Enzyme, β-galactosidase immobilized on membrane surface for galacto-oligosaccharides formation from lactose: Kinetic study with feed flow under recirculation loop

A catalytic membrane approach as a way to obtain sweet and unsweet lactose-free milk

The growing need in the current market for innovative solutions to obtain lactose-free (L-F) milk is caused by the annual increase in the prevalence of lactose intolerance inside as well as the newborn, children, and adults. Various configurations of enzymes can yield two distinct L-F products: sweet (β-galactosidase) and unsweet (β-galactosidase and glucose oxidase) L-F milk. In addition, the reduction of sweetness through glucose decomposition should be performed in a one-pot mode with catalase to eliminate product inhibition caused by H2O2. Both L-F products enjoy popularity among a rapidly expanding group of consumers. Although enzyme immobilization techniques are well known in industrial processes, new carriers and economic strategies are still being searched. Polymeric carriers, due to the variety of functional groups and non-toxicity, are attractive propositions for individual and co-immobilization of food enzymes. In the presented work, two strategies (with free and immobilized enzymes; β-galactosidase NOLA, glucose oxidase from Aspergillus niger, and catalase from Serratia sp.) for obtaining sweet and unsweet L-F milk under low-temperature conditions were proposed. For free enzymes, achieving the critical assumption, lactose hydrolysis and glucose decomposition occurred after 1 and 4.3 h, respectively. The tested catalytic membranes were created on regenerated cellulose and polyamide. In both cases, the time required for lactose and glucose bioconversion was extended compared to free enzymes. However, these preparations could be reused for up to five (β-galactosidase) and ten cycles (glucose oxidase with catalase).

Functionalized electrospun nanofibers to enhance β-Galactosidase immobilization and catalytic activity for efficient galactooligosaccharide synthesis

This study aimed to immobilize β-galactosidase (β-GAL) into enhanced polystyrene (PS) electrospun nanofiber membranes (ENMs) with functionalized graphene oxide (GO). Initially, GO sheets were functionalized by salinization with 3-aminopropyl triethoxysilane (APTES). Then the ENMs (PS, PS/GO, and PS/GO-APTES) were prepared and characterized. Then, the β-GAL was immobilized in the different ENMs to produce the β-GAL-bound nanocomposites (PS-GAL, PS/GO-GAL, and PS/GO-APTES-GAL). Immobilization of β-GAL into PS/GO-APTES significantly improved enzyme adsorption by up to 87 %. Also, PS/GO-APTES-GAL improved the enzyme activity, where the highest enzyme activity was obtained at enzyme concentrations of 4 mg/L, 50 °C, and pH 4.5. Likewise, the storage stability and reusability of immobilized β-GAL were improved. Furthermore, this process led to enhanced catalytic behavior and transgalactosylation efficiency, where GOS synthesis (72 %) and lactose conversion (81 %) increased significantly compared to the free enzyme. Overall, the immobilized β-GAL produced in this study showed potential as an effective biocatalyst in the food industry.

Recent advances in β-galactosidase and fructosyltransferase immobilization technology

The highly demanding conditions of industrial processes may lower the stability and affect the activity of enzymes used as biocatalysts. Enzyme immobilization emerged as an approach to promote stabilization and easy removal of enzymes for their reusability. The aim of this review is to go through the principal immobilization strategies addressed to achieve optimal industrial processes with special care on those reported for two types of enzymes: β-galactosidases and fructosyltransferases. The main methods used to immobilize these two enzymes are adsorption, entrapment, covalent coupling and cross-linking or aggregation (no support is used), all of them having pros and cons. Regarding the support, it should be cost-effective, assure the reusability and an easy recovery of the enzyme, increasing its stability and durability. The discussion provided showed that the type of enzyme, its origin, its purity, together with the type of immobilization method and the support will affect the performance during the enzymatic synthesis. Enzymes' immobilization involves interdisciplinary knowledge including enzymology, nanotechnology, molecular dynamics, cellular physiology and process design. The increasing availability of facilities has opened a variety of possibilities to define strategies to optimize the activity and re-usability of β-galactosidases and fructosyltransferases, but there is still great place for innovative developments.

Identification and Immobilization of an Invertase With High Specific Activity and Sucrose Tolerance Ability of Gongronella sp. w5 for High Fructose Syrup Preparation

Invertases catalyze the hydrolysis of sucrose into fructose and glucose and can be employed as an alternative in producing high fructose syrup. In this study, we reported the heterologous expression of an invertase gene (GspInv) of Gongronella sp. w5 in Komagataella pastoris. GspInv activity reached 147.6 ± 0.4 U/mL after 5 days of methanol induction. GspInv is invertase with a high specific activity of 2,776.1 ± 124.2 U/mg toward sucrose. GspInv showed high tolerance to sucrose (IC 5 0 = 1.2 M), glucose (IC 5 0 > 2 M), fructose (IC 5 0 = 1.5 M), and a variety of metal ions that make it an ideal candidate for high fructose syrup production. A carbohydrate-binding module was sequence-optimized and fused to the N-terminus of GspInv. The fusion protein had the highest immobilization efficiency at room temperature within 1 h adsorption, with 1 g of cellulose absorption up to 8,000 U protein. The cellulose-immobilized fusion protein retained the unique properties of GspInv. When applied in high fructose syrup preparation by using 1 M sucrose as the substrate, the sucrose conversion efficiency of the fused protein remained at approximately 95% after 50 h of continuous hydrolysis on a packed bed reactor. The fused protein can also hydrolyze completely the sucrose in sugarcane molasses. Our results suggest that GspInv is an unusual invertase and a promising candidate for high fructose syrup preparation.

