Process intensification: The future for enzymatic processes?

Paper-based ligand fishing method for rapid screening and real-time capturing of α-glucosidase inhibitors from the Chinese herbs

Identifying medicinally relevant compounds from natural resources generally involves the tedious work of screening plants for the desired activity before capturing the bioactive molecules from them. In this work, we created a paper-based ligand fishing platform to vastly simplify the discovery process. This paper-based method exploits the enzymatic cascade reaction between α-glucosidase (GAA), glucose oxidase (GOx), and horseradish peroxidase (HRP), to simultaneously screen the plants and capture the GAA inhibitors from them. The designed test strip could capture ligands in tandem with screening the plants, and it features a very simply operation based on direct visual assessment. Multiple acylated flavonol glycosides from the leaves of Quercus variabilis Blume were newly found to possess GAA inhibitory activities, and they may be potential leads for new antidiabetic medications. Our study demonstrates the prospect of the newly discovered GAA ligands as potential bioactive ingredients as well as the utility of the paper-based ligand fishing method.

Sustainable biorefinery approach by utilizing xylose fraction of lignocellulosic biomass

Lignocellulosic biomass (LCB) has been a lucrative feedstock for developing biochemical products due to its rich organic content, low carbon footprint and abundant accessibility. The recalcitrant nature of this feedstock is a foremost bottleneck. It needs suitable pretreatment techniques to achieve a high yield of sugar fractions such as glucose and xylose with low inhibitory components. Cellulosic sugars are commonly used for the bio-manufacturing process, and the xylose sugar, which is predominant in the hemicellulosic fraction, is rejected as most cell factories lack the five‑carbon metabolic pathways. In the present review, more emphasis was placed on the efficient pretreatment techniques developed for disintegrating LCB and enhancing xylose sugars. Further, the transformation of the xylose to value-added products through chemo-catalytic routes was highlighted. In addition, the review also recapitulates the sustainable production of biochemicals by native xylose assimilating microbes and engineering the metabolic pathway to ameliorate biomanufacturing using xylose as the sole carbon source. Overall, this review will give an edge on the bioprocessing of microbial metabolism for the efficient utilization of xylose in the LCB.

Review of osmotic dehydration: Promising technologies for enhancing products' attributes, opportunities, and challenges for the food industries

Osmotic dehydration (OD) is an efficient preservation technology in that water is removed by immersing the food in a solution with a higher concentration of solutes. The application of OD in food processing offers more benefits than conventional drying technologies. Notably, OD can effectively remove a significant amount of water without a phase change, which reduces the energy demand associated with latent heat and high temperatures. A specific feature of OD is its ability to introduce solutes from the hypertonic solution into the food matrix, thereby influencing the attributes of the final product. This review comprehensively discusses the fundamental principles governing OD, emphasizing the role of chemical potential differences as the driving force behind the molecular diffusion occurring between the food and the osmotic solution. The kinetics of OD are described using mathematical models and the Biot number. The critical factors essential for optimizing OD efficiency are discussed, including product characteristics, osmotic solution properties, and process conditions. In addition, several promising technologies are introduced to enhance OD performance, such as coating, skin treatments, freeze-thawing, ultrasound, high hydrostatic pressure, centrifugation, and pulsed electric field. Reusing osmotic solutions to produce innovative products offers an opportunity to reduce food wastes. This review explores the prospects of valorizing food wastes from various food industries when formulating osmotic solutions for enhancing the quality and nutritional value of osmotically dehydrated foods while mitigating environmental impacts.

Conjugation of soymilk protein and arabinoxylan induced by peroxidase to improve the gel properties of tofu

Arabinoxylan (AX) can form stable covalent bonds with protein to improve gel properties. We aimed to prepare a conjugate between soymilk protein (SMP) and AX by peroxidase, followed by the addition of transglutaminase (TG) to prepare tofu gels. The conjugate's properties and their effects on the mechanical properties, rheological properties, and microstructure of tofu gels were evaluated. Results revealed that the α-helix content decreased, the β-sheet content increased, and the surface hydrophobicity reduced from 1.60 × 105 to 1.27 × 105. The optimal amount of AX required to improve the properties of tofu gel was 1.0%. The tofu gel showed better hardness (118.44 g), water holding capacity (WHC) (86.17%), and higher storage modulus (G') and loss modulus (G″). Low-Field NMR (LF-NMR) showed that the water was evenly distributed. Scanning electron microscopy (SEM) revealed a denser and more regular three-dimensional gel network.

