Deactivation and unfolding are uncoupled in a bacterial lipase exposed to heat, low pH and organic solvents

Biointerface mineralization generates ultraresistant gut microbes as oral biotherapeutics

Despite the fact that oral microecologics are effective in modulating the gut microbiome, they always suffer from multiple insults during the journey from manufacture to arrival at the intestine. Inspired by the protective mechanism of mineralization, we describe a cytocompatible approach of biointerface mineralization that can generate an ultraresistant and self-removable coating on bacterial surface to solve these challenges. Mineral coating endows bacteria with robust resistances against manufacture-associated oxygen exposure, ultraviolet irradiation, and 75% ethanol. Following oral ingestion, the coating is able to actively neutralize gastric acid and release encapsulated bacteria through spontaneous yet rapid double-decomposition reaction. In addition to acid neutralization, the generated calcium ions can trigger micellar aggregation of bile acid, enabling dual exemptions from the insults of gastric acid and bile acid to achieve uncompromised bacterial viability. Further supported by the therapeutic efficacy of coated bacteria toward colitis mice, biointerface mineralization provides a versatile platform for developing next-generation living oral biotherapeutics.

Rebuilding the lid region from conformational and dynamic features to engineering applications of lipase in foods: Current status and future prospects

The applications of lipases in esterification, amidation, and transesterification have broadened their potential in the production of fine compounds with high cumulative values. Mostly, the catalytic triad of lipases is covered by either one or two mobile peptides called the "lid" that control the substrate channel to the catalytic center. The lid holds unique conformational allostery via interfacial activation to regulate the dynamics and catalytic functions of lipases, thereby highlighting its importance in redesigning these enzymes for industrial applications. The structural characteristic of lipase, the dynamics of lids, and the roles of lid in lipase catalysis were summarized, providing opportunities for rebuilding lid region by biotechniques (e.g., metagenomic technology and protein engineering) and enzyme immobilization. The review focused on the advantages and disadvantages of strategies rebuilding the lid region. The main shortcomings of biotechnologies on lid rebuilding were discussed such as negative effects on lipase (e.g., a decrease of activity). Additionally, the main shortcomings (e.g., enzyme desorption at high temperatre) in immobilization on hydrophobic supports via interfacial action were presented. Solutions to the mentioned problems were proposed by combinations of computational design with biotechnologies, and improvements of lipase immobilization (e.g., immobilization protocols and support design). Finally, the review provides future perspectives about designing hyperfunctional lipases as biocatalysts in the food industry based on lid conformation and dynamics.

Enzymatic hydrolysis and extraction of ginsenoside recovered from deep eutectic solvent-salt aqueous two-phase system

Rare ginsenoside CK was recognized as a popular functional food because of superior pharmacological activity, but it is restricted by further applications by the difficulty in preparation. In this study, deep eutectic solvent (DES)-based aqueous two-phase system (ATPS) was established to transform and extract ginsenoside CK in situ for the first time. The phase formation conditions for preparing ATPS using choline chloride-based DES were studied, and the optimal conditions for extractive bioconversion were explored using conventional single-factor experiments. The conditions for ATPS establishment were as follows: 31.9% (w/w) DES (ChCl-ethylene glycol)/24.5% (w/w) K₂HPO₄, 55 °C, pH 5.0. Under the optimal conditions, 75.79% product and 61.14% β-glucosidase were recovered from the top and bottom phase, respectively. In addition, DES and β-glucosidase can be recovered and recycled again for the next extractive bioconversion of CK. These results indicated that this green and efficient method exhibited considerable value in integrated production and extraction processes, and demonstrated the potential for obtaining highly recycled functional foods and similar products.

