Fig 2 - uploaded by Dr-Arafat Tanash
Content may be subject to copyright.
Source publication
Aspergillus subolivaceus dextranase is immobilized on several carriers by entrapment and covalent binding with cross-linking. Dextranase immobilized on BSA with a cross-linking agent shows the highest activity and considerable immobilization yield (66.7%). The optimum pH of the immobilized enzyme is shifted to pH 6.0 as compared with the free enzym...
Citations
... Dextranases are widely used for different purposes, in medicine for hydrolysis of native dextran produced by Leuconostoc mesenteroides in the manufacturing of blood substitutes, as well as in the prevention of dental caries (Abdel-Naby et al. 1999;Khalikova et al. 2003;Š melcerović et al. 2008). Also, other dextranolytic enzymes are used in the synthesis of potentially valuable prebiotic oligosaccharides that have an important role in the formulation of the drug and cosmetic products, vaccines as well as in food industry (El-Tanah et al. 2011). In addition, dextranases have significant applications in the cosmetic, food and detergent industries, but one of the major industrial applications is in the sugar industry for removing difficult mucous residues (Hild et al. 2007; Khalikova et al. 2003). ...
With the aid of experimental design, in this study, we have investigated the activity and stability of dextranase, an important extracellular inducible enzyme that specifically hydrolyzes the α-1,6 glycosidic linkages of dextran, leading to the formation of D-glucose and shorter oligosaccharides. The experimental design results showed the significant individual as well as interaction effects of the tested parameters affecting the dextranase activity and stability. The numerical optimization study suggested that the desired maximum activity and stability of dextranase can be obtained at temperature 40 °C and pH value 6.5. In addition, stability tests showed that dextranase was stable, without compromising its activity, up to 55 °C and in pH range 5–8. Considering the influence of investigated reagents on dextranase activity, the results revealed a pronounced activating effect of glycerol and sucrose, especially with increasing their concentration, with the highest activity detected in the presence of sucrose at 10 mM (129%). Regarding the influence of added metal ions, the higher dextranase activity is recorded in the presence of Ag+, Ca2+, K+, Mg2+, and Si2+ ions, from which the Ca2+ ions were the most effective, and in their presence, at 10 mM the activity of dextranase was 119%.
... Moreover, there are also other bacteria (Bacteroides, Streptococcus, Pseudomonas and Thermoanaerobacter [38,66,85,148]), fungi (Paecilomyces lilacinus and species of the genus Penicillium, Chaetomium and Aspergillus [36,37,85,143] and few yeasts which cause activation of such enzymes due to which sucrose gets degraded or deteriorated. Furthermore, various issues arise during sugar processing as a result of dextran generation, such as filtration, clarifying, crystal shape alteration, crystallization, viscosity reduction, and so on [22,59]. ...
Sugarcane deteriorates at a quick rate, just like other perishable crops. The quick loss of sucrose content in sugarcane from the time it is harvested has a significant impact on sugar recovery. This problem of post-harvest sucrose losses in sugarcane is a serious concern in cane-producing countries, as it not only leads to low sugar recovery in mills, but also to poor sugar refining. Unreasonable delays in cane transportation from the fields to the mill are frequently linked to a number of problems related to primary or secondary sucrose losses, all of which contribute to a significant reduction in cane weight and sugar recovery. In sugar mills, the processing of damaged or stale canes also presents a number of challenges, including increased viscosity due to dextran generation, formation of acetic acid, and dextrans due to Leuconostoc spp. invasion, and so on. The combination of all of these variables results in low sugar quality, resulting in significant losses for sugar mills. The primary and secondary losses caused by post-harvest sucrose degradation in sugarcane are enlisted. The employment of physico-chemical technologies in farmers' fields and sugar mills to control and minimize these losses has also been demonstrated.
... Similar K m values indicate similar affinity between substrates and the non-cross-linked dextranase and GA-cross-linked dextranase. Similar V max and K m change of the immobilized dextranase are found in research from El-Tanash et al. (2011). However, the Michaelis-Menten parameters only describe the reaction velocity of the enzyme at the beginning of the hydrolysis reaction (Ivanauskas et al., 2016;Johnson & Goody, 2011). ...
