Exploring the Carbon/Electrolyte Interface in Supercapacitors Operating in Highly Concentrated Aqueous Electrolytes.

The development of superconcentrated or water-in-salt electrolytes (WISEs) has paved a new way toward realizing environmentally friendly, nonflammable batteries and supercapacitors based on aqueous electrolytes. The development of new electrolytes, such as WISEs, needs to be accompanied by further studies of the charging mechanism. This is essential to guide the choice of the electrode/electrolyte pairs for optimizing the performance of WISE-based supercapacitors. Therefore, to optimize the performance of carbon/carbon supercapacitors when using new, superconcentrated electrolytes, we present a detailed investigation of the carbon/electrolyte interface by combining electrochemical measurements with Raman and NMR spectroscopy and mass spectrometry. In particular, NMR provides crucial information about the local environment of electrolyte ions inside the carbon pores of the electrode. The results show that the structure of the electrolyte strongly depends on the concentration of the electrolyte and affects the mechanism of charge storage at the positive and negative electrodes.

Synthesis and Characterization of Sialylated Lactose- and Lactulose-Derived Oligosaccharides by Trypanosoma cruzi Trans-sialidase.

Sialylated oligosaccharides contribute 12.6-21.9% of total free oligosaccharides in human milk ( hMOS). These acidic hMOS possess prebiotic properties and display antiadhesive effects against pathogenic bacteria. Only limited amounts of sialylated hMOS are currently available. The aim of our work is to enzymatically synthesize sialylated oligosaccharides mimicking hMOS functionality. In this study, we tested mixtures of glucosylated-lactose (GL34), galactosylated-lactulose (LGOS), and galacto-oligosaccharide (Vivinal GOS) molecules, as trans-sialylation acceptor substrates. The recombinant trans-sialidase enzyme from Trypanosoma cruzi (TcTS) was used for enzymatic decoration, transferring (α2→3)-linked sialic acid from donor substrates to nonreducing terminal ß-galactopyranosyl units of these acceptor substrates. The GL34 F2 2-Glc-Lac compound with an accessible terminal galactosyl residue was sialylated efficiently (conversion degree of 47.6%). TcTS sialylated at least 5 LGOS structures and 11 Vivinal GOS DP3-4 compounds. The newly synthesized sialylated oligosaccharides are interesting as potential hMOS mimics for applications in biomedical and functional-food products.

Stimulatory effects of novel glucosylated lactose derivatives GL34 on growth of selected gut bacteria.

Previously we structurally characterized five glucosylated lactose derivatives (F1-F5) with a degree of polymerization (DP) of 3-4 (GL34), products of Lactobacillus reuteri glucansucrases, with lactose and sucrose as substrates. Here, we show that these GL34 compounds are largely resistant to the hydrolytic activities of common carbohydrate-degrading enzymes. Also, the ability of single strains of gut bacteria, bifidobacteria, lactobacilli, and commensal bacteria, to ferment the GL34 compounds was studied. Bifidobacteria clearly grew better on the GL34 mixture than lactobacilli and commensal bacteria. Lactobacilli and the commensal bacteria Escherichia coli Nissle and Bacteroides thetaiotaomicron only degraded the F2 compound α-D-Glcp-(1 → 2)-[ß-D-Galp-(1 → 4)-]D-Glcp, constituting around 30% w/w of GL34. Bifidobacteria digested more than one compound from the GL34 mixture, varying with the specific strain tested. Bifidobacterium adolescentis was most effective, completely degrading four of the five GL34 compounds, leaving only one minor constituent. GL34 thus represents a novel oligosaccharide mixture with (potential) synbiotic properties towards B. adolescentis, synthesized from cheap and abundantly available lactose and sucrose.

Structural characterization of glucosylated lactose derivatives synthesized by the Lactobacillus reuteri GtfA and Gtf180 glucansucrase enzymes.

Glucansucrase enzymes from lactic acid bacteria are receiving strong interest because of their wide range of gluco-oligosaccharide and polysaccharide products from sucrose, some of which have prebiotic potential. Glucansucrases GtfA and Gtf180 from Lactobacillus reuteri strains are known to convert sucrose into α-glucans with different types of linkages, but also to use other molecules as acceptor substrates. Here we report that incubation of (N-terminally truncated versions of) these enzymes with lactose plus sucrose resulted in synthesis of at least 5 glucosylated lactose products of a degree of polymerization (DP) of 3-4. Only glucansucrase Gtf180-ΔN also produced larger lactose-based oligosaccharides (up to DP9). Structural characterization of the glucosylated lactose products DP3-4 revealed glycosidic bonds other than (α1→4)/(α1→6) typical for GtfA-ΔN and (α1→3)/(α1→6) typical for Gtf180-ΔN: Both GtfA-ΔN and Gtf180-ΔN now introduced a glucosyl residue (α1→3)- or (α1→4)-linked to the non-reducing galactose unit of lactose. Both enzymes also were able to introduce a glucosyl residue (α1→2)-linked to the reducing glucose unit of lactose. These lactose derived oligosaccharides potentially are interesting prebiotic compounds.