Production of prebiotic enriched maple syrup through enzymatic conversion of sucrose into fructo-oligosaccharides

Maple syrup, a popular natural sweetener has a high content of sucrose, whose consumption is linked to different health issues such as obesity and diabetes. Hence, within this paper, the conversion of sucrose to prebiotics (fructo-oligosaccharides, FOS) was proposed as a promising approach to obtaining a healthier, value-added product. Enzymatic conversion was optimized with respect to key experimental factors, and thereafter derived immobilized preparation of fructosyltransferase (FTase) from Pectinex® Ultra SP-L (FTase-epoxy Purolite, 255 IU/g support) was successfully utilized to produce novel functional product in ten consecutive reaction cycles. The product, obtained under optimal conditions (60 °C, 7.65 IU/mL, 12 h), resulted in 56.0% FOS, 16.7% sucrose, and 27.3% monosaccharides of total carbohydrates, leading to a 1.6-fold reduction in caloric content. The obtained products` prebiotic potential toward the probiotic strain Lactobacillus plantarum 299v was demonstrated. The changes in physico-chemical and sensorial characteristics were esteemed as negligible.

Prebiotic levan type fructan from Bacillus subtilis PR-C18 as a potent antibiofilm agent: Structural elucidation and in silico analysis

The global demand for therapeutic prebiotics persuades the quest for novel exopolysaccharides that can retard the growth of pathobionts and healthcare-associated pathogens. In this regard, an exopolysaccharide (3.69 mg/mL) producing strain showing prebiotic and antibiofilm activity was isolated from indigenous pineapple pomace of Tripura and identified as Bacillus subtilis PR-C18. Zymogram analysis revealed EPS PR-C18 was synthesized by levansucrase (∼57 kDa) with a maximal activity of 4.62 U/mg. Chromatography techniques, FTIR, and NMR spectral data revealed the homopolymeric nature of purified EPS with a molecular weight of 3.40 × 104 Da. SEM and rheological study unveiled its microporous structure and shear-thinning effect. Furthermore, EPS PR-C18 showed remarkable emulsification, flocculation, water retention, water solubilization, and antioxidant activity. DSC-TGA data demonstrated its high thermostability and cytotoxicity analysis verified its nontoxic biocompatible nature. In addition, the antibiofilm activity of EPS PR-C18 was validated using molecular docking, molecular simulation, MM-GBSA and PCA studies, which exhibited its strong binding affinity (-20.79 kcal/moL) with PelD, a virulence factor from Pseudomonas aeruginosa. Together, these findings support the future exploitation of EPS PR-C18 as an additive or adjuvant in food and pharmaceutical sectors.

Insights into the heterogeneity of levan polymers synthesized by levansucrase Bs-SacB from Bacillus subtilis 168

Levan is an enzymatically synthesized fructose polymer with widely reported structural heterogeneity depending on the producing levansucrase, the reaction conditions employed for its synthesis and the characterization techniques. We studied here the specific properties of levan produced by recombinant levansucrase from B. subtilis 168 (Bs-SacB), often characterized as a bimodal distribution, that is, a mixture of low and high molecular weight levan. We found significant differences between both levans in terms of the already reported molecular weight, size and morphology using different analytical methods. The low molecular weight levan consists of a non-uniform polymer ranging from 50 to 230 kDa, synthesized through a non-processive mechanism that can spontaneously form spherical nanoparticles in the reaction medium. In contrast, high molecular weight levan is a uniform polymer, most probably synthesized through a processive mechanism, with an average molecular weight of 30,750 kDa and a poorly defined nano-structure. This is the first report exploring differences in morphology between low and high molecular weight levans. Our findings demonstrate that only the low molecular weight levan forms spherical nanoparticles in the reaction medium and that high molecular weight levan is mainly composed of a 33,000 kDa fraction with a microgel behavior.

