Elucidating enzymatic polymerisations : Chain-length selectivity of Candida antarctica lipase B towards various aliphatic diols and dicarboxylic acid diesters

The sustainable synthesis of polymers is a field with growing interest due to the need of modern society to preserve the environment whilst making used products and food sustainable for the future generations. In this work we investigate the possibility of synthesizing aliphatic polyesters derived from various dicarboxylic acid diesters and diols in a solvent-free reaction system. Candida antarctica lipase B was selected as biocatalyst and its selectivity towards the carbon and ester chain length were elucidated. The selected enzyme was able to synthesize various polyesters combining C4-C10 diesters and C4-C8 diols. All combinations led to monomer conversions above 90% in 24 h with the best number average molecular weights (Mn) being obtained through the combination of dimethyl adipate and 1,8-octanediol leading to a Mn of 7141 Da. Differential scanning calorimetry analysis shows a clear trend with an increase in melting temperature of the polymers that correlates with both the increase of the Mn or of the polymer's constitutional repeat unit carbon chain length. Thermogravimetric analysis and rheology measurements performed on selected samples also confirm the trend showing a variation of the polymer's degradation temperatures and viscosity profiles

Deep Eutectic Solvents Based on Natural Ascorbic Acid Analogues and Choline Chloride

Deep eutectic solvents (DES) are one of the most promising green technologies to emerge in recent years given their combination of environmentally friendly credentials and useful functionalities. Considering the continued search for new DES -- especially those that exemplify the aforementioned characteristics, we report the preparation of DES based on natural analogues of L-ascorbic acid for the first time. The onset of eutectic melting occurred at temperatures far below the melting point of the individual components and resulted in the generation of glass forming fluids with glass transition temperatures, viscosities and flow behavior that are comparable to similar systems. This work expands the current array of DES that can be produced using naturally occurring components, which given their potential to be bio-derived, interesting physicochemical properties (e.g. propensity to supercool and vitrify) and apparent antibacterial nature, may provide utility within a range of applications

Unforeseen crystal forms of the natural osmolyte floridoside

Floridoside (2-α-O-D-galactopyranosyl glycerol) is a glycerol glycoside that is biosynthesised by most species of red algae and has been implicated as an intracellular regulator of various homeostatic functions. Here, we report the identification of two unforeseen crystal forms of the ubiquitous natural osmolyte floridoside including a seemingly unheralded second anhydrous conformational polymorph and the unambiguous description of an elusive monohydrated variant. By employing a variety of thermal and spectroscopic techniques, we begin to explore both their macro and molecular physicochemical properties, which are notably different to that of the previously reported polymorph. This work advances the characterisation of this important natural biomolecule which could aid in facilitating optimised utilisation across a variety of anthropocentric applications and improve comprehension of its role in-vivo as a preeminent compatible solute

Water activity in liquid food systems : A molecular scale interpretation

Water activity has historically been and continues to be recognised as a key concept in the area of food science. Despite its ubiquitous utilisation, it still appears as though there is confusion concerning its molecular basis, even within simple, single component solutions. Here, by close examination of the well-known Norrish equation and subsequent application of a rigorous statistical theory, we are able to shed light on such an origin. Our findings highlight the importance of solute-solute interactions thus questioning traditional, empirically based “free water” and “water structure” hypotheses. Conversely, they support the theory of “solute hydration and clustering” which advocates the interplay of solute-solute and solute-water interactions but crucially, they do so in a manner which is free of any estimations and approximations