Influence of Hierarchical Interfacial Assembly on Lipase Stability and Performance in Deep Eutectic Solvent

Correlating Bromelain's activity with its structure and active-site dynamics and the medium's physical properties in a hydrated deep eutectic solvent

Deep eutectic solvents (DESs) are emerging as new media of choice for biocatalysis due to their environmentally friendly nature, fine-tunability, and potential biocompatibility. This work deciphers the behaviour of bromelain in a ternary DES composed of acetamide, urea, and sorbitol at mole fractions of 0.5, 0.3, and 0.2, respectively (0.5Ac/0.3Ur/0.2Sor), with various degrees of hydration. Bromelain is an essential industrial proteolytic enzyme, and the chosen DES is non-ionic and liquid at room temperature. This provides us with a unique opportunity to contemplate protein behaviour in a non-ionic DES for the very first time. Our results infer that at a low DES concentration (up to 30% V/V DES), bromelain adopts a more compact structural conformation, whereas at higher DES concentrations, it becomes somewhat elongated. The microsecond conformational fluctuation time around the active site of bromelain gradually increases with increasing DES concentration, especially beyond 30% V/V. Interestingly, bromelain retains most of its enzymatic activity in the DES, and at some concentrations, the activity is even higher compared with its native state. Furthermore, we correlate the activity of bromelain with its structure, its active-site dynamics, and the physical properties of the medium. Our results demonstrate that the compact structural conformation and flexibility of the active site of bromelain favour its proteolytic activity. Similarly, a medium with increased polarity and decreased viscosity is favourable for its activity. The presented physical insights into how enzymatic activity depends on the protein structure and dynamics and the physical properties of the medium might provide useful guidelines for the rational design of DESs as biocatalytic media.

Reviewing research on the synthesis of CALB-catalyzed sugar esters incorporating systematic mapping principles

Rigorous evidence reviews must follow specific guidelines designed to improve transparency, reproducibility, and to minimize biases to which traditional reviews are susceptible. While evidence synthesis methods, such as systematic reviews and maps, have been used in several research fields, the majority of reviews published in the realm of chemical engineering are nonsystematic. In this study, we incorporated principles of systematic mapping to conduct a literature review covering research on the synthesis of sugar fatty acid esters (SFAE) with Candida antarctica lipase B (CALB). Our results showed that the simple monosaccharides were the most cited sugars among studies we conducted. The direct use of renewable raw materials and frequently available resources to produce alternative sugar esters (SE) was scarcely reported in our data set. We found that free fatty acids (FFA) were the most commonly cited acyl donors amongst all publications, with lauric, oleic, and palmitic acids accounting for ∼43% of the occurrences. Tertiary alcohols (ter-butyl alcohol (T-but) and 2-methyl-2-butanol (2M2B)) and ionic liquids were the most used solvents to synthesize SE. The co-occurence analysis of keywords involving solvent terms showed that most of the papers evaluated different solvents as reaction media (mostly in the form of a bisolvent system), also investigating the impact of their choice on sugar ester productivities. Given the potential of reviews informing us of research decisions, this article reveals trends and spaces across CALB-catalyzed SE synthesis research, in addition to introducing a new methodological perspective for developing reviews in the field of chemical engineering.

Enzyme-Adsorbed Chitosan Nanogel Particles as Edible Pickering Interfacial Biocatalysts and Lipase-Responsive Phase Inversion of Emulsions

Here, a simple food-grade Pickering emulsion system is prepared and adopted for biphasic biocatalytic reactions. The chitosan nanogels were prepared with strong dispersion of chitosan aggregates approaching neutral pH and then used as the particle emulsifiers to produce oil-in-water Pickering emulsions. The chitosan nanogel exhibited high affinity to negatively charged lipase. As a result of increasing the biphasic interfacial area and loading amount on the oil-water interface, the catalysis activity of lipase and recycling and pH stability were highly enhanced through colorimetric determination of p-nitrophenol (the hydrolysis product of p-nitrophenyl palmitate). A general strategy was proposed to obtain stimulus-responsive Pickering emulsions that can undergo phase inversion. The in situ modification of the wettability of chitosan nanogel could be attributed to the interaction between nanogel and free fatty acids, which was triggered by lipase hydrolysis. This would permit a rapid and controlled release of hydrophobic active components in response to enzymatic triggers.

Deep eutectic solvents for biocatalytic transformations: focused lipase-catalyzed organic reactions

Biocatalysis is a green and sustainable technology for which the ideal solvent should be nontoxic, biocompatible, biodegradable, and sustainable, in addition to supporting high enzyme activity and stability. Deep eutectic solvents (DESs), a novel class of green solvents, have recently emerged as excellent alternatives for use in various biocatalytic reactions and, in particular, in lipase-catalyzed reactions with enzymes. This review discusses the achievements that have been made so far in the use of DESs as reaction media for lipase-catalyzed reactions. In addition, the application of DESs in esterification, transesterification, and amidation reactions with isolated or immobilized biocatalysts, toward enabling the synthesis of biodiesels, sugar esters, phenolipids, and fatty acyl ethanolamides, is summarized, while advances in lipase-catalyzed chemoenzymatic epoxidation reactions, C-C bond-forming Aldol reactions, and hydrolysis reactions in DESs are also discussed. This review also summarize some remaining questions concerning the use of DESs, including the intriguing role of water as a cosolvent in biocatalytic reactions carried out in DESs, and the relationship between the nature of the DESs and their influence on the enzyme stability and activity at the molecular level.