Energy- and evolution-based design of inulosucrase for enhanced thermostability and inulin production

Inulosucrase from Lactobacillus reuteri 121 (LrInu) exhibits promise in the synthesis of prebiotic inulin and fructooligosaccharides. However, for its use in industry, LrInu's thermostability is a crucial consideration. In this study, the computational program FireProt was used to predict the thermostable variants of LrInu. Using rational criteria, nine variants were selected for protein expression and characterization. The G237P variant was determined to be the greatest designed candidate due to its greatly enhanced stability and activity in comparison to the wild-type enzyme. The optimum temperature of G237P increased from 50 to 60°C, with an over 5-fold increase in the half-life. Spectroscopy studies revealed that the G237P mutation could prevent the structural change in LrInu caused by heat or urea treatment. Molecular dynamics (MD) simulations showed that the enhanced thermostability of the G237P variant resulted from an increase in structural rigidity and the number of native contacts within the protein molecule. In addition, G237P variant synthesizes inulin with greater efficiency than WT. KEY POINTS: • Thermostable inulosucrase variant(s) were designed by Fireprot server. • G237P variant showed significantly improved thermostability compared to the wild type. • Inulin is synthesized more efficiently by G237P variant.

Enzymatic synthesis of fructooligosaccharides: From carrot discards to prebiotic juice

A great volume of carrots is discarded daily worldwide because they do not meet the required shape and size standards. However, they have the same nutritional characteristics as those commercialized, and can be used in different food products. Carrot juice is an excellent matrix for the development of functional foods with prebiotic compounds, such as fructooligosaccharides (FOS). In this work, the production of FOS in situ in carrot juice was evaluated using a fructosyltransferase from Aspergillus niger, produced by solid-state fermentation on carrot bagasse. The enzyme was partially purified 12.5-fold with a total yield of 93 %, and specific activity of 59 U/mg of protein by Sephadex G-105 molecular exclusion chromatography. It was identified by nano LC-MS/MS as a β-fructofuranosidase with a 63.6 kDa MW and it allowed obtaining a FOS yield of 31.6 % in carrot juice. The result was a prebiotic juice with a final concentration of 32.4 mg/mL of FOS. Using the commercial enzyme Viscozyme L a higher yield of FOS (39.8 %) was obtained in carrot juice, corresponding to a total amount of FOS of 54.6 mg/mL. This circular economy scheme allowed the obtention of a functional juice, that may contribute to improve health of consumers.

Purification of Aspergillus tamarii mycelial fructosyltransferase (m-FTase), optimized FOS production, and evaluation of its anticancer potential

In the present study, generation of prebiotic fructooligosaccharides (FOS) using Aspergillus tamarii FTase was optimized by applying response surface methodology. Optimal FOS (251 g L^-1 ) was generated at 28.4°C, pH 7.0 and 50% (w/v) sucrose leading to 1.97-fold yield enhancement. The m-FTase was purified using ultrafiltration followed by HiTrap Q HP anion exchange chromatography resulting in 2.15-fold purified FTase with 12.76 U mg^-1 specific activity. Purified FTase (75 kDa) had K_m and V_max values of 1049.717 mM and 2.094 µmol min^-1  mg^-1 , respectively. FOS incorporation led to upregulation of caspase 3, caspase 9, and Bax genes suggesting mitochondrial apoptosis activation in cancer cells. The study describes characteristics of purified FTase from A. tamarii, production optimization of FOS and unravels the role of FOS in anticancer activity against HT-29 cells. PRACTICAL APPLICATION: This study provides detailed insights of kinetic and thermodynamic characteristics of purified FTase, a prebiotic FOS-generating enzyme. Moreover, the role of the apoptotic genes involved in anticancer activity, and the prebiotic potential of FOS is also investigated. These findings are important in the context of FOS applications, and the optimized production strategies make it useful for industrial application.