Highly efficient production of diverse rare ginsenosides using combinatorial biotechnology

The rare ginsenosides are recognized as the functionalized molecules after the oral administration of Panax ginseng and its products. The sources of rare ginsenosides are extremely limited because of low ginsenoside contents in wild plants, hindering their application in functional foods and drugs. We developed an effective combinatorial biotechnology approach including tissue culture, immobilization, and hydrolyzation methods. Rh2 and nine other rare ginsenosides were produced by methyl jasmonate-induced culture of adventitious roots in a 10 L bioreactor associated with enzymatic hydrolysis using six β-glycosidases and their combination with yields ranging from 5.54 to 32.66 mg L^-1 . The yield of Rh2 was furthermore increased by 7% by using immobilized BglPm and Bgp1 in optimized pH and temperature conditions, with the highest yield reaching 51.17 mg L^-1 (17.06% of protopanaxadiol-type ginsenosides mixture). Our combinatorial biotechnology method provides a highly efficient approach to acquiring diverse rare ginsenosides, replacing direct extraction from Panax plants, and can also be used to supplement yeast cell factories.

Sustainable bioconversion of food waste into high-value products by immobilized enzymes to meet bio-economy challenges and opportunities - A review

Over the past few years, food waste has intensified much attention from the local public, national and international organizations as well as a wider household territory due to increasing environmental, social and economic concerns, climate change and scarcity of fossil fuel resources. On one aspect, food-processing waste represents a substantial ecological burden. On the other hand, these waste streams are rich in carbohydrates, proteins, and lipids, thus hold significant potential for biotransformation into an array of high-value compounds. Indeed, the high sugar, protein, and fat content render food waste streams as attractive feedstocks for enzymatic valorization given the plentiful volumes generated annually. Enzymes as industrial biocatalysts offer unique advantages over traditional chemical processes with regard to eco-sustainability, and process efficiency. Herein, an effort has been made to delineate immobilized enzyme-driven valorization of food waste streams into marketable products such as biofuels, bioactive compounds, biodegradable plastics, prebiotics, sweeteners, rare sugars, surfactants, etc. Current challenges and prospects are also highlighted with respect to the development of industrially adaptable biocatalytic systems to achieve the ultimate objectives of sustainable manufacturing combined with minimum waste generation. Applications-based strategies to enzyme immobilization are imperative to design cost-efficient and sustainable industrially applicable biocatalysts. With a deeper apprehension of support material influences, and analyzing the extreme environment, enzymes might have significant potential in improving the overall sustainability of food processing.

Simple and Mediator-Free Urea Sensing Based on Engineered Nanodiamonds with Polyaniline Nanofibers Synthesized in Situ

In an effort to develop a simple and mediator-free sensing media for urea, a polyaniline (PANI) and graphitized nanodiamond (GND) nanocomposite was prepared at room temperature via an in situ interfacial polymerization approach. The interaction of ions produced during the hydrolysis of urea with nanomaterial was utilized for the amperometric sensing of urea. The performance of this composite (GND/PANI) was evaluated for the detection of urea referenced to PANI. Accordingly, both platforms exhibited good linearity across a varying concentration of 0.1 to 0.9 mg mL^-1 with limit of detection (LOD) values of 0.07 (PANI) and 0.05 mg mL^-1 (GNDs-PANI). As such, both of them were able to detect urea well below the common range in real samples. Moreover, their sensitivities were also determined as 140.5 and 381.5 μA (mg mL^-1)^-1 cm^-2 with a response time of 15 and 20 s, respectively. As such, the incorporation of GND with PANI was helpful toward enhancement of sensitivity.

Kinetics and model development for enzymatic synthesis of fructo-oligosaccharides using fructosyltransferase

Experimental investigations were made to synthesize fructo-oligosaccharides (FOS) from sucrose using fructosyltransferase. The influence of various parameters such as temperature (45-55 °C), pH (4-5), initial sucrose concentration (ISC: 300-500 g/L) and enzyme concentration (4-32 U/mL) were varied. A maximum FOS yield of 60% was observed at ISC 500 g/L, pH 4.5 with enzyme activity 32 U/mL and at 55 °C. It was confirmed that 1-kestose (tri-) was the major product of FOS as compared to nystose (tetra-) and fructosylnystose (penta-saccharides). Further, the reaction rate increases with increase in temperature. From separate sets of experiments, it was observed that FOS formation was affected by glucose inhibition. Apart from the increase in the rate of FOS formation with increasing enzyme activity, the final values of FOS yield increase though till 16 U/mL and thereafter attain plateau. A kinetic model was also developed, based on Michaelis-Menten kinetics, and a five-step ten-parameter model, including glucose inhibition, was obtained. Model was solved using COPASI(®) (version 4.8) solver for kinetic parameter estimations followed by time course simulations.