Integrating Biocatalysis with Viscous Deep Eutectic Solvents in Lab-On-A-Chip Microreactors

The combination of deep eutectic solvents (DESs, ChCl/glycerol 1 : 2) with buffer (up to 15 % v/v) leads to solvent mixtures that exert viscosities below 25 mPa s^-1 at 45 °C while keeping their non-aqueous nature. This enables the setup of efficient enzymatic esterifications, which can also be applied in different continuous systems. Following those premises, the use of microreactors in biocatalytic reactions was explored using (low-viscous) DES-buffer media, showing that reactions could be performed efficiently. Under non-optimized conditions, the microreactor devices led to specific productivities considerably higher than those observed in the batch reactor (14 vs. 0.24 mg_product  min^-1  mg_biocat ^-1 ) at the same enzyme loadings and conversion of 6 % (to assure a fair comparison). Looking beyond, the combination of several microchannels (e. g., in scale-out fashion) with DES-water media may lead to powerful, sustainable, and efficient tools for industrial synthesis.

Alternative methods for cleaning membranes in water and wastewater treatment

Membrane fouling is caused by foulant deposition or adsorption through physical or chemical interactions on the membrane surface, causing the reduction of flux through the membrane. The main drawbacks of chemical agents used for cleaning are cost, damage caused on the membrane, and waste stream making the process unattractive. Alternative, methods such as ultrasound, enzymatic process, and osmotic backwashing were explored for membrane cleaning. Among all mentioned methods, micronanobubbles have been reported as a promising and emergent method for membrane surface cleaning; unfortunately, the information is limited, but preliminary studies have shown it as an efficient, cheap, and environmentally friendly technique. Other methods like electrically and vibratory-enhanced membrane cleaning also could be interesting but currently are unexplored and information is limited. PRACTITIONER POINTS: Chemical cleaning is an efficient option; however, from an environmental point of view, it is not attractive, and high concentrations could cause damage to the membrane. Micronanobubbles are an emergent and suitable technology for membrane and surface cleaning. Membrane modification and functionalization avoid membrane fast fouling, and the cleaning process is easier, but the manufacture cost could be expensive.

Highly effective enzymes immobilization on ceramics: Requirements for supports and enzymes

Enzyme immobilization is a well-known method for the improvement of enzyme reusability and stability. To achieve very high effectiveness of the enzyme immobilization, not only does the method of attachment need to be optimized, but the appropriate support must be chosen. The essential necessities addressed to the support applied for enzyme immobilization can be focused on the material features as well as on the stability and resistances in certain conditions. Ceramic membranes and nanoparticles are the most widespread supports for enzyme immobilization. Hence, the immobilization of enzymes on ceramic membrane and nanoparticles are summarized and discussed. The important properties of the supports are particle size, pore structure, active surface area, volume to surface ratio, type and number of reactive available groups, as well as thermal, mechanical, and chemical stability. The modifiers and the crosslinkers are crucial to the enzyme loading amount, the chemical and physical stability, and the reusability and catalytical activity of the immobilized enzymes. Therefore, the chemical and physical methods of modification of ceramic materials are presented. The most popular and used modifiers (e.g. APTES, CPTES, VTES) as well as activating agents (GA, gelatin, EDC and/or NHS) applied to the grafting process are discussed. Moreover, functional groups of enzymes are presented and discussed since they play important roles in the enzyme immobilization via covalent bonding. The enhanced physical, chemical, and catalytical properties of immobilized enzymes are discussed revealing the positive balance between the effectiveness of the immobilization process, preservation of high enzyme activity, its good stability, and relatively low cost.

Fusion of maltooligosaccharide-forming amylases from two origins for the improvement of maltopentaose synthesis

Maltopentaose-forming amylases are promising enzymes for their ability to hydrolyze starch and produce functional maltooligosaccharides. Two maltopentaose-forming amylase genes from Bacillus megaterium (BmMFA) and Saccharophagus degradans (SdMFA) were expressed heterologously and their characteristics were analyzed. BmMFA has substantial thermostability and SdMFA owns superior product specificity. The carbohydrate-binding module of SdMFA was fused with BmMFA and the fused protein showed ideal enzymatic properties and displayed potential for industrial production of maltopentaose. Under the optimized conditions, the final product containing 47.41% maltopentaose was obtained with a conversion rate of 92.67% from starch. This study provides a novel strategy for the directed modification of MFAses through protein fusion approach.

