the manufacture of agricultural equipment, the automotive industry, construction, and other areas. Fibers other than glass can also be used in the process, like fibers from jute, hemp, flax, wood, and even straw or hay. If straw could replace wood in composites now used in the construction industry, it would provide a new use for an abundant, rapidly renewable agricultural commodity and at the same time conserve less rapidly renewable wood fiber.

  • Second lesson - polyhydroxyalkanoates

    Among the various groups of biopolymers are polyhydroxyalkanoates. Microbial biopolymers called polyhydroxyalkanoates are synthesized intracellularly under imbalanced growth conditions, is is, for example, limitation of nitrogen or phosphorus with simultaneous excess of carbon source in the environment. These structures are synthesized in the form of granules which constitute a reserve material for the bacterial cells.

    Polyhydroxyalkanoates are linear polyesters consisting of hydroxy acid monomers connected together by an ester bond. Depending upon the number of carbon atoms in the monomers, PHAs are classified into three groups. The first is short-chain length PHAs, like poly(3-hydroxybutyrate) containing from 4 to 5 carbon atoms in a monomer, next is medium-chain length PHAs with 6-14 carbon atoms in each monomer. The xample is poly(3-hydroxyhexanoate)  and the last, long-chain length PHAs (PHALCL) like poly(3-hydroxyhexadecanoate) which contain more than 14 carbon atoms. These three groups differ in properties. PHASCL are highly crystalline and stiff. They are characterized also by strong brittleness with poor elastic properties. PHAMCL  have a low degree of crystallinity with a low melting temperature. Moreover, possess low tensile strength and high elongation to break.

    Bacterial polyhydroxyalkanoates are characterized by hydrophobic, are non-toxic, insoluble in water and also are biocompatible. Such features enable their broad range of applications in e.g. medical fields,tissue engineering, food and packaging industry,  pharmaceuticals and production of other useful products. Polyhydroxyalkanoates are biodegradable already within one year in the aquatic and terrestrial environment by external enzymes excreted by the environmental microorganisms. For this reason, it would seem that replacing petroleum polymers by PHAs could greatly improve the state of the environment and resolve problems related to waste disposal and storage. However, the production of biopolymers on a larger, industrial-scale is still limited due to high production costs. For several years, it is paid more attention to the use of cheap, waste substrates for PHAs production what can reduce the costs of this process.

    In PHA production we can use thermophilic and mesophilic bacteria, which are often found in an environment like Escherichia coli, Pseudomonas sp., Bacillus subtilis, Staphylococcus sp., Halomonas sp., Paracoccus sp., 

    Cultivation methods apllied in PHAs synthesis: 

    • batch
    • fed-batch
    • continuous fermentation
    • solid-state fermentation strategy.

    In these methods some specific conditions must be required:

    • the appropriate temperature of cultivation (for mesophilic bacteria is about 20-28 degree Celsius, for thermophilic bacteria is 28-35 degree Celsius)
    • available oxygen
    • appropriate pH (e.g for Halomonas sp. 9, for Paraccocus sp. 7)
    • nitrogen to carbon ratio
    • available micro and macroelements.
  • Third lesson - Extraction and analysis of PHAs

    After cultivation, the last point is extraction and purification of obtained biopolymers. Usually, PHAs are sourced from dry biomass formed by double centrifugation. Cells are usually lyophilized earlier. Subsequently, biomass is shaken in chloroform in order to degrade cells and release the PHA granules contained in them. Generally, chemicals which destroy membranes and release of granules are often used. The widely strategy is using a solvent, for example, chloroform, acetone, dichloroethane or propylene carbonate.  But enzymatic techniques are also possible to microbial separation. Then PHAs are filtered through a Whatman paper filter to remove bacterial cells and dissolved in chloroform. Then, obtained biopolymers are precipitated with cold methanol or ethanol. After evaporation of alcohol is possible to collect of PHAs, analysis of composition and various properties.  To determine of their monomer composition is common to use such methods like gas chromatography, mass spectroscopy or also nuclear magnetic resonance. For determining molecular weight, light scattering, chromatography, analysis of sedimentation process and measurement of intrinsic viscosity are used. Melting point, glass transition temperature or mechanical properties can be identified thought various available methods like Differential Scanning Calorimetry or Thermogravimetric Analysis.