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PROPANEDIOL 2
1.3-Propanediol - A versatile bulk chemical from renewable resources by novel biocatalysts and process strategies

Recent developments in the use of 1.3-propaneidol (PD) as a monomer for novel polyesters and biodegradable plastics has led to a strong market need for the economical and sustainable production of this emerging bulk chemical, preferably via a biological route. PD can only be produced naturally by micro-organisms from glycerol. The present production volume and price of glycerol makes the biological route more expensive than the chemical route. This proposal is to extend the substrate spectrum of microbial PD to cheaper and more abundant renewable resources (glucose, starch and sucrose, by designing new biological pathways and biocatalysts with genetic tools and by developing novel process configurations. The process will be demonstrated on a pilot plant scale. It will open new ways for the flexible utilisation of renewable resources for non-food, value-added products.

Objectives
1) to develop new biological pathways and biocatalysts with molecular-biological tools and novel bioprocess control strategies for the economical production of a versatile bulk chemical, 1.3-propanediol
2) to provide a flexible and sustainable way of using cheap and abundant renewable resources (such as glucose, starch and sucrose) to produce value-added, non-food products.
The economical and technical feasibility of the processes developed will be analysed and the most favourable one will be demonstrated on a semi-industrial scale.

Progress to Date
1) Several improved recombinant strains (E. coli, S. cerevisiae, C. butyricum and K. pneumoniae) were developed for the conversion of glucose to glycerol and 1.3-propanediol in one-step or two-step processes respectively.
2) Fed-batch and continuous fermentation processes were improved with high yield (close to theoretical maximum in different pathways) and final product concentration (for glycerol conversion to 1.3-propanediol).
3) An economical evaluation for the production of 1.3-propanediol from glycerol and glucose with different strains was carried out. Based on this evaluation, a pilot plant trial was carried out on the most favourable process.

Results
For glycerol overproduction by yeast, four recombinant S. cerevisiae strains were constructed and studied. Glycerol production by strain HC13 was 4-15 times higher than that obtained from the other three strains, leading to a maximum glucose conversion to glycerol of 0.48 mol/mol in anaerobic batch cultures.
The successful expression of a synthetic operon containing the GPD1 and GPP2 genes from S. cerevisiae for glycerol production in E. coli was reported previously. Further study with the recombinant E. coli revealed the evolution of a mutated glycerol pathway. A fusion protein that catalyses the GPD1 and GPP2 activities is the content of a new patent application.
The genetically engineered C. acetobutyricum for converting glucose to glycerol was further improved. The performance of the strains in fermentation was, however, not satisfactory and is being improved.
Recombinant strains of K. pneumoniae with over-expression of the genes dhaB and dhaT have been investigated under real fermentation conditions. Surprisingly, the enhanced activities of glycerol dehydratase and 1.3-PD oxidoreductase did not lead to improved formation of 1.3-PD.
New medium and fed-batch strategies have been developed that significantly shortened the fermentation time and increased production, and was successfully applied to the glycerol fermentation by C. butyricum.

Classified in NON-FOOD PRODUCTS

Scientist responsible for the project

Dr AN-PING ZENG
Mascheroder Weg, 1
38124 Braunschweig
Germany - DE

Phone: +49 531 6181188
Fax: +49 531 6181751
E-mail: AZE@GBF.de

References

Project ID QLRT-1999-01364
Organisation GBF Gesellschaft für Biotechnologische Forschung mbH
Area 5.2
Start date 01 February 2000
Duration (months) 48
Total cost 1 563 400 €
Total EC contribution   1 171 169 €
Status Completed

The partners

  • Universidade Católica Portuguesa - Escola Superior de Biotecnologia, Portugal - PT
    ivasc@esb.ucp.pt
  • GBF-Gesellschaft für Biotechnoloische Forschung GmbH, Germany - DE
    AZE@GBF.de
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