Microbiology of sugar-rich environments: Diversity, ecology and system constraints

Microbial habitats that contain an excess of carbohydrate in the form of sugar are widespread in the microbial biosphere. Depending on the type of sugar, prevailing water activity and other substances present, sugar-rich environments can be highly dynamic or relatively stable, osmotically stressful, and/or destabilizing for macromolecular systems, and can thereby strongly impact the microbial ecology. Here, we review the microbiology of different high-sugar habitats, including their microbial diversity and physicochemical parameters, which act to impact microbial community assembly and constrain the ecosystem. Saturated sugar beet juice and floral nectar are used as case studies to explore the differences between the microbial ecologies of low and higher water-activity habitats respectively. Nectar is a paradigm of an open, dynamic and biodiverse habitat populated by many microbial taxa, often yeasts and bacteria such as, amongst many others, Metschnikowia spp. and Acinetobacter spp., respectively. By contrast, thick juice is a relatively stable, species-poor habitat and is typically dominated by a single, xerotolerant bacterium (Tetragenococcus halophilus). A number of high-sugar habitats contain chaotropic solutes (e.g. ethyl acetate, phenols, ethanol, fructose and glycerol) and hydrophobic stressors (e.g. ethyl octanoate, hexane, octanol and isoamyl acetate), all of which can induce chaotropicity-mediated stresses that inhibit or prevent multiplication of microbes. Additionally, temperature, pH, nutrition, microbial dispersion and habitat history can determine or constrain the microbiology of high-sugar milieux. Findings are discussed in relation to a number of unanswered scientific questions.

Use of water in aiding olefin/paraffin (liquid + liquid) extraction via complexation with a silver bis(trifluoromethylsulfonyl)imide salt

This paper describes the extraction of C₅–C₈ linear α-olefins from olefin/paraffin mixtures of the same carbon number via a reversible complexation with a silver salt (silver bis(trifluoromethylsulfonyl)imide, Ag[Tf₂N]) to form room temperature ionic liquids [Ag(olefin)_x][Tf₂N]. From the experimental (liquid + liquid) equilibrium data for the olefin/paraffin mixtures and Ag[Tf₂N], 1-pentene showed the best separation performance while C₇ and C₈ olefins could only be separated from the corresponding mixtures on addition of water which also improves the selectivity at lower carbon numbers like the C₅ and C₆, for example. Using infrared and Raman spectroscopy of the complex and Ag[Tf₂N] saturated by olefin, the mechanism of the extraction was found to be based on both chemical complexation and the physical solubility of the olefin in the ionic liquid ([Ag(olefin)_x][Tf₂N]). These experiments further support the use of such extraction techniques for the separation of olefins from paraffins.

Enhancing Liquid-Phase Olefin-Paraffin Separations Using Novel Silver-Based Ionic Liquids

This paper describes the extraction of C5-C8 linear α-olefins from olefin/paraffin mixtures of the same carbon number using silver(I)/N,N-dimethylbenzamide bis(trifluoromethylsulfonyl)imide ([Ag(DMBA)₂][Tf₂N]) or silver(I)/propylamine bis(trifluoromethylsulfonyl)imide ([Ag(PrNH₂)₂][Tf₂N]) as the extracting agent. The separation performance of the system increased with increasing chain length. [Ag(DMBA)₂][Tf₂N] appeared to outperform [Ag(PrNH₂)₂][Tf₂N] in terms of both selectivity and distribution coefficient. The [Ag(DMBA)₂][Tf₂N] system was successfully modeled using the universal quasi-chemical activity coefficient (UNIQUAC) model. These results support the potential future development of amine/amide-based ligands for producing soluble silver complexes useful for the separation of olefins from paraffins.

Plants Fagonia cretica L. and Hedera nepalensis K. Koch contain natural compounds with potent dipeptidyl peptidase-4 (DPP-4) inhibitory activity

Ethnopharmacological relevance
The two plants investigated here (Fagonia cretica L. and Hedera nepalensis K. Koch) have been previously reported as natural folk medicines for the treatment of diabetes but until now no scientific investigation of potential anti-diabetic effects has been reported. 

Materials and methods
In vitro inhibitory effect of the two tested plants and their five isolated compounds on the dipeptidyl peptidase 4 (DPP-4) was studied for the assessment of anti-diabetic activity. 

Results
A crude extract of Fagonia cretica possessed good inhibitory activity (IC₅₀value: 38.1 μg/ml) which was also present in its n-hexane (FCN), ethyl acetate (FCE) or aqueous (FCA) fractions. A crude extract of Hedera nepalensis (HNC) possessed even higher inhibitory activity (IC₅₀value: 17.2 μg/ml) and this activity was largely retained when further fractionated in either ethyl acetate (HNE; IC₅₀: 34.4 μg/ml) or n-hexane (HNN; 34.2 μg/ml). Bioactivity guided isolation led to the identification of four known compounds (isolated for the first time) from Fagonia cretica: quinovic acid (1), quinovic acid-3β-O-β-d-glycopyranoside (2), quinovic acid-3β-O-β-d-glucopyranosyl-(28→1)-β-d-glucopyranosyl ester (3), and stigmasterol (4) all of which inhibited DPP-4 activity (IC₅₀: 30.7, 57.9, 23.5 and >100 μM, respectively). The fifth DPP-4 inhibitor, the triterpenoid lupeol (5) was identified in Hedera nepalensis (IC₅₀: 31.6 μM). 

Conclusion
The experimental study revealed that Fagonia cretica and Hedera nepalensis contain compounds with significant DPP-4 inhibitory activity which should be further investigated for their anti-diabetic potential.

Olefin / Paraffin separation using Task-Specific Materials based on Ionic Liquids: Advances in Gas Processing

In this work, 1-hexene was extracted from its mixtures with n-hexane in varying ratios using a task specific ionic liquid. Herein, the ionic liquid (IL) 1-butyl-3-methylimidazolium nitrate, [BMIM][NO3], was used and examined with and without the addition of a metal salt. The impact of water on both selectivity and distribution coefficient was also tested. Four potential metal salts were investigated, the results of which demonstrate that the dissolution of transition-metal salts in the IL improves the separation of 1-hexene from n-hexane through metal-olefin complexation. Additionally, the presence of water in IL solutions containing metal salt enhances this selectivity. Finally, UNIFAC was used to correlate the experimental LLE data with good accuracy.