Preparation of 5-Hydroxymethylfurfural from Glucose and Fructose in Ionic Liquids by Reactive Vacuum Distillation Over a Solid Catalyst

BACKGROUND: The production of 5-hydroxymethylfurfural (5-HMF) from biomass provides an alternative pathway for many commercial chemicals and polymers particularly for countries with high insolation such as sub-Saharan Africa. OBJECTIVE: The goal is continuous or semi-continuous dehydration of glucose and fructose to 5-HMF over a reusable castalyst in a process which is commmercial viable. METHOD: We deploy a separable and resuable catalyst, a low volatility solvent and reactive vacuum distillation. Results: Using a sulfated zirconia (SZ) catalyst in 1-butyl-3-methylimidazolium chloride [BMIM]Cl ionic liquid as solvent, we are able to separate the product by reactive vacuum distillation and obtain yields for 5-HMF of 82% and 65% at a 5 g experimental scale using fructose and glucose as substrates in a 2 h reaction time at 180 oC. The ionic liquid and SZ exhibited high activity when recycled for five successive trials. CONCLUSION: The low volatility solvent and solid catalyst allow for reactive vacuum distillation taking the sequence of steps from biomass such as Cassava to 5-HMF closer to commercial viability

Sea salt as a potential ocean mirror material

One way to increase planetary albedo in order to ameliorate global warming is to use ocean foams. The energy needed to maintain such foams, even if drawn from wave or wind is high and so they must be persistent, ideally surviving up to a month. While studying combinations of surfactants and gelling agents to make long-lived foams in salt water, it was apparent that some foams developed progressively higher reflectance as the upper surface dried. Scanning electron microscopy of the upper surface revealed 0.5 mm, near-monodisperse salt crystals. Thus with a refractive index of ∼1.5, sea salt, being in somewhat prodigious supply, now enters the arena as a potential mirror material. Its reflectance depends on the microstructure, specifically on the inhibition of Ostwald ripening. Studies were therefore carried out to investigate particle size effects in a membrane such as a foamed gel in which seawater dries on the upper surface. It was demonstrated that the organic additives used to create foam persistence also mediated sea salt crystallisation and in this way drastically modified the reflectance of the upper layer. These experiments suggest a new direction of research in planetary surface albedo modification

Hydrophobic Polymers from Food Waste: Resources and Synthesis

The food waste generated annually is approximately 1.3 Pg. It contains chemical feedstock that could be diverted to materials production as the mineral oil price rises, incurring no conflict over land use and providing new wealth-creating opportunities for food-producing countries. It potentially realigns the industrial and agricultural sectors of national economies. Food waste production scales with population as does demand for materials. This review builds upon previous landmark papers in Polymer Reviews that address biomass in polymer production. It surveys the current global food-waste resource and demonstrates how it could be used in the generation of hydrophobic polymers

pET expression vector customized for efficient seamless cloning

Here we present a modification of the widely used pET29 expression vector for use in rapid and straightforward parallel cloning via a gene replacement and Golden Gate strategy. The modification can be applied to other expression vectors for Gram-negative bacteria. We have used the modified vectors to clone large numbers of bacterial natural enzyme variants from genomic and metagenomic sources for applications in biocatalysis

Sustainable Synthesis of Chiral Tetrahydrofurans through the Selective Dehydration of Pentoses

L-Arabinose is an abundant resource available as a waste product of the sugar beet industry. Through use of a hydrazone-based strategy, L-arabinose was selectively dehydrated to form a chiral tetrahydrofuran on a multi-gram scale without the need for protecting groups. This approach was extended to other biomass-derived reducing sugars and the mechanism of the key cyclization investigated. This methodology was applied to the synthesis of a range of functionalized chiral tetrahydrofurans, as well as a formal synthesis of 3R-3-hydroxymuscarine

A metagenomics approach for new biocatalyst discovery: application to transaminases and the synthesis of allylic amines

Transaminase enzymes have significant potential for the sustainable synthesis of amines using mild aqueous reaction conditions. Here a metagenomics mining strategy has been used for new transaminase enzyme discovery. Starting from oral cavity microbiome samples, DNA sequencing and bioinformatics analyses were performed. Subsequent in silico mining of a library of contiguous reads built from the sequencing data identified 11 putative Class III transaminases which were cloned and overexpressed. Several screening protocols were used and three enzymes selected of interest due to activities towards substrates covering a wide structural diversity. Transamination of functionalized cinnamaldehydes was then investigated for the production of valuable amine building blocks

Regioselective Dehydration of Sugar Thioacetals under Mild Conditions

Sugars are abundant in waste biomass, making them sustainable chiral building blocks for organic synthesis. The demand for chiral saturated heterocyclic rings for pharmaceutical applications is increasing as they provide well-defined three-dimensional frameworks that show increased metabolic resistance. A range of sugar thioacetals can be dehydrated selectively at C-2 under mild basic conditions, and the resulting ketene thioacetals can be applied to the production of useful chiral building blocks via further selective dehydration reactions

A rapid, sensitive colorimetric assay for the high-throughput screening of transaminases in liquid or solid-phase

A new colorimetric method has been developed to screen transaminases using an inexpensive amine donor. The assay is sensitive, has a low level of background coloration, and can be used to identify and profile transaminase activities against aldehyde and ketone substrates in a high-throughput format. Significantly it is also amendable to solid phase colony screening

Direct Conversion of Hydrazones to Amines using Transaminases

Transaminase enzymes (TAms) have been widely used for the amination of aldehydes and ketones, often resulting in optically pure products. In this work, transaminases were directly reacted with hydrazones in a novel approach to form amine products. Several substrates were investigated, including those with furan and phenyl moieties. It was determined that the amine yields increased when an additional electrophile was added to the reaction mixture, suggesting that they can sequester the hydrazine released in the reaction. Pyridoxal 5’-phosphate (PLP), a cofactor for transaminases, and polyethylene glycol (PEG)-aldehydes were both found to increase the yield of amine formed. Notably, the amination of (S)-(−)-1-amino-2-(methoxymethyl)pyrrolidine (SAMP) hydrazones gave promising results as a method to form chiral β-substituted amines in good yield

Furfurylamines from biomass: Transaminase catalysed upgrading of furfurals

Furfural is recognised as an attractive platform molecule for the production of solvents, plastics, resins and fuel additives. Furfurylamines have many applications as monomers in biopolymer synthesis and for the preparation of pharmacologically active compounds, although preparation via traditional synthetic routes is not straightforward due to by-product formation and sensitivity of the furan ring to reductive conditions. In this work transaminases (TAms) have been investigated as a mild sustainable method for the amination of furfural and derivatives to access furfurylamines. Preliminary screening with a recently reported colorimetric assay highlighted that a range of furfurals were readily accepted by several transaminases and the use of different amine donors was then investigated. Multistep synthetic routes were required to synthesise furfurylamine derivatives for use as analytical standards, highlighting the benefits of using a one step biocatalytic route. To demonstrate the potential of using TAms for the production of furfurals, the amination of selected compounds was then investigated on a preparative scale