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Für eine nachhaltige Bioökonomie

Forschen • Ausbilden • Vernetzen
Für eine nachhaltige Bioökonomie
BOOST FUND Projekt PhytaPhoS

Optimizing the Phosphorus Cycle in the Sugar Beet Production Process by Phytase Supplement


The BioSc funded project PhytaPhoS focused on optimizing the sugar beet production process by addition of phytases. The thereby obtained phytate reduced sugar beet slices and a phosphate enriched spent lime are highly interesting for the farmers as well as the breeders.

At first in WP1 the identification of phytases which are active in the sugar beet matrix was tackled. The E. coli phytase has been selected for the follow up mutagenesis and was produced to supply enough material to the partners. Subsequently, enzyme engineering approaches were performed. Though directed evolution, signal peptide investigations and recombination libraries, phytase variants with improved thermal resistance, increased expression and active in sugar beet extract were identified. In addition, phytase immobilization on a support and first separation from the media were demonstrated which allow the efficient application of the phytase in the sugar beet production process.

In WP2 P-enriched spent lime was produced. Dicalciumphosphat (CaHPO4) was found to be the main phosphate fraction in spent limes. This form of P is nearly insoluble in water. The availability for plants was tested in WP3. Laboratory tests showed that the proportion of phosphate dissolved with sugar extraction was much higher than data from the literature suggest. On the other hand, the remaining P-residue in the extracted sugar beet pulp and above all the phytin P fraction was significantly lower than described in the literature. The yield of additional P after treatment of sugar beet pulp with phytase enzymes was therefore much lower than expected. It is possible that the phytase content of modern sugar beet varieties has declined significantly over the last decades due to breeding measures. In order to verify this, old varieties would have to be analyzed. However, these are no longer cultivated today.

In WP3, the efficiency of the P-enriched spent lime as a fertilizer was assessed by providing the product to sugar beet and maize during juvenile growth. Phosphorus from P-enriched spent lime was plant available, as shown by biomass increase and phosphorus concentrations of plant tissues. However, the efficiency of P-enriched spent lime was not as good as from commercial P-fertilizers. This could in part be attributed to pH modification and an impeding effect by spent lime on plant development, root growth and P-uptake. An increase in phosphorus concentration per amount of applied spent lime reduced the inhibiting effect.

In WP4, both, a private cost-benefit analysis (CBA) with reference to an average sugar factory, as well as a social CBA witch analysis of the impacts to society added to the private effects, had been prepared. Based on the data available in the literature on the phytin content in sugar beet, both calculations showed highly-lucrative results. Based on the phytin content in sugar beet determined in WP2, the private CBA shows hardly any positive effect, but the social CBA does. To protect the environment, the use of enzymes in sugar production would be worthwhile in any case.

Closing nutrient cycles in sugar production. Flow of phosphorus without (left) and with use of a thermally stable phytase (right).

 Participating Core Groups

Prof. Dr. Mathias Becker, Prof. Dr. Heiner Goldbach, Dr. Ute Arnold, Dr. Manfred Trimborn; Institute of Crop Science and Resource Conservation (INRES), Plant nutrition; University of Bonn
Prof. Dr. Ulrich Schurr, Dr. Nicolai Jablonowski, Institute of Bio- and Geosciences IBG-2: Plant Sciences, Forschungszentrum Jülich GmbH
Prof. Dr. Ulrich Schwaneberg, Prof. Dr. A. Pich, Dr. Anna Joelle Ruff; Institute of Biotechnology (Bio VI, Biotechnology); RWTH Aachen University.

Prof. Dr. Mathias Becker
; Institute of Crop Science and Resource Conservation (INRES), Plant nutrition; University of Bonn

Dr. Manfred Trimborn
, INRES - Pflanzenernährung
University of Bonn
Karlrobert-Kreiten-str. 13
53359 Bonn
phone: +49 (0) 228 – 73 3639

Project duration

01.04.2015 – 31.03.2018


PhytaPhoS is part of the NRW-Strategieprojekt BioSC and thus funded by the Ministry of Innovation, Science and Research of the German State of North Rhine-Westphalia.