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Nature as chemical factory

The fact that petrol is becoming more and more expensive has a knock-on effect on the chemical industry. Biomass is an alternative carbon source. At Biotechnica 2008, which was held in Hanover, Germany, Fraunhofer researchers showed how chemical products can be produced from rape, whey and crab shells.

Petrol is the basis for many products in the chemical industry. However, this fossil material is becoming scarcer and more expensive. One alternative to petrol is renewable resources. However, the question arises as to whether it is necessary to produce bioethanol and other fuels from sugar cane or crop that are normally used for food. The answer is no. The use of white biotechnology enables the production of chemical substances from food industry waste products or from biomass remainder from forestry or agriculture. Researchers from the Fraunhofer Institute of Interfacial Engineering and Biotechnology IGB in Stuttgart will demonstrate how this can be done through the biotechnological exploitation of rape, whey and crab shells.

Plastics and varnish from rape

The production of biodiesel from rape oil produces raw glycerine as a by-product. IGB scientists have developed a method that allows the conversion of raw glycerine into 1,3-propandiol, a chemical raw material for the production of polyesters or wood varnish.

Up until now, 1,3-propandiol has been synthesised using chemical methods. However, there are also microorganisms that are able to convert glycerine into 1,3-propandiol. The bacterium Clostridium diolis produces a chemical substance in relatively high yields that can be used for the production of polyesters or wood varnish. However, Clostridium diolis cannot convert raw glycerine because the black substance, which resembles used engine oil, contains fatty acids which are left over from rape oil. These fatty acids have to be removed before further use. "In addition, higher glycerine and 1,3-propandiol levels inhibit the growth of the bacteria," said Dr. Wolfgang Krischke from the IGB pointing out further challenges associated with the development of a biotechnological process. "The continuous operation of the bioreactor solved this problem to a great extent. Glycerine is nearly 100 per cent converted and is thus unable to exhibit its inhibitory effect. This enabled us to achieve a stable process with high product concentrations."

Long-chain dicarbon acids are intermediary chemical products that can be generated from rape oil. These acids can be used for the production of polyamids and polyesters. Up until now, it has been difficult to chemically synthesise long-chain dicarbon acids. An alternative process is biotechnological production. "In rape oil, fatty acids are bound to glycerine. If the fatty acids are cleaved off, the free fatty acids can be converted into dicarbon acids by Candida yeasts," said Steffen Rupp from the IGB. Together with his IGB colleagues, Rupp has developed a fermentative process that involves genetically engineered yeasts and the simultaneous cleavage of rape oil and the conversion of fatty acids into dicarbon acids.

Bioplastics from whey

Whey is a waste product from the production of milk products. Up until now, whey has been disposed of in what is a very expensive disposal process. Lactic acid bacteria can be used to convert lactose (contained in whey) to lactate, which is not only used as a preservative and acidifier in food production, but can also be used as raw material in the chemical industry – for example in the production of biologically degradable plastics known as polylactides (PLA). Disposable dishes and surgical screws made from PLA are already on the market.

Fine chemicals from crab shells

Chitin is, after cellulose, the most frequent biopolymer on earth. The renewable materials accumulate in aquaculture and in the processing of seafood such as crabs. In the BioSysPro project, funded by the German Federal Ministry of Research and Education, IGB researchers are investigating whether it is possible to produce chitin with microbial chitinases for use as renewable material for the chemical industry. Many bacteria are able to degrade chitin with the enzyme chitinase, which cleaves the linear, insoluble homopolymer consisting of b-14,4 N-acetyl-glucosamine units into oligo- or monomers. The objective is to degrade chitin into monomers and use them in polymer chemistry. These monomers can be easily hydrothermally converted into modifiable constituents, for example nitrogen heterocycles.

“White biotechnology uses nature as a chemical factory. Traditional chemical production processes are replaced by microorganisms or enzymes,” said Prof. Thomas Hirth, director of the Fraunhofer Institute of Interfacial Engineering and Biotechnology IGB.

Source: Fraunhofer IGB - 29 Sept. 2008

Website address: https://www.biooekonomie-bw.de/en/articles/pm/nature-as-chemical-factory