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Biopolyester production from carbon sources and their potential utilisation in food preservation.

Biopolyester formation will be achieved by feeding micro-
organisms on edible oily acids, carbohydrates and some
aliphatic carboxylic acids to produce polyhydroxy-
alkanoates. Potential food application will be examined.

Demands on ready to eat foods, and on minimally processed fruits/vegetables, are increasing because of the busy lifestyles, increased purchasing power and health-conscious trends of consumers. This desire for fresh or freshlike properties has led to an increase in popularity of fresh fruits and vegetables that has extended to other types of product coupled with the search for convenience and extension of shelf life. Different storage techniques have been developed for fresh horticultural commodities in order to extend their marketing distances and holding after harvest. According to some reports, it has been estimated that 25% to 80% of the world's harvested fruits and vegetables is lost to spoilage. Biodegradable films and coatings made from biopolymers have received increasing interest over recent decades for the preservation of foods. Biodegradable polyesters are polymers which completely degrade in soil and water within a couple of weeks via microbial attack. Bacteria, such as pseudomonas and alcaligenes, belonging to genera to be used in this project accumulate polyesters or poly hydroxyalkanoic acids (PHAs) as intracellular storage materials of energy when an essential nutrient becomes depleted and polymer forming substrate is added. These bacteria species will be grown on different sources of carbon such as alcohols, carbohydrates, alkanoic acids and alkans, including edible oily acids. Depending on the substrates used in the growth medium, a variety of polyesters and subsequently biodegradable plastic materials can be obtained. Phases of the project will be as follows: 1. Development of micro-organisms in fermenters of different capacities (2/10L) on carbon sources in order to obtain biopolyesters 2. Yield improvement of biopolyester produced by changing the culture conditions 3. Selection of convenient drying, extraction, filtration, purification or separation methods 4. Characterisation of chemical structure of biopolyesters by nuclear magnetic resonance, spectroscopy, gel permeation chromatography and differential scanning calorimetry techniques 5. Production of biopolyester packaging goods and investigation of their properties; measurement of solvent resistance, tensile strength, gas permeabilities and UV resistance 6. Improvement of physico mechanical, thermal and optical properties of materials 7. Preparation of synthetic analogues of natural polymers and their blends with natural polymers 8. Selection of packaging materials with desired properties 9. Measurement of the biodegradability of materials produced. Production of microbial biodegradable polyesters relates with the European Parliament and Council Directive 94/62/EC on packaging and packaging waste. Packaging can enter into the market only if it fills all basic demands stated in the Directive and Appendix 2. The appendix states briefly, among other clauses, that packaging shall be designed in such a way as to minimise its impact on the environment when packaging waste or residues from packaging waste management operations are disposed of. A project conducted with financial support from the EU sets out a practical application of optimal mild preservations techniques. An important aspect of this project (AIR-1-0125) is the design and application of edible biodegradable coating and packaging materials which can be applied directly to the surface of a good product. Biopolymer films and coatings which are formed of polysaccarides composed of cellulose and derivatives, starch and derivatives and gums or protein based on gelatin, zein and gluten, have good mechanical and optical properties but are highly sensitive to moisture and show poor water vapour barrier properties. On the other hand films composed of polyhydroxyalkanoate have good water vapour barrier properties but are usually opaque and relatively inflexible. Therefore attempts will be made to decrease the brittleness of PHAs by incorporating comonomers or by blending with other natural polymers or chemically synthesised polymers. Depending on the monomers of the composition of substrate fed to bacteria, a wide variety of mechanical properties from hard cristalline to elastic can be obtained for the family of PHAs. Thus production of new biopolyester films with different properties is aimed for. The material properties can be controlled by adjusting the rate of comonomer fractions. Conventional equipment will be used in this project to process different PHA polymers and blends. Equipment to be tested can include bottle blow, injection moulding, film processing, thermoforming, extrusion coating and lamination. Keywords: micro-organisms, biopolyesters, biodegradable packs.
Acronym: 
MICROPOL
Project ID: 
2 004
Start date: 
01-09-1998
Project Duration: 
36months
Project costs: 
450 000.00€
Technological Area: 
Market Area: 

Raising the productivity and competitiveness of European businesses through technology. Boosting national economies on the international market, and strengthening the basis for sustainable prosperity and employment.