Implementation of an Enzyme Membrane Reactor to Intensify the α-O-Glycosylation of Resveratrol Using Cyclodextrins

The O-glycosylation of resveratrol increases both its solubility in water and its bioavailability while preventing its oxidation, allowing a more efficient use of this molecule as a bioactive ingredient in pharmaceutical and cosmetic applications. Resveratrol O-glycosides can be obtained by enzymatic reactions. Recent developments have made it possible to selectively obtain resveratrol α-glycosides from the β-cyclodextrin–resveratrol complex in water with a yield of 35%. However, this yield is limited by the partial hydrolysis of the resveratrol glycosides produced during the reaction. In this study, we propose to intensify this enzymatic reaction by coupling the enzymatic reactor to a membrane process. Firstly, membrane screening was carried out at the laboratory scale and led to the choice of a GE polymeric membrane with a cut-off of 1 kDa. This membrane allowed the retention of 65% of the β-cyclodextrin–resveratrol complex in the reaction medium and the transfer of 70% of the resveratrol α-O-glycosides in the permeate. In a second step, this membrane was used in an enzymatic membrane reactor and improved the yield of the enzymatic glycosylation up to 50%.

Latest Developments in Membrane (Bio)Reactors

The integration of membranes inside a catalytic reactor is an intensification strategy to combine separation and reaction steps in one single physical unit. In this case, a selective removal or addition of a reactant or product will occur, which can circumvent thermodynamic equilibrium and drive the system performance towards a higher product selectivity. In the case of an inorganic membrane reactor, a membrane separation is coupled with a reaction system (e.g., steam reforming, autothermal reforming, etc.), while in a membrane bioreactor a biological treatment is combined with a separation through the membranes. The objective of this article is to review the latest developments in membrane reactors in both inorganic and membrane bioreactors, followed by a report on new trends, applications, and future perspectives.

Continuous Production of Galacto-Oligosaccharides by an Enzyme Membrane Reactor Utilizing Free Enzymes

Galacto-oligosaccharides (GOS) are prebiotic compounds widely used for their health-promoting effects. Conventionally, GOS is produced by the enzymatic conversion of lactose in stirred tank reactors (STR). The high operational costs associated with enzyme inactivation and removal might be reduced by the application of enzyme membrane reactors (EMR). In this study, we aimed to assess the potential of continuous GOS production by EMR using soluble Biolacta N5, a Bacillus circulans-derived commercial enzyme preparation. The steady-state performance of the EMR equipped with an ultrafiltration module was investigated as function of residence time (1.1-2.8 h) and enzyme load (17-190 U·g^-1) under fixed operational settings of temperature (50 °C), pH (6.0), lactose feed concentration (300 g·kg^-1), and recirculation flow-rate (0.18 m³·h^-1). Results indicate that the yield of oligosaccharides with higher degree of polymerization (DP3-6) in STR (approx. 38% on total carbohydrate basis) exceeds that measured in EMR (ranging from 24% to 33%). However, a stable catalytic performance without a significant deterioration in product quality was observed when operating the EMR for an extended period of time (> 120 h). Approx. 1.4 kg of DP3-6 was produced per one gram of crude enzyme preparation over the long-term campaigns, indicating that EMR efficiently recovers enzyme activity.

Sucrose fatty acid esters: synthesis, emulsifying capacities, biological activities and structure-property profiles

The notable physical and chemical properties of sucrose fatty acid esters have prompted their use in the chemical industry, especially as surfactants, since 1939. Recently, their now well-recognized value as nutraceuticals and as additives in cosmetics has significantly increased demand for ready access to them. As such a review of current methods for the preparation of sucrose fatty acid esters by both chemical and enzymatic means is warranted and is presented here together with an account of the historical development of these compounds as surfactants (emulsifiers). The somewhat belated recognition of the antimicrobial, anticancer and insecticidal activities of sucrose esters is also discussed along with a commentary on their structure-property profiles.

Extending Designed Linear Biocatalytic Cascades for Organic Synthesis

Artificial cascade reactions involving biocatalysts have demonstrated a tremendous potential during the recent years. This review just focuses on selected examples of the last year and putting them into context to a previously published suggestion for classification. Subdividing the cascades according to the number of catalysts in the linear sequence, and classifying whether the steps are performed simultaneous or in a sequential fashion as well as whether the reaction sequence is performed in vitro or in vivo allows to organise the concepts. The last year showed, that combinations of in vivo as well as in vitro are possible. Incompatible reaction steps may be run in a sequential fashion or by compartmentalisation of the incompatible steps either by using special reactors (membrane), polymersomes or flow techniques.