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Valorisation of plant coarse meal through phosphate recovery and coupled poly phosphate synthesis

Phosphorus is an essential element for both plants and animals. The Federal Republic of Germany is entirely dependent on imports to cover its phosphorus demand. The production of phosphate ores however requires enormous amounts of water, fuels and resources. As the global amount of phosphorus deposits is diminishing, an increasing number of seams that are contaminated with uranium and cadmium are exploited, providing a gateway for these elements into our food chain.

  KnowVolution Copyright: © Royal Society of Chemistry The KnowVolution (knowledge gaining directed evolution) strategy

Hence, the target of the Value-PP project is the development of a novel integrated and sustainable technology concept for the biotechnological production of polyphosphate from plant grist as an alternative to their production from ore. This requires the mobilisation of phosphate from its phytate storage form, which can be achieved with phytase enzymes. The mobilised phosphate can in turn be accumulated by yeasts and transferred into polyphosphates. We aim to use an E.coli based phytase, as it can be easily and cost-effciently produced in E.coli or S. cerevisiae. Through Directed Evolution conducted in E.coli the project will increase the optimum temperature of the enzyme to 40°C to reduce energy costs due to heating/cooling in the process to a minimum.

As traditional protein engineering through Directed Evolution (e.g. error-prone PCR) comprises several iterative rounds of diversity generation and subsequent screening for improved enzyme variants, it often requires 12 to 24 months to generate significantly improved enzymes. Also, no deeper molecular insight into how these improvements were generated can be gained. Within the Value-PP project, we will apply two rounds of the considerably more effective KnowVolution strategy to tailor the E.coli phytase for the hydrolysis of phosphate in coarse meal/grist. In parallel, we will establish a biotechnological process for the production of the phytase that delivers sufficient amounts of phytase for large-scale grist treatment.

While the phosphate released via phytase is retained in yeasts, the remaining grist and coarse meal can still safely be used as animal feed after their treatment. The polyphosphate resulting from this process on the other hand can be applied in a multitude of technical applications.

Hence, Value-PP delivers an important contribution to the efficient use of phosphate and significantly contributes to the field of phosphate biotechnology.