... However, the scenario around the CLEAs above the PDA coating layer might be different. The crosslinking led to high enzyme concentration in the CLEAs, and static compaction occurred among the enzymes, so there might be very limited space for whole dextran substrate to diffuse into the active sites for endohydrolysis (El-Tanash et al., 2011;. Instead, the limited space might only allow the terminal side of the large molecules to penetrate the CLEAs, leading to an exo-hydrolysis. ...
An enzymatic membrane reactor (EMR) with immobilized dextranase provides an excellent opportunity for tailoring the molecular weight (Mw) of oligodextran to significantly improve product quality. However, a highly efficient EMR for oligodextran production is still lacking and the effect of enzyme immobilization strategy on dextranase hydrolysis behavior has not been studied yet. In this work, a functional layer of polydopamine (PDA) or nanoparticles made of tannic acid (TA) and hydrolysable 3-amino-propyltriethoxysilane (APTES) was first coated on commercial membranes. Then cross-linked dextranase or non-cross-linked dextranase was loaded onto the modified membranes using incubation mode or fouling-induced mode. The fouling-induced mode was a promising enzyme immobilization strategy on the membrane surface due to its higher enzyme loading and activity. Moreover, unlike the non-cross-linked dextranase that exhibited a normal endo-hydrolysis pattern, we surprisingly found that the cross-linked dextranase loaded on the PDA modified surface exerted an exo-hydrolysis pattern, possibly due to mass transfer limitations. Such alteration of hydrolysis pattern has rarely been reported before. Based on the hydrolysis behavior of the immobilized dextranase in different EMRs, we propose potential applications for the oligodextran products. This study presents a unique perspective on the relation between the enzyme immobilization process and the immobilized enzyme hydrolysis behavior, and thus opens up a variety of possibilities for the design of a high-performance EMR.
... Table 5 reports on the effect of different metal ions on enzyme activity before and after immobilization. For example, the effects of metal ions have been investigated on dextranase (isolated from Aspergillus subolivaceus) immobilized by cross-linking on bovine serum albumin (BSA) [83]. Soluble and immobilized dextranase were incubated in the presence of different metal ions at room temperature for 30 min. ...
... Notably, K + , Mg 2+ and Ca 2+ had negligible effects on both the two enzyme forms, while Hg 2+ completely inhibited their activity, plausibly binding to the thiols group of cysteine residues of the enzyme. Interestingly, although Pb 2+ , Cu 2+ and Al 3+ cations are known to interact with cysteine [84], immobilized dextranase was more resistant to these ions than the soluble enzyme [83]. In another study, cyclodextrin glucono-transferase (CGTase) isolated from Bacillus macerans was immobilized on sodium alginate beads and its activity was tested in the presence of various metal ions [85]. ...
A variety of organic nanomaterials and organic polymers are used for enzyme immobilization to increase enzymes stability and reusability. In this study, the effects of the immobilization of enzymes on organic and organic-inorganic hybrid nano-supports are compare. Immobilization of enzymes on organic support nanomaterials was reported to significantly improve thermal, pH and storage stability, acting also as a protection against metal ions inhibitory effects. In particular, the effects of enzyme immobilization on reusability, physical, kinetic and thermodynamic parameters were considered. Due to their biocompatibility with low health risks, organic support nanomaterials represent a good choice for the immobilization of enzymes. Organic nanomaterials, and especially organic-inorganic hybrids, can significantly improve the kinetic and thermodynamic parameters of immobilized enzymes compared to macroscopic supports. Moreover, organic nanomaterials are more environment friendly for medical applications, such as prodrug carriers and biosensors. Overall, organic hybrid nanomaterials are receiving increasing attention as novel nano-supports for enzyme immobilization and will be used extensively.
... Presently, most strains reported to produce dextranase include molds, bacteria, and yeast, such as Chaetomium, 10 Penicillium, 9,16,17 Aspergillus subolivaceus, 18 Sporothrix schenckii, 19 Bacillus sp., 13 Lipomyces starkeyi, 20 and L. starkeyi NCYC1436. 21 Dextranases produced by molds have a longer fermentation time and higher energy consumption when compared with bacteria. ...