Oligosaccharides production from coprophilous fungi: An emerging functional food with potential health-promoting properties

Functional foods are essential food products that possess health-promoting properties for the treatment of infectious diseases. In addition, they provide energy and nutrients, which are required for growth and survival. They occur as prebiotics or dietary supplements, including oligosaccharides, processed foods, and herbal products. However, oligosaccharides are more efficiently recognized and utilized, as they play a fundamental role as functional ingredients with great potential to improve health in comparison to other dietary supplements. They are low molecular weight carbohydrates with a low degree of polymerization. They occur as fructooligosaccharide (FOS), inulooligosaccharadie (IOS), and xylooligosaccahride (XOS), depending on their monosaccharide units. Oligosaccharides are produced by acid or chemical hydrolysis. However, this technique is liable to several drawbacks, including inulin precipitation, high processing temperature, low yields, and high production costs. As a consequence, the application of microbial enzymes for oligosaccharide production is recognized as a promising strategy. Microbial enzymatic production of FOS and IOS occurs by submerged or solid-state fermentation in the presence of suitable substrates (sucrose, inulin) and catalyzed by fructosyltransferases and inulinases. Incorporation of FOS and IOS enriches the rheological and physiological characteristics of foods. They are used as low cariogenic sugar substitutes, suitable for diabetics, and as prebiotics, probiotics and nutraceutical compounds. In addition, these oligosaccharides are employed as anticancer, antioxidant agents and aid in mineral absorption, lipid metabolism, immune regulation etc. This review, therefore, focuses on the occurrence, physico-chemical characteristics, and microbial enzymatic synthesis of FOS and IOS from coprophilous fungi. In addition, the potential health benefits of these oligosaccharides were discussed in detail.

Engineering a heterologously expressed fructosyltransferase from Aspergillus oryzae N74 in Komagataella phaffii (Pichia pastoris) for kestose production

Fructo-oligosaccharides (FOS) are one of the most well-studied and commercialized prebiotics. FOS can be obtained either by controlled hydrolysis of inulin or by sucrose transfructosylation. FOS produced from sucrose are typically classified as short-chain FOS (scFOS), of which the best known are 1-kestotriose (GF₂), 1,1-kestotetraose (GF₃), and 1,1,1-kestopentaose (GF₄), produced by fructosyltransferases (FTases) or β-fructofuranosidases. In previous work, FOS production was studied using the Aspergillus oryzae N74 strain, its ftase gene was heterologously expressed in Komagataella phaffii (Pichia pastoris), and the enzyme's tertiary structure modeled. More recently, residues that may be involved in protein-substrate interactions were predicted. In this study, the aim was to experimentally validate previous in silico results by independently producing recombinant wild-type A. oryzae N74 FTase and three single-point mutations in Komagataella phaffii (Pichia pastoris). The R163A mutation virtually abolished the transfructosylating activity, indicating a requirement for the positively charged arginine residue in the catalytic domain D. In contrast, transfructosylating activity was improved by introducing the mutations V242E or F254H, with V242E resulting in higher production of GF₂ without affecting that of GF₃. Interestingly, initial sucrose concentration, reaction temperature and the presence of metal cofactors did not affect the enhanced activity of mutant V242E. Overall, these results shed light on the mechanism of transfructosylation of the FTase from A. oryzae and expand considerations regarding the design of biotechnological processes for specific FOS production.

Fructooligosaccharides production by immobilized Pichia pastoris cells expressing Schedonorus arundinaceus sucrose:sucrose 1-fructosyltransferase

