Research highlights

 

Research highlight: Micro delivery service for fertilizers

Micro delivery service for fertilizers Wiley-VCH

Plants can absorb nutrients through their leaves as well as their roots. However, foliar fertilization over an extended period is difficult. In the journal Angewandte Chemie, German researchers have now introduced an efficient delivery system for micronutrients based on biohybrid microgels. Special peptides anchor the "microcontainers" onto the leaf surface while binding sites inside ensure gradual release of the "cargo".

Foliar fertilization is already commonly used in areas such as viniculture, when the leaves on the vines turn yellow due to a mineral deficiency. Yet, despite the use of detergents, adhesives, and humectants, controlled delivery of nutrients through foliar fertilization over several weeks is nearly impossible to achieve. Up to 80% of the nutrients are washed away, winding up in the soil and being converted into forms that the plant cannot use. In addition, they can be washed into bodies of water and cause environmental problems. An additional problem is that strong sunlight evaporates the water out of the applied fertilizer solution. This results in a high salt concentration that draws water out of the leaf and causes burn damage.

A team from DWI-Leibniz Institute for Interactive Materials in Aachen, RWTH Aachen University, and the University of Bonn has now developed a foliar fertilization system based on biocompatible microgels that adhere selectively to leaves for a long period and slowly deliver nutrients in a controlled fashion. Microgels are tiny particles of cross-linked macromolecules that can bind water and other molecules, such as fertilizers very efficiently.

Led by Ulrich Schwaneberg, Andrij Pich and Felix Jakob, the researchers equipped the interiors of gel particles with binding sites modeled on the iron-binding proteins of bacteria. These ensure that the iron ions are released slowly. The microgels are loaded with an iron-containing solution at a pH of 3. When the pH rises to 7, the microgels shrink, releasing water and binding the iron.

The surface of the gel particles is equipped with anchor peptides from lactic acid bacteria. These bind securely to leaf surfaces to hinder rinsing away of the microgels. The water in the gel provides an aqueous microenvironment that allows the iron to diffuse into the leaves. Yellow leaves of iron-deficient cucumber plants rapidly turned green in spots where the new foliar fertilizer was applied.

By incorporating different binding sites, the microgel "containers" can be loaded with a multitude of other metal ions or agents. A controlled delivery of agents as required would minimize the applied quantities as well as the release of fertilizers and pesticides into the environment. Low production costs, high levels of loading, easy application, and adjustable adhesive properties should make broad industrial applications possible. The goal is to make self-regulating delivery systems for sustainable agriculture.

Richard A. Meurer et al, Biofunctional Microgel-Based Fertilizers for Controlled Foliar Delivery of Nutrients to Plants, Angewandte Chemie International Edition (2017). DOI: 10.1002/anie.201701620

Read more

 
 

Generation of building blocks for synthesis of filter membranes

Generation of building blocks for synthesis of filter membranes Bio VI

The iron transporter FhuA - Ferric hydroxamate uptake protein component A is a channel protein produced by the bacterium Escherichia coli which was tailored for the generation of synthetic membranes using FhuA proteins and polymers. The FhuA protein forms a permeable channel with a uniform pore size from 2.5 to 3.0 nm and a barrel-like structure. Lysine residues were specifically located in a rim on the outer surface of the channel above the transmembrane region for the attachment of polymer chains. This design enabled the grafting of PNIPAAm polymer chains from the outer FhuA channel surface. In the future, the synthesized building blocks of the FhuA channel proteins and polymer chains will be used for generation of hybrid membranes for nanofiltration processes. These generated membranes can be applied in the downstream processing as molecular sieves for the separation of different components which is essential for synthesizing sweeteners, pesticides and pharmaceuticals.

Read more

 
 

In vitro flow cytometry-based screening platform for cellulase engineering

In vitro flow cytometry-based screening platform for cellulase engineering Bio VI

Screening technologies are of pivotal importance for tailoring biocatalysts in directed evolution, as millions of mutant enzyme variants could be generated in every trial. Hence, ultrahigh throughput screening techniques have been developed in order to still complete such trials in a reasonable amount of time. These techniques are well capable of analyzing up to 107 events per hour and thus can analyze the complete coverage of a generated protein sequence with high efficiency.

This technology becomes even more powerful if it is coupled with a cell-free enzyme expression technique. This expression method enables the experimentator to reduce diversity loss when transforming mutant libraries into expression hosts, to design enzymes of animal or human origin or even perform directed evolution of toxic enzymes.

The first ever combination of such a cell-free compartmentalization platform with a flow cytometry-based screening has been achieved in the InVitroFlow technology and successfully applied to directed evolution of cellulose enzymes.

Read more

 
 

Screening through the PLICable promoter toolbox enhances protein production in Escherichia coli

Screening through the PLICable promoter toolbox enhances protein production in Escherichia coli Bio VI

Escherichia coli is a common host for recombinant protein production in which product titers are highly dependent on the employed expression system. Thereby, promoters are a key element to control gene expression levels. In this study, a novel PLICable promoter toolbox was developed. It enables the identification of the most suitable promoter out of ten IPTG-inducible promoters (T7, A3, lpp, tac, pac, Sp6, lac, npr, trc and syn) for high level protein production in a single cloning step and after a screening experiment.

Read more