Oligosaccharides have important alimental and medical applications. Dextranase has been used to produce isomalto-oligosaccharides (IMOs). In this study, we isolated dextranase-producing bacteria from sugarcane-cultivated soil. Identification of the isolate based on its phenotypical, physiological, and biochemical characteristics, as well as 16S ribosomal deoxyribonucleic acid gene sequencing yielded Shewanella sp. strain GZ-7. The molecular weight of the dextranase produced by this strain was 100-135 kDa. The optimum temperature and pH for dextranase production were 40 °C and 7.5, respectively. The enzyme was found to be stable at the pH range of 6.0-8.0 and the temperature range of 20 °C-40 °C. Thin-layer chromatography and high-performance liquid chromatography of the enzymolysis products of the substrate confirmed the enzyme to be endodextranase. Under the optimal conditions, the ratio of IMOs could reach 91.8% of the hydrolyzate. The final products were found to efficiently scavenge the 2,2-diphenyl-1-picrylhydrazyl, hydroxyl, and superoxide anion radicals. In general, dextranase and hydrolyzates have high potential prospects for application in the future.
... [140]. The optimum pH can slightly shift when enzymes are immobilized, particularly due to the change in the ionic environment around the active site [141,142]. Though there is no certain rule predicting the pH shift tendency, immobilized glycosidase enzymes with a broader optimum pH offer greater advantages for industrial applications, as the versatility increases [143]. ...
Certain types of oligosaccharides are especially interesting due to their high commercial value, however, the traditional oligosaccharide fabrication process is neither sustainable nor tailorable for obtainment of commercial standard oligosaccharide streams. The use of enzymatic membrane reactors (EMR) is proposed as a sustainable strategy to obtain oligosaccharides through a coupled bioreaction-separation process. In such process, glycosidic enzymes function as catalysts and membranes as selective barriers tailoring the molecular weight of products.
Most of previous studies on oligosaccharides production by EMR have focused either on optimal operation of the enzyme reaction or the membrane filtration separately, but none of them have considered the implications of coupling both steps together. It is therefore the aim of this review to critically assess the available literature on the topic from a novel point of view: by paying special attention to the interactions between enzyme reaction-membrane filtration, which are critical for the performance of the overall process. Depending on the reaction conditions, the generated fouling directly affecting filtration performance varies. Such fouling depends on the membrane type and operation mode, which will in turn have an influence on the enzyme performance. The proposed review aims at providing a critical overview of the variables influencing performance and will provide tips for optimal configuration and operation of the coupled system.
... The activity and K m were measured for dextransucrase, and dextranase, in their free and immobilized forms ( Table 1). The values for enzymes activity and K m for both the enzymes were in a similar range of previous reports [22,23]. A slight decrease in the enzymes activity and modest enhancement in K m were experienced after enzyme entrapment in alginate-pectin beads. ...
The genes for dextransucrase and dextranase were cloned from the genomic regions of Leuconostoc mesenteroides MTCC 10508 and Streptococcus mutans MTCC 497, respectively. Heterologous expression of genes was performed in Escherichia coli. The purified enzyme fractions were entrapped in the alginate–pectin beads. A high immobilization yield of dextransucrase (~ 96%), and dextranase (~ 85%) was achieved. Alginate–pectin immobilization did not affect the optimum temperature and pH of the enzymes; rather, the thermal tolerance and storage stability of the enzymes was improved. The repetitive batch experiments suggested substantially good operational stability of the co-immobilized enzyme system. The synergistic catalytic reactions of alginate–pectin co-entrapped enzyme system were able to produce 7–10 g L⁻¹ oligosaccharides of a high degree of polymerization (DP 3–9) from sucrose (~ 20 g L⁻¹) containing feedstocks, e.g., table sugar and cane molasses. The alginate–pectin-based co-immobilized enzyme system is a useful catalytic tool to bioprocess the agro-industrial bio-resource for the production of prebiotic biomolecules.
... On an industrial scale, fermentation time is a vital factor as it governs the cost of the final product. One of the major drawback of fungal (4 to 5 days) or yeast (84 h) dextranase production is the prolong fermentation time period (El-Tanash et al. 2011;Koenig and Day 1989;Wu et al. 2011). Therefore, to overcome this problem B. megaterium KIBGE-IB31 was subjected to fermentation for different time intervals to attain a high yield of dextranase. ...