Fructooligosaccharides (FOSs)—fructose-based oligosaccharides—are typical prebiotics with health-promoting effects in humans and animals. The trisaccharide 1-kestotriose is the most attractive inulin-type FOS. We previously reported a recombinant sucrose:sucrose 1-fructosyltransferase (1-SST, EC 2.4.1.99) from Schedonorus arundinaceus (Sa) that efficiently converts sucrose into 1-kestotriose. In this study, Pichia pastoris PGFT6x-308 constitutively expressing nine copies of the Sa1-SST gene displayed fructosyltransferase activity in undisrupted biomass (49.8 U/ml) and culture supernatant (120.7 U/ml) in fed-batch fermentation (72 hr) with sugarcane molasses. Toluene permeabilization increased 2.3-fold the Sa1-SSTrec activity of whole cells entrapped in calcium-alginate beads. The reaction with refined or raw sugar (600 g/l) yielded 1-kestotriose and 1,1-kestotetraose in a ratio of 8:2 with their sum representing above 55% (wt/wt) of total carbohydrates. The FOSs yield decreased to 45% (wt/wt) when sugarcane syrup and molasses were used as cheaper sucrose sources. The beads retained 80% residual Sa1-SSTrec activity after a 30-day batchwise operation with refined cane sugar at 30°C and pH 5.5. The immobilized biocatalyst is attractive for the continuous production of short-chain FOSs, most particularly 1-kestotriose.

Production, properties, and applications of fructosyltransferase: a current appraisal

BACKGROUND

Fructosyltransferases (FTases) are drawing increasing attention due to their application in prebiotic fructooligosaccharide (FOS) generation. FTases have been reported to occur in a variety of microorganisms but are predominantly found in filamentous fungi. These are employed at the industrial scale for generating FOS which make the key ingredient in functional food supplements and nutraceuticals due to their bifidogenic and various other health-promoting properties.

SCOPE AND APPROACH

This review is aimed to discuss recent developments made in the area of FTase production, characterization, and application in order to present a comprehensive account of their present status to the reader. Structural features, catalytic mechanisms, and FTase improvement strategies have also been discussed in order to provide insight into these aspects.

KEY FINDINGS AND CONCLUSIONS

Although FTases occur in several plants and microorganisms, fungal FTases are being exploited commercially for industrial-scale FOS generation. Several fungal FTases have been characterized and heterologously expressed. However, considerable scope exists for improved production and application of FTases for cost-effective production of prebiotic FOS.HIGHLIGHTSFructosyltrasferase (FTase) is a key enzyme in fructo-oligosaccharide (FOS) generationDevelopments in the production, properties, and functional aspects of FTasesMolecular modification and immobilization strategies for improved FOS generationFructosyltransferases are innovation hotspots in the food and nutraceutical industries.

Decreased expression of fructosyltransferase genes in asparagus roots may contribute to efficient fructan degradation during asparagus spear harvesting

Asparagus (Asparagus officinalis L.) accumulates inulin and inulin neoseries-type fructans in root, which are synthesized by three fructosyltransferases-sucrose:sucrose 1-fructosyltransferase (1-SST, EC 2.4.1.99), fructan:fructan 1-fructosyltransferase (1-FFT, EC 2.4.1.100), and fructan:fructan 6^G-fructosyltransferase (6G-FFT, EC 2.4.1.243). Fructans in roots are considered as energy sources for emerging of spears, and it has been demonstrated that a gradual decrease in root fructan content occurs during the spear harvesting season (budding and shooting up period). However, the roles of certain three fructosyltransferases during the harvest season have not yet been elucidated. Here, we investigated the variation in enzymatic activities and gene expression levels of three fructosyltransferases and examined sugar contents in roots before and during the spear harvest period. Two cDNAs, aoft2 and aoft3, were isolated from the cDNA library of roots. The respective recombinant proteins (rAoFT2 and rAoFT3), produced by Pichia pastoris, were characterized: rAoFT2 showed 1-FFT activity (producing nystose from 1-kestose), whereas rAoFT3 showed 1-SST activity (producing 1-kestose from sucrose). These reaction profiles of recombinant proteins were similar to those of native enzymes purified previously. These results indicate that aoft2 and aoft3 encoding 1-FFT and 1-SST are involved in fructan synthesis in roots. A gradual downregulation of fructosyltransferase genes and activity of respective enzymes was observed in roots during the harvest period, which also coincided with the decrease in fructooligosaccharides and increase in fructose due to fructan exohydrolase activity. These findings suggest that downregulation of fructosyltransferases genes during harvest time may contribute to efficient degradation of fructan required for the emergence of spears.