Lipase catalysed biodiesel synthesis with integrated glycerol separation in continuously operated microchips connected in series

Although the application of microreactors in different processes has been extensively explored in recent decades, microreactors continue to be underexplored in the context of the enzyme-catalysed process for biodiesel production. Due to their numerous advantages, microreactors could become the next step in the development of a biodiesel production process characterised by sustainability, cost-effectiveness and energy efficiency. In this investigation, biodiesel production was catalysed by lipase from Thermomyces lanuginosus (Lipolase L100). Edible sunflower oil was used as a model substrate in order to investigate the process. After optimal process conditions had been determined, waste-cooking oil was used for biodiesel production to make the production process more sustainable. Three different substrate-feeding strategies were investigated and finally an optimal strategy was proposed. In all the investigated systems, fatty acids methyl esters (FAME) content was higher than 95% and obtained in a significantly shorter time (less than 2 h) compared to the batch process in which biodiesel production was catalysed by lipase (C = 95%, t = 96 h). After the optimal biodiesel production system had been proposed, an integrated system with two microchips connected in series was developed. The first microchip was used for biodiesel production and the second for simultaneous purification i.e. glycerol separation. Finally, purified biodiesel was produced with glycerol content below the detection limit.

Controlled drug release through regulated biodegradation of poly(lactic acid) using inorganic salts

Biodegradation rate of poly(lactic acid) (PLA) has been regulated, both increase and decrease with respect to the biodegradation of pure PLA, by embedding meager amount of inorganic salts in polymer matrix. Biodegradation is performed in enzyme medium on suspension and film and the extent of biodegradation is measured through spectroscopic technique which is also verified by weight loss measurement. Media pH has been controlled using trace amount of inorganic salt which eventually control the biodegradation of PLA. High performance liquid chromatography confirms the hydrolytic degradation of PLA to its monomer/oligomer. Induced pH by metal salts show maximum degradation at alkaline range (with calcium salt) while inhibition is observed in acidic medium (with iron salt). The pH of media changes the conformation of enzyme which in turn regulate the rate of biodegradation. Thermal degradation and increment of modulus indicate improvement in thermo-mechanical properties of PLA in presence of inorganic salts. Functional stability of enzyme with metal salts corresponding to acidic and alkaline pH has been established through a model to explain the conformational changes of the active sites of enzyme at varying pH influencing the rate of hydrolysis leading to regulated biodegradation of PLA. The tuned biodegradation has been applied for the controlled release of drug from the polymer matrix (both sustained and enhanced cumulative release as compared to pure polymer). The cell proliferation and adhesion are influenced by the acidic and basic nature of polymeric material tuned by two different inorganic salts showing better adhesion and proliferation in calcium based composite and, therefore, suggest biological use of these composites in biomedical applications.

Encapsulation of Pancreatic Lipase in Hydrogel Beads with Self-Regulating Internal pH Microenvironments: Retention of Lipase Activity after Exposure to Gastric Conditions

Oral delivery of lipase is important for individuals with exocrine pancreatic insufficiency; however, lipase loses activity when exposed to the highly acidic gastric environment. In this study, pancreatic lipase was encapsulated in hydrogel beads fabricated from alginate (gel former), calcium chloride (cross-linker), and magnesium hydroxide (buffer). Fluorescence confocal microscopy imaging was used to map the pH microclimate within the hydrogel beads under simulated gastrointestinal tract (GIT) conditions. The pH within buffer-free beads rapidly decreased when they moved from mouth (pH 6.3) to stomach (pH <4), leading to a loss of lipase activity in the small intestine. Conversely, the pH inside buffer-loaded beads remained close to neutral in the mouth (pH 7.33) and stomach (pH 7.39), leading to retention of lipase activity in the small intestine, as shown by pH-stat analysis of lipid digestion. The presence of the encapsulated buffer also reduced bead shrinkage under gastric conditions.

Ironing out their differences: dissecting the structural determinants of a phenylalanine aminomutase and ammonia lyase

Deciphering the structural features that functionally separate ammonia lyases from aminomutases is of interest because it may allow for the engineering of more efficient aminomutases for the synthesis of unnatural amino acids (e.g., β-amino acids). However, this has proved to be a major challenge that involves understanding the factors that influence their activity and regioselectivity differences. Herein, we report evidence of a structural determinant that dictates the activity differences between a phenylalanine ammonia lyase (PAL) and aminomutase (PAM). An inner loop region that closes the active sites of both PAM and PAL was mutated within PAM (PAM residues 77-97) in a stepwise approach to study the effects when the equivalent residue(s) found in the PAL loop were introduced into the PAM loop. Almost all of the single loop mutations triggered a lyase phenotype in PAM. Experimental and computational evidence suggest that the induced lyase features result from inner loop mobility enhancements, which are possibly caused by a 310-helix cluster, flanking α-helices, and hydrophobic interactions. These findings pinpoint the inner loop as a structural determinant of the lyase and mutase activities of PAM.

