Dextransucrase-catalyzed elongation of polysaccharide brushes with immobilized mono-/di-saccharides as acceptors

Biofilm-Integrated Glycosylated Membrane for Biosuccinic Acid Production

Biofilm-based cell-immobilized fermentation technology is regarded as the technique with the most potential for biobased product (chemicals, biofuelss materials, etc.) production in industry. Glycosylated membrane can mimic natural extracellular matrix (ECM) and improve cell adhesion and biofilm formation based on carbohydrate-microbial lectin interaction. Here, we applied glycosylated membrane with rhamnose modified surface for constructing Actinobacillus succinogenes biofilm and producing biosuccinic acid. Polymer hollow fiber (PHF) membrane surface was first modified by glycosylation based on physical adsorption approach. The approach is simple, green, and suitable for scale-amplification. Then, the microbial biofilm formed dramatically on the modified membrane surface. And for subsequent biosuccinic acid production, the maximum titer of succinic acid reached 67.3 g/L, and the yield was 0.82 g/g. Compared with free cell fermentation, the titer and yield increased by 18% and 9% in this biofilm-based cell-immobilized fermentation system, respectively. Importantly, the production efficiency of biosuccinic acid increased obviously for subsequent biofilm-based cell-immobilized fermentation. In addition, the biofilm-integrated glycosylated membrane showed high reusability for succinic acid production. This result is important for developing biofilms for a wide range of applications in bioproduct (chemicals, biofuels, materials, etc.) production.

Chemoenzymatic Synthesis of Branched Glycopolymer Brushes as the Artificial Glycocalyx for Lectin Specific Binding

The artificial glycocalyx fabricated by carbohydrates is of interest because it provides a platform to simulate the cell membranes that widely exist in the nature, and thus enable extensive applications to be implantable in bioengineering. Here, we present a green strategy combining two polymerization techniques, surface-initiated atom transfer radical polymerization (SI-ATRP) and enzyme-catalyzed elongation of polysaccharide, for fabricating densely packed branched glycopolymer brushes on the gold surface as the artificial glycocalyx. In this strategy, SI-ATRP is first performed to graft a linear polymer chain for anchoring maltose, which can be used as an enzyme acceptor for dextransucrase (DSase). Under DSase, a branched polysaccharide is efficiently formed through elongation of a sucrose substrate. Undoubtedly, enzymatic transglycosylation has unique advantages, such as being green, regio-, and stereo-selective, etc. The process of DSase-catalyzed polysaccharide is well monitored by a quartz crystal microbalance, and the grafting density of the glycopolymer brushes is estimated to be 0.7 chain nm^-2 with 23.0 nm dry thickness. The polysaccharide brushes display a branched structure consisting of α-d-glucose residues with 5% of α-1,3-linked shorter chain branches, and the branched structure is well characterized by X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, Fourier transform infrared/mirror reflection, water contact angle analysis, and atomic force microscopy. Compared with the linear maltose-anchored brushes, the branched glycopolymer analog prepared here shows high specific binding capacity of concanavalin A recognition, which should be of use in biomedical application.