Influence of Betaine- and Choline-based Eutectic Solvents on Lipase Activity

Background:

Eutectic solvents are a mixture of two compounds which possess a lower melting temperature than the parent compounds, using quaternary ammonium salts, such as choline chloride and betaine hydrochloride and organic acids, polyols and amides as hydrogen bond donors. These solvents can be an alternative as non-aqueous media for enzymatic reactions, mainly using lipases.

Objective:

The objective of this work is to evaluate enzymatic activity and stability of commercial lipases, immobilized or at free form (Thermomyces lanuginosus: Lipozyme TL IM, iTL and Lipolase 100 L, fTL; Candida antarctica: Novozym 435, iCALB; Novozym 735, iCALA and Novozym CALB L, fCALB); and a phospholipase (Lecitase Ultra), in the presence of eutectic solvents (choline chloride ChCl:urea, ChCl:glycerol, betaine hydrochloride (BeHCl):urea and BeHCl: glycerol.

Methods:

Initially, lipases were maintained for 2 hours in solutions of choline and betaine-based eutectic solvents (1 to 20% m/m) at 25ºC compared with water for relative enzymatic activity. Using the solvent that best promoted lipase activity, some parameters were evaluated such as the molar ratio between quaternary ammonium salts and urea, stocking temperature and kinetics.

Results and Conclusion:

These eutectic solvents enable, mainly with immobilized lipases, 25 to 125 times more activity than water at 25ºC and 2h, and even after 24h, lipase iTLL was still 40 times more active in the presence of ChCl:Urea 1:3. Lipase iCALB showed great thermostability 47 times higher at 55ºC, almost double relative activity at 25ºC in the presence of BetHCl:Urea 1:4.

Transforming food waste: how immobilized enzymes can valorize waste streams into revenue streams

Food processing generates byproduct and waste streams rich in lipids, carbohydrates, and proteins, which contribute to its negative environmental impact. However, these compounds hold significant economic potential if transformed into revenue streams such as biofuels and ingredients. Indeed, the high protein, sugar, and fat content of many food waste streams makes them ideal feedstocks for enzymatic valorization. Compared to synthetic catalysts, enzymes have higher specificity, lower energy requirement, and improved environmental sustainability in performing chemical transformations, yet their poor stability and recovery limits their performance in their native state. This review article surveys the current state-of-the-art in enzyme stabilization & immobilization technologies, summarizes opportunities in enzyme-catalyzed valorization of waste streams with emphasis on streams rich in mono- and disaccharides, polysaccharides, lipids, and proteins, and highlights challenges and opportunities in designing commercially translatable immobilized enzyme systems towards the ultimate goals of sustainable food production and reduced food waste.

Synthesis and characterization of lactose fatty acid ester biosurfactants using free and immobilized lipases in organic solvents

In this work, lactose fatty acid esters were enzymatically synthesized from fatty acids and lactose using Candida antarctica B lipase (CALB) in organic solvents. Products were purified using a solvent extraction method and analyzed using ATR-FTIR and surface-active properties measurements. Results showed that hexanes and acetonitrile provide the highest conversions for both free and immobilized lipases, up to 77% and 93% respectively. The conversion rate of esterification is solvent-dependent for free lipase; the conversion rate of immobilized lipase still shows solvent dependency, but to a lesser degree. Surface tension, interfacial tension, critical micelle concentration (CMC), and contact angles were also measured for all of the samples, showing the potentials of these sugar esters as naturally derived surfactants for the food industry.

Stabilization of Lipase in Polymerized High Internal Phase Emulsions

Candida antarctica lipase B is stabilized in a porous, high internal phase emulsion (HIPE) of polydicyclopentadiene to enable biocatalytic waste stream upcycling. The immobilized lipase is subjected to thorough washing conditions and tested for stability in extreme environments and reusability. A porous internal microstructure is revealed through scanning electron microscopy. After preparation, lipase activity increased to 139 ± 9.7% of its original activity. After 10 cycles of reuse, immobilized lipase retains over 50% activity. Immobilized lipase retains activity after 24 h of exposure to temperatures ranging from 20 to 60 °C and pH values of 3, 7, and 10. In the most extreme environments tested, lipase retained 42.8 ± 21% relative activity after exposure to 60 °C and 49.4 ± 16% relative activity after exposure to pH 3. Polymerized HIPEs stabilize lipase and, thus, extend its working range. Further synthesis optimization has the potential to increase enzyme stability, immobilization efficiency, and uniformity. The reported hierarchical stabilization technique shows promise for use of immobilized lipase in non-ideal, industrially relevant conditions.