Bacillus megaterium KIBGE-IB31 was isolated from a hydrothermal spring that is proficient in the hyper-production of extracellular dextranase. The distinctive features of this strain include its aer-obic and thermophilic nature. The data regarding thermophilic organisms which are capable of producing dextranase is sparse, therefore, the geothermal springs were explored with the purpose to isolate a bacterium capable of hydrolyzing dextran. Strain characterization was based on the phenotypic and genotypic analysis. The thermophile produced dextranase under specific fermentation conditions. Micro and macronutrients were tested while exploring the fermentation parameters for maximum enzyme titers. Maximum production of 464.68 U/ml with a specific activity of 160.2 U/mg was achieved when 10.0 kDa dextran (15.0 g/l) was amalgamated with various trace elements and nitrogen sources at 60 C up to 24 h of fermentation time. Inoculum size and agitation speed also had a positive impact on maximum enzyme yield. Hydrolytic action of dextranase was observed by studying the surface topology of dextran through scanning electron microscopy. The results indicate that the dextranase synthesized by this thermophile can be used for the hydrolysis of the biopolymer. ARTICLE HISTORY
... However, the V max value of dextranase decreased after entrapment into the spheres with a calculated value of 4732 μmol ml -1 with a standard error of 90.34, and the K m value of entrapped dextranase varied from the value of its soluble counterpart with a twofold increase of 9.466 mg ml -1 having a standard error of 0.654. The same phenomenon after immobilization was also reported by El-Tanash, and the reason suggested for the increased K m value was the low availability of the substrate for the active site of immobilized dextranase while a decrease in velocity of reaction represented a decrease in flexibility of dextranase after entrapment [26]. Previously, it was also reported by another author that entrapment did not cause a pronounced effect on the kinetic characteristics of the enzyme [27]. ...
Alginate is an inexpensive, nontoxic, valuable biopolymer utilized in the study for the immobilization of commercially applicable biocatalyst dextranase. Dextranase was immobilized by an entrapment method, and alginate hydrogel spheres were synthesized after optimizing several parameters. A sodium alginate concentration of 4.0% was noticed to be suitable along with a calcium chloride concentration of 0.2 molar after providing a curing time of 20 minutes. After comparing the characteristics of the entrapped enzyme with those of the soluble one, it was observed that the characteristics were more or less the same except for the change in reaction time which was noticed to be prolonged in the case of entrapped dextranase while the change in temperature and pH optima was not observed. The variation in Vmax and Km values of dextranase after entrapment was also noted. However, after extensive stability examination studies, it was found that dextranase became more stable after entrapment; as a result, it retained more than 50% of its original activity at elevated temperature even after exposure for about 2.0 hours. The reusability of dextranase was up to 7.0 cycles after performing catalytic activity under constant condition.
... Dextranases are produced by different microorganisms, including bacteria [2e4], yeasts [5] and filamentous fungi [1,6,7]. These enzymes are of practical interest due to their ability to produce isomaltooligosaccharides (IMO) belonging to the group of prebiotic functional products [8]. ...
The dexA gene encoding Penicillium funiculosum dextranase (GenBank accession MH581385) belonging to family 49 of glycoside hydrolases (GH49) was cloned and heterologously expressed in two recipient strains, P. canescens RN3-11-7 and P. verruculosum B1-537. Crude enzyme preparations with the recombinant dextranase content of 8–36% of the total secreted protein were obtained on the basis of new Penicillium strains. Both recombinant forms of the dextranase were isolated in a homogeneous state using chromatographic techniques. The purified enzymes displayed very similar properties, that is, pI 4.55, activity optima at pH 4.5–5.0 and 55–60 °C and a melting temperature of 60.7–60.9 °C. They were characterized by similar specific activities (1020–1340 U/mg) against dextrans with a mean molecular mass of 20, 70 and 500 kDa, as well as similar kinetic parameters in the hydrolysis of 70 kDa dextran (Km = 1.10–1.11 g/L, kcat = 640–680 s⁻¹). However, the recombinant dextranases expressed in P. canescens and P. verruculosum had different molecular masses according to the data of SDS-PAGE (∼63 and ∼60 kDa, respectively); this was the result of different N-glycosylation patterns as MALDI-TOF mass spectrometry analysis showed. The main products of dextran hydrolysis at its initial phase were isomaltooligosaccharides, while after the prolonged time (24 h) the reaction system contained isomaltose and glucose as the major products and minor amounts of other oligosaccharides.