Biochemical characterization of extracellular fructosyltransferase from Aspergillus oryzae IPT-301 immobilized on silica gel for the production of fructooligosaccharides

OBJECTIVE

Extracellular fructosyltransferase (FTase, E.C.2.4.1.9) from Aspergillus oryzae IPT-301 was immobilized on silica gel by adsorption and biochemically characterized aiming at its application in the transfructosylation reaction of sucrose for the production of fructooligossaccarides (FOS).

RESULTS

The transfructosylation activity (A_T) was maximized by the experimental design in function of the reaction pHs and temperatures. The A_T of the immobilized enzyme showed the kinetics behavior described by the Hill model. The immobilized FTase showed reuse capacity for six consecutive reaction cycles and higher pH and thermal stability than the soluble enzyme.

CONCLUSION

These results suggest a high potential of application of silica gel as support for FTase immobilization aiming at FOS production.

Purification and biochemical characterization of an extracellular fructosyltransferase enzyme from Aspergillus niger sp. XOBP48: implication in fructooligosaccharide production

An extracellular fructosyltransferase (Ftase) enzyme with a molar mass of ≈70 kDa from a newly isolated indigenous coprophilous fungus Aspergillus niger sp. XOBP48 is purified to homogeneity and characterized in this study. The enzyme was purified to 4.66-fold with a total yield of 15.53% and specific activity of 1219.17 U mg^-1 of protein after a three-step procedure involving (NH₄)₂SO₄ fractionation, dialysis and anion exchange chromatography. Ftase showed optimum activity at pH 6.0 and temperature 50 °C. Ftase exhibited over 80% residual activity at pH range of 4.0-10.0 and ≈90% residual activity at temperature range of 40-60 °C for 6 h. Metal ion inhibitors Hg²⁺ and Ag⁺ significantly inhibited Ftase activity at 1 mmol concentration. Ftase showed K _m, v _max and k _cat values of 79.51 mmol, 45.04 µmol min^-1 and 31.5 min^-1, respectively, with a catalytic efficiency (k _cat/K _m) of 396 µmol^-1 min^-1 for the substrate sucrose. HPLC-RI experiments identified the end products of fructosyltransferase activity as monomeric glucose, 1-kestose (GF₂), and 1,1-kestotetraose (GF₃). This study evaluates the feasibility of using this purified extracellular Ftase for the enzymatic synthesis of biofunctional fructooligosaccharides.

Implications of the mutation S164A on Bacillus subtilis levansucrase product specificity and insights into protein interactions acting upon levan synthesis

Mutation S164A largely affects the transfructosylation properties of Bacillus subtilis levansucrase (SacB). The variant uses acceptors such as glucose and short levans with an average molecular weight of 7.6 kDa more efficiently than SacB, leading to the enhanced synthesis of medium and high molecular weight polymer and a blasto-oligosaccharide series with a polymerization degree of 2-10. A 3-fold increase in blasto-oligosaccharides yield is provoked by the modified interplay between the variant and glucose. Despite its modified product specificity, protein-carbohydrate and protein-protein interactions are still a major factor affecting size and distribution of levan molecular weight. This study highlights the importance of critical factors such as protein concentration in the analysis of wild-type and mutagenized levansucrases. Docking experiments with the crystal structures of SacB and variant S164A - the latter obtained at a 2.6 Å resolution - identified unreported potential binding subsites for fructosyl moieties on the surface of both enzymes.

