Rheological characterization of the exopolysaccharide Paenan in surfactant systems.

Rheology-controlling agents are of importance for numerous products in a variety of industries. Replacement of synthetic chemicals with natural additives is desired in light of current environmental awareness and limited fossil resources. This study investigates the rheological features of Paenan, an exopolysaccharide produced by Paenibacillus polymyxa. Paenan exhibits highly shear-thinning flow behavior at concentrations ≥0.1% in 0.5% NaCl. Because of its pronounced intermolecular network, it forms stable, weak gels, thereby delivering elasticity as well as thixotropy. Application-relevant flow behavior is obtained with 60-65% less polymer as compared to the benchmark commercial products Xanthan and Gellan. In mixtures with surfactants (sodium lauryl ether sulfate, cetrimonium chloride, cocamidopropyl betaine, or lauryl glucoside), Paenan displays outstanding compatibility with every class of surfactant, making it superior to the partially incompatible Xanthan and Gellan. The weak-gel character of Paenan/surfactant systems is retained with three out of four surfactants, rendering Paenan highly interesting for various applications.

Tailor-made exopolysaccharides-CRISPR-Cas9 mediated genome editing in Paenibacillus polymyxa.

Application of state-of-the-art genome editing tools like CRISPR-Cas9 drastically increase the number of undomesticated micro-organisms amenable to highly efficient and rapid genetic engineering. Adaptation of these tools to new bacterial families can open up entirely new possibilities for these organisms to accelerate as biotechnologically relevant microbial factories, also making new products economically competitive. Here, we report the implementation of a CRISPR-Cas9 based vector system in Paenibacillus polymyxa, enabling fast and reliable genome editing in this host. Homology directed repair allows for highly efficient deletions of single genes and large regions as well as insertions. We used the system to investigate the yet undescribed biosynthesis machinery for exopolysaccharide (EPS) production in P. polymyxa DSM 365, enabling assignment of putative roles to several genes involved in EPS biosynthesis. Using this simple gene deletion strategy, we generated EPS variants that differ from the wild-type polymer not only in terms of monomer composition, but also in terms of their rheological behavior. The developed CRISPR-Cas9 mediated engineering approach will significantly contribute to the understanding and utilization of socially and economically relevant Paenibacillus species and extend the polymer portfolio.

Controlled production of polysaccharides-exploiting nutrient supply for levan and heteropolysaccharide formation in Paenibacillus sp.

Bacterial exopolysaccharides (EPSs) are promising sustainable alternatives to synthetic polymers. Here we describe the production and characterization of different EPSs produced by the recently isolated Paenibacillus sp. 2H2. A final EPS titer of 4.54gL(-1) was recovered after a 17-h fermentation, corresponding to a volumetric productivity of 0.27gL(-1)h(-1). Remarkably, supplying the fermentation with specific carbon and nitrogen sources could be exploited for the production of different polymers. A pure heteropolysaccharide composed of glucose, mannose, galactose, and glucuronic acid (3.5:2:1:0.1) was obtained when using glucose/glycerol and peptone as substrates. A pure levan-type polymer or mixture of both polymers was observed with sucrose and NaNO3 or peptone. To our knowledge, this is the first report that nutrients, particularly nitrogen sources, can be used to fine-tune EPS production in Paenibacillaceae. Rheological characterization of the heteropolysaccharide revealed impressive thickening properties, suggesting its potential application in commodity materials.