Selective Production and Analysis of Poly(γ-glutamic acid) with Distinct Molecular Weight Distribution and Composition
Poly(γ-glutamic acid) (PGA) is an anionic, water-soluble, biodegradable, edible, and nontoxic biopolymer produced by different Bacillus species. PGA consists of up to 10,000 D- and/or L-glutamic acid monomers and can be characterized by its molecular weight distribution and the ratio and sequence of D- to L-glutamic acid subunits. In contrast to proteins, where amino acids are bound by α-amide linkages, glutamic acid monomers in PGA are linked by γ-peptide bonds making it stable against proteases. A great variety of possible applications exist for PGA, e.g., in the food and skin care industry, in wastewater treatment, or in the pharmaceutical industry. Microbial produced PGA by Bacillus species has a high molar mass of 100-10,000 kDa and a broad polydispersity. However, for pharmaceutical applications, such as conjugates, nanoparticles, and hydrogels, a specific molecular weight and a narrow polydispersity as well as certain D/L ratios or pure D- or L-PGA are crucial.
The project aims at the selective synthesis of tailored PGA, with a defined composition of D- and L-glutamate as well as specific molecular weight and weight distributions. The project will make use of the joined expertise of the participating cooperation partners. The Blank group will be responsible for the genetic engineering of Bacillus strains for production of tailored PGA by applying different genetic strategies. All genetic engineering approaches aim at increased product selectivity and require a detailed analysis of the altered whole-cell biocatalyst by process monitoring and engineering. Therefore, the Büchs group will perform microbial cultivations in shake flasks and stirred tank reactors using online monitoring devices for process control. Online signals and data from offline samples will be used for characterization and optimization of the production process. Thorough analysis of the product characteristics such as D/L ratio, molecular weight and distribution of molecular weight will be performed. For deeper insights into the PGA production pathway and regulatory network, detailed metabolome analyses will be conducted by the Fukusaki group.
Prof. L. M. Blank, RWTH Aachen / Prof. E. Fukusaki, Osaka University
International Research Training Group “Selectivity in Chemo and Biocatalysis - SeleCa” (GRK 1628) funded by DFG (Deutsche Forschungsgemeinschaft)