Purification and biochemical characteristics of a novel fructosyltransferase with a high FOS transfructosylation activity from Aspergillus oryzae S719

Fructooligosaccharides (FOS) have widely used for the manufacture of low-calorie and functional foods, because they can inhibit intestinal pathogenic microorganism growth and increase the absorption of Ca²⁺ and Mg²⁺. In this study, the novel fructosyltransferase (FTase) from Aspergillus oryzae strain S719 was successfully purified and characterized. The specific activity of the final purified material was 4200 mg^-1 with purification ratio of 66 times and yield of 26%. The molecular weight of FTase of A. oryzae S719 was around 95 kDa by SDS-PAGE, which was identified as a type of FTase by Mass Spectrometry (MS). The purified FTase had optimum temperature and pH of 55 °C and 6.0, respectively. The FTase showed to be stable with more than 80% of its original activity at room temperature after 12 h and maintaining activity above 90% at pH 4.0-11.0. The Km and kcat values of the FTase were 310 mmol L^-1 and 2.0 × 10³ min^-1, respectively. The FTase was activated by 5 mmol L^-1 Mg²⁺ and 10 mmol L^-1 Na⁺ (relative activity of 116 and 114%, respectively), indicating that the enzyme was Mg²⁺ and Na⁺ dependent. About 64% of FOS was obtained by the purified FTase under 500 g L^-1 sucrose within 4 h of reaction time, which was the shortest reaction time to be reported regarding the purified enzyme production of FOS. Together, these results indicated that the FTase of A. oryzae S719 is an excellent candidate for the industrial production of FOS.

Comparison of the Levansucrase from the epiphyte Erwinia tasmaniensis vs its homologue from the phytopathogen Erwinia amylovora

Erwinia tasmaniensis is an epiphytic bacterium related to the plant pathogen Erwinia amylovora, the etiological agent of fire blight. In this study the levansucrase from E. tasmaniensis (EtLsc) has been compared with the homologous enzyme from E. amylovora (EaLsc). We characterized the enzymatic activity and compared the products profile of both enzymes by High Performance Anion Exchange Chromatography coupled with Pulsed Amperometric Detector (HPAEC-PAD). Moreover we determined the crystal structure of EtLsc to understand the structural peculiarity causing the different product profiles of the two homologues. EtLsc exhibits increased efficiency in the production of FOS, resulting in a better catalyst for biotechnological synthesis than EaLsc. Based on our results, we propose that the role of this enzyme in the life cycle of the two bacteria is most likely related to survival, rather than linked to pathogenicity in E. amylovora.

In Silico insights on enhancing thermostability and activity of a plant Fructosyltransferase from Pachysandra terminalis via introduction of disulfide bridges

Drawbacks of industrially-used fructosyltransferases (FTs) such as low optimum temperature and low fructooligosaccharides (FOS) yield necessitates the search for engineered FTs that are highly thermostable and active. With the availability of the first plant FT crystal structure from Pachysandra terminalis (PDB ID: 3UGH), computer-aided protein engineering of plant FT is now feasible. To obtain insights on the effect of specific mutations i.e. disulfide bridge introduction, wild-type and mutant FTs were subjected to a 15 μs Martini Coarse-grained Molecular Dynamics (CGMD) simulations at 303 K and 334 K. We report here the five mutants, M31C-Q49C, L144C-S193C, P34C-W300C, S219C-L226C and V470C-S498C with enhanced thermostabilities and/or activities relative to the wild type. Interestingly, M31C-Q49C, which is located within the catalytic-carrying blade of the catalytic domain, has an activity enhancement at both temperatures. At 334 K, three mutations, L144C-S193C, P34C-W300C and V470C-S498C, achieved thermostability relative to the wild type. Intriguingly, both activity and stability enhancement exhibited only at 334 K can be achieved provided that the mutation is located either on the catalytic-carrying residue blade of the catalytic domain or on the non-catalytic domain. Our results suggest that V470C-S498C and L144C-S193C are promising mutants and that domain-specific approach may be exploited to customize enzyme properties.