Organic co-solvents affect activity, stability and enantioselectivity of haloalkane dehalogenases

Haloalkane dehalogenases are microbial enzymes with a wide range of biotechnological applications, including biocatalysis. The use of organic co-solvents to solubilize their hydrophobic substrates is often necessary. In order to choose the most compatible co-solvent, the effects of 14 co-solvents on activity, stability and enantioselectivity of three model enzymes, DbjA, DhaA, and LinB, were evaluated. All co-solvents caused at high concentration loss of activity and conformational changes. The highest inactivation was induced by tetrahydrofuran, while more hydrophilic co-solvents, such as ethylene glycol and dimethyl sulfoxide, were better tolerated. The effects of co-solvents at low concentration were different for each enzyme-solvent pair. An increase in DbjA activity was induced by the majority of organic co-solvents tested, while activities of DhaA and LinB decreased at comparable concentrations of the same co-solvent. Moreover, a high increase of DbjA enantioselectivity was observed. Ethylene glycol and 1,4-dioxane were shown to have the most positive impact on the enantioselectivity. The favorable influence of these co-solvents on both activity and enantioselectivity makes DbjA suitable for biocatalytic applications. This study represents the first investigation of the effects of organic co-solvents on the biocatalytic performance of haloalkane dehalogenases and will pave the way for their broader use in industrial processes.

Crystal structure of Proteus mirabilis lipase, a novel lipase from the Proteus/psychrophilic subfamily of lipase family I.1

Bacterial lipases from family I.1 and I.2 catalyze the hydrolysis of triacylglycerol between 25-45°C and are used extensively as biocatalysts. The lipase from Proteus mirabilis belongs to the Proteus/psychrophilic subfamily of lipase family I.1 and is a promising catalyst for biodiesel production because it can tolerate high amounts of water in the reaction. Here we present the crystal structure of the Proteus mirabilis lipase, a member of the Proteus/psychrophilic subfamily of I.1lipases. The structure of the Proteus mirabilis lipase was solved in the absence and presence of a bound phosphonate inhibitor. Unexpectedly, both the apo and inhibitor bound forms of P. mirabilis lipase were found to be in a closed conformation. The structure reveals a unique oxyanion hole and a wide active site that is solvent accessible even in the closed conformation. A distinct mechanism for Ca²⁺ coordination may explain how these lipases can fold without specific chaperones.

Charge-surface correlation in electrospray ionization of folded and unfolded proteins

Electrospray-ionization mass spectrometry (ESI-MS) is widely used for protein studies. It has been shown that the extent of protein ionization under nondenaturing conditions correlates well with the solvent-accessible surface area of the tridimensional structure, for either folded monomers or multimeric complexes. The goal of this study was to test whether this relation holds for unfolded proteins as well. In order to overcome the paucity of structural data, the server ProtSA was used to model the conformational ensembles of proteins in the unfolded state and generate estimates of the average solvent accessibility. The results are analyzed along with literature data or original measurements by ESI-MS. It is found that the charge-to-surface relation holds for proteins in the unfolded state, free from solvent effects. A double-log plot is derived, in close agreement with published data for folded proteins. These results suggest that the solvent-accessible surface area is a key factor determining the extent of protein ionization by electrospray, independent of the conformational state. This conclusion helps rationalizing conformational effects in protein ESI-MS. The here reported relation can be used to predict the average solvent accessibility and, hence, the state of folding of unknown proteins from ESI-MS data.

Methods for detection and characterization of lipases: A comprehensive review

Microbial lipases are very prominent biocatalysts because of their ability to catalyze a wide variety of reactions in aqueous and non-aqueous media. The chemo-, regio- and enantio-specific behaviour of these enzymes has caused tremendous interest among scientists and industrialists. Lipases from a large number of bacterial, fungal and a few plant and animal sources have been purified to homogeneity. This article presents a critical review of different strategies which have been employed for the detection, purification and characterization of microbial lipases.