Biolac

Other bioplastic which is easily biodegradable are polylactides (PLA) and pol yglycolides (PGA). The earlier efforts in this field are by American Cyanamid Corporation which developed the first synthetic absorbable suture material. The product, Dexon was a polyglycolic acid homopolymer. Vicryl was developed then by Dupont which has 92:8 glycolic acid : lactic acid as copolymer. PLA and PGA are thermoplastics and are biodegradable polyesters. Low Mr polylactic acid and polyglycolic acid are made by direct polymerization of respective acids. The high Mr, PLA and PGA are made by ring opening polymerization of lactide and glycolide which are cyclic diesters of respective acids. Polyglycolic acid and polylactic aid have degradation time in few days and few weeks respectively while polylactides and polyglycolides have degradation time in few months to years. 

Researchers at the University of Wisconsin, USA, have produced biodegradable and photodegradable polymers from l-lactic acid. The researchers are working on a project to produce l-lactic acid from whey permeate. The technology to fer ment whey to lactic acid is in fact quite old but the end product is mixture of l-lactic acid and d-lactic acid. The pure l-lactic acid is worth nearly 3 times as much the mixture of l- and d- lactic acids. Pure l-lactic acid has several uses. It can be u sed to manufacture polylactides (plastics made from lactic acid that are bio- and photodegradable), as food preservative, as flavour enhancer and as acidulant and in pharmaceutical industry (in IV solution and drug delivery).

The Ecological Chemical Products Co. (ECOCHEM) has recently opened a $ 20 million commercial plant in Adel, Wisconsin to produce high-pure natural lactic acid and polylactide polymers for food and pharmaceutical applications. ECOCHEM is a joint venture of DUPONT and Con. Agra. Inc. ECOCHEM's manufacturing process has environmental advantages such as raw materials derived from natural byproducts of cheese industry, no new wastes generated during its production and recycled side streams producing either useful or environmentally acceptab le co-products. 

Production of lactic acid-based plastics from starchy food wastes and by-products is also on the way of commercialization. The Argonne National Laboratory has licensed key steps in its Biolac process to Kyowa Hakko USA Inc., a US subsidiary of Japan's Kyowa Hakko, which deals in fermentation products. Kyowa Hakko plans to carry out further research and development aimed to commercialization. PLA and PGA are having mainly medical applications, as sutures, as ligament replacements, for resorbable plates and screws in fracture fixation (i.e. in orthopedic repairs), for controlled drug release, for arterial grafts. The Biolac plastic has commercial applications for compost bags, coatings for paper, seeds, pesticides, fertilizers and agricultural mulch films for timed release of pesticides and fertilizers. In t wo key steps that have been licensed, one converts glucose of starchy wastes to lactic acid and the other converts lactic acid to polylactic acid.

Potential market for PLA plastics and coatings as forcasted by Argonne National Laboratory, Illinois : -

• Controlled fertilizer and pesticide application - > 500 000 tonnes
• marine plastic applications - 250 000 tonnes
• degradable conditioner coatings for paperback stock - > 100 000 tonnes
• compost waste bags, sacs etc. - tens of thousands of tonnes
• agricultural mulch film - 75 000 tonnes

Polylactic acid can be produced in US since the US produces 5 million tonnes of food wastes in the manufacture of fried potatoes and 1-2 million tonnes wastes in the cheese industry. Kyowa Hakko USA Inc. want s to use this fact for producing polylactic acid by the Biolac process.

The 5000 tonnes / year capacity plant at a cost of $ 8 million will be operational at Port Cargill on Minnesota river near Minneapolis. It will make polylactic acid from lactic acid which is obtained by bacterial fermentation of sugars from corn, potato, milk, sugarbeet.

Cargill Dow Polymer (CDP) plans to produce 1,40,000 tonnes per year of commercial polymer from end of 2001 A. D. First plant will come up at Blair (Nebrasca, USA). Second plant will come up in Europe while the third is going to serve Asian markets. CDP is applying its Nature Works Technology to the processing of corn sugars to produce proprietary polylactide polymer (PLA) which is fully biodegradable. Corn starch is first converted to dextrose which is fermented to lactic acid. Lactic acid is then converted by condensation to lactide, a cyclic dimer. This lactide is purified through vacuum distillation. Ring opening polymerization of the lactide is accomplished with solvent free melt process. A wide range of products that vary in molecular weight a nd crystallinity can be produced. This enables wide range of applications. Wheat, maize, sugar beet and agricultural wastes are also being tried. CDP is working with several packaging and fibre manufacturers for development of applications. Clothing fibres, films, food containers and furnishings are amongst the many possible applications.

Archer Daniels Midland Co. and Warner Lambert Co. are among the companies gearing up to produce lactic acid from corn or starch that could be used in next generation biopolymer plastic.

Two Japanese companies Kobe steel Limited (Kobe) and Shimadzu Corp. (Kyoto) have perfected a low-cost continuous process for manufacture of biodegradable polymer - poly-2-lactic acid (PLLA). It can be produced at tens of thousands of capa city. PLLA melts at 170-180⁰Cand has vicat softening point of 58⁰C, a tensile strength of 700kg/cm and a transparency of 94%. It can be processed into a film of 10 to 500 Mm thickness and can be injection moulded. It can be produced at $2.54 to $4.23 per k g. It can be used for food containers, soil retention sheetings and agriculture film.

The physical properties of polylactic acid are similar to polystyrene. It can also be modified to make it similar to PE (Polyethylene) or PP (Polypropylene). It has performance benefits similar to petrochemical-based plastics but is biodegradable by composting. Applications of polylactic acid as plastic can be - disposable fast food, dairy and delivery containers, food service ware, medical garments, waste bags.

Asahi Che micals and Institute of Physical and Chemical Research in Japan have jointly discovered a new species of bacteria which synthesizes biopolyesters. The bacteria accumulate large quantities of polymers. The bacteria can use wide variety of compounds with 2- 22 carbon atoms as a source of carbon. In experiments, inexpensive oils and fats were used as carbon sources which produced polyester at a maximum yield of 45%. The yield will be increased to 60-70% when recovery process is optimized. High efficiency plast ic with low production cost is the aim of research work. The use of wide range (2-22 carbon atoms) compounds is advantageous. Product type and yield differ with type of feed used. The compound with 18 carbon atoms produces the highest recovery yields.

Biodegradable enviroplastic is developed by Planet Technologies, USA. It will be used for cosmetic, medical disposables, food service, personal hygiene product industries. It will dissolve in sludge compost or water without leaving any environmentally harmful residues.

Researchers at University of Iowa are investigating the synthesis of biodegradable plastic using enzymes in organic solvents. Sucrose and adipic acid are the substrates used and action of lipases and proteases is sought for to link sugar and d iacid into copolymer chain.

Polyglutamic acid (PGLU) is a water soluble polymer produced by Bacillus species. Bacillus subtilis releases polyglutamate in growth medium. Fermentations to produce PGLU have been patented some years ago but commercial product ion is not reported. Yields to the tune of 40 g/l of PGLU in 5 days are reported.

Japanese researchers at National Food Research Institute have developed wate r-resistant, biodegradable plastic films from corn protein. This newly developed plastic is expected to have wider applications such as food trays, because of low material cost and fabricability. The process is based on a protein called Thujene. It remain s in corn after removal of starch. Thujene is spread into thin transparent film after being dissolved in acetone. When it has thickness of around 70 �m the film is as strong as commercial wrapping film with respect to boring. The film rarely permeates water. It will be enzymatically decomposed in one month in ordinary soil.