High level production of a recombinant acid stable exoinulinase from Aspergillus kawachii

Exoinulinases-enzymes extensively studied in recent decades because of their industrial applications-need to be produced in suitable quantities in order to meet production demands. We describe here the production of an acid-stable recombinant inulinase from Aspergillus kawachii in the Pichia pastoris system and the recombinant enzyme's biochemical characteristics and potential application to industrial processes. After an appropriate cloning strategy, this genetically engineered inulinase was successfully overproduced in fed-batch fermentations, reaching up to 840 U/ml after a 72-h cultivation. The protein, purified to homogeneity by chromatographic techniques, was obtained at a 42% yield. The following biochemical characteristics were determined: the enzyme had an optimal pH of 3, was stable for at least 3 h at 55 °C, and was inhibited in catalytic activity almost completely by Hg⁺². The respective K_m and V_max for the recombinant inulinase with inulin as substrate were 1.35 mM and 2673 μmol/min/mg. The recombinant enzyme is an exoinulinase but also possesses synthetic activity (i. e., fructosyl transferase). The high level of production of this recombinant plus its relevant biochemical properties would argue that the process presented here is a possible recourse for industrial applications in carbohydrate processing.

Expression and Activity Analysis of Fructosyltransferase from Aspergillus oryzae

The fructosyltransferase gene was isolated and cloned from Aspergillus oryzae. The gene was 1368 bp, which encoded a protein of 455 amino acids. To analyze the activity of the expressed fructosyltransferase, the pET32a-fructosyltransferase recombined plasmid was transformed into Escherichia coli BL21. The fructosyltransferase gene was successfully expressed by Isopropyl-β-d-thiogalactoside (IPTG) induction. The molecular weight of the expression protein was about 45 kDa. The optimal conditions of protein expression were 25 °C, 0.1 mM IPTG, and 8 h of inducing time. The optimal concentration of urea dealing with inclusion body was 2.5 M. The expressed protein exhibited a strong fructosyl transfer activity. These results showed that the expressed fructosyltransferas owned transferase activity, and could catalyze the synthesis of sucrose-6-acetate.

Effects of nonionic surfactants on pellet formation and the production of β-fructofuranosidases from Aspergillus oryzae KB

Aspergillus oryzae KB produces two β-fructofuranosidases (F1 and F2). F1 has high transferring activity and produces fructooligosaccharides from sucrose. Mycelial growth pellets were altered by the addition of Tween 20, 40 and 80 (HLB=16.7, 15.6 and 15.0, respectively) in liquid medium cultures to form small spherical pellets. The particle size of the pellets decreased with the HLB value, which corresponds to an increase in surfactant hydrophobicity. Selective F1 production and pellet size were maximized using Tween 20. Adding polyoxyethylene oleyl ethers (POEs) with various degrees of polymerization (2, 7, 10, 20 and 50: HLB=7.7, 10.7, 14.7, 17.2 and 18.2, respectively) was investigated. A minimum mean particle size was obtained using a POE with DP=10, HLB=14.7. The POE surfactants had little effect on the selective production of F1. The formation of filamentous pellets depended on the surfactant HLB value, and F1 enzymes were produced most efficiently using Tween 20.

Enhancement of fructosyltransferase and fructooligosaccharides production by A. oryzae DIA-MF in Solid-State Fermentation using aguamiel as culture medium

The aim of this work was to improve the production of fructosyltransferase (FTase) by Solid-State Fermentation (SSF) using aguamiel (agave sap) as culture medium and Aspergillus oryzae DIA-MF as producer strain. SSF was carried out evaluating the following parameters: inoculum rate, incubation temperature, initial pH and packing density to determine the most significant factors through Box-Hunter and Hunter design. The significant factors were then further optimized using a Box-Behnken design and response surface methodology. The maximum FTase activity (1347U/L) was obtained at 32°C, using packing density of 0.7g/cm(3). Inoculum rate and initial pH had no significant influence on the response. FOS synthesis applying the enzyme produced by A. oryzae DIA-MF was also studied using aguamiel as substrate.

Bacillus subtilis 168 levansucrase (SacB) activity affects average levan molecular weight

Levan is a fructan polymer that offers a variety of applications in the chemical, health, cosmetic and food industries. Most of the levan applications depend on levan molecular weight, which in turn depends on the source of the synthesizing enzyme and/or on reaction conditions. Here we demonstrate that in the particular case of levansucrase from Bacillus subtilis 168, enzyme concentration is also a factor defining the molecular weight levan distribution. While a bimodal distribution has been reported at the usual enzyme concentrations (1 U/ml equivalent to 0.1 μM levansucrase) we found that a low molecular weight normal distribution is solely obtained al high enzyme concentrations (>5 U/ml equivalent to 0.5 μM levansucrase) while a high normal molecular weight distribution is synthesized at low enzyme doses (0.1 U/ml equivalent to 0.01 μM of levansucrase).

Fructan metabolism and expression of genes coding fructan metabolic enzymes during cold acclimation and overwintering in timothy (Phleum pratense)

Metabolism of fructans in temperate grasses dynamically fluctuates before and during winter and is involved in the overwintering activity of plants. We monitored three candidate factors that may be involved in seasonal fructan metabolism in timothy (Phleum pratense): transcription levels of two fructosyltransferase (PpFT1 and PpFT2) genes and one fructan exohydrolase (Pp6-FEH1) gene during fall and winter and under artificially cold conditions. Functional analysis using a recombinant enzyme for PpFT2, a novel fructosyltransferase cDNA, revealed that it encoded sucrose:fructan 6-fructosyltransferase, with enzymatic properties different from previously characterized PpFT1. PpFT1 transcripts decreased from September to December as the amount of fructans increased, whereas PpFT2 transcripts increased in timothy crowns. PpFT2 was transcriptionally more induced than PpFT1 in response to cold and sucrose in timothy seedlings. A rapid increase in Pp6-FEH1 transcripts and increased monosaccharide content were observed in timothy crowns when air temperature was continuously below 0°C and plants were not covered by snow. Transcriptional induction of Pp6-FEH1 by exposure to -3°C was also observed in seedlings. These findings suggest Pp6-FEH1 involvement in the second phase of hardening. PpFT1 and PpFT2 transcription levels decreased under snow cover, whereas Pp6-FEH1 transcription levels were constant, which corresponded with the fluctuation of fructosyltransferase and fructan exohydrolase activities. Inoculation with snow mold fungi (Typhula ishikariensis) increased Pp6-FEH1 transcription levels and accelerated hydrolysis of fructans. These results suggest that transcriptional regulation of genes coding fructan metabolizing enzymes is partially involved in the fluctuation of fructan metabolism during cold acclimation and overwintering.

Mutagenesis of Aspergillus Oryzae IPT-301 to improve the production of β-Fructofuranosidase

Aspergillus oryzae IPT-301, previously reported as a β-fructofuranosidase producing microorganism, was successfully mutated using UV irradiation at 253.7 nm followed by the screening of survivors resistant to certain stress conditions. Strains were first subjected to the β-fructofuranosidase activity assay using a portion from the colony grown in Petri dish as the enzyme source. Seven mutants with β-fructofuranosidase activity values relative to the parent culture between 140 - 190% were selected from survivors grown at temperature of 40ºC or 0.018% (w/v) sodium dodecyl sulfate concentration. They were cultivated on a rotary shaker to characterize mycelium and extracellular fructosyltransferase activities. Three mutants named IPT-745, IPT-746 and IPT-748 showed the highest amount of mycelium activity whose values increased 1.5 - 1.8 fold, compared with the parent strain. It was found that more than 55% of total enzyme activity (mycelium- plus extracellular- activity) from these strains was detected in the mycelium fraction. Only one mutant, IPT-747, exceeded the amount of extracellular enzyme exhibited by the parent strain (1.5 times). This mutant also showed the highest value of total fructosyltransferase activity.