Immobilization of Aspergillus japonicus by entrapping cells in gluten for production of fructooligosaccharides

Isolation and identification of Zalaria sp. Him3 as a novel fructooligosaccharides-producing yeast

AIMS

This study aimed at obtaining a novel fructooligosaccharides (FOS)-producing yeast, which was different from conventional FOS producers, Aureobasidium spp.

METHODS AND RESULTS

Strain Him3 was newly isolated from a Japanese dried sweet potato as a FOS producer. The strain exhibited yeast-like cells and melanization on the potato dextrose agar medium, and formed very weak pseudomycelia on the yeast extract polypeptone dextrose agar medium. Based on the internal transcribed spacer (ITS) region of ribosomal DNA and a partial β-tubulin gene sequences, the strain Him3 was identified as Zalaria sp. The β-fructofuranosidase (FFase) produced by strain Him3 was localized on the cell surface (CS-FFase) as well as in the culture broth (EC-FFase). The FOS production yields by CS-FFase and EC-FFase from 50% sucrose were 63.8% and 64.6%, respectively, to consumed sucrose after the reaction for 72 h.

CONCLUSIONS

We successfully isolated a novel black yeast, Zalaria sp. Him3, with effective capacity for FOS production. Phylogenetic analysis revealed that strain Him3 was distantly related with the conventional FOS producers, Aureobasidium spp.

SIGNIFICANCE AND IMPACT OF THE STUDY

Since FFase of strain Him3 demonstrated high production yields of FOS, it could be applied to novel industrial production of FOS, which is different from conventional methods.

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 of fructooligosaccharides by Bacillus subtilis natto CCT7712 and their antiproliferative potential

AIMS

Fructooligosaccharides (FOSs) known for their health properties and β-(2→6)-levan-type FOSs have shown prebiotic and immunomodulatory activities that overcome those of commercial β-(2→1)-FOSs, but costs do not favour their use. Moreover, FOSs can reach the bloodstream through the diet, and little is known about their direct effect on cells. The aim of this work was to produce high-content FOSs by Bacillus subtilis natto CCT7712 in a bioreactor using commercial sucrose and to evaluate their antiproliferative effects in OVCAR-3 cells.

METHODS AND RESULTS

FOS production reached 173·60 g l^-1 , 0·2 vvm aeration and uncontrolled pH. Levan-type FOSs, composed of β-(2 → 6) links and mainly GF₃ (6-nystose), were identified using RMN spectroscopy, FT-IR and ESI-MS. FOSs decreased the viability and proliferation of OVCAR-3 cells, and the effects were associated with an increased pro-inflammatory response by the induction of IL-8 and TNF-α, and the repression of ER-β genes. The metabolic profiles showed disruption of cellular homeostasis that can be associated with a decrease in proliferation.

CONCLUSIONS

The high production of levan-type FOSs from B. subtilis natto CCT7712 in a bioreactor was achieved, and they showed antiproliferative potential in OVCAR-3 cells.

SIGNIFICANCE AND IMPACT OF THE STUDY

FOS could be a good target for future therapeutic studies and commercial use.

Establishment of a rapid and effective plate chromogenic assay for screening of Aspergillus species with high β-fructofuranosidase activity for fructooligosaccharides production

Fructooligosaccharides (FOS) are commonly regarded as prebiotics and used as components of functional foods. Currently, the industrial sucrose-to-FOS biotransformation is mainly carried out using the microbial-derived β-fructofuranosidases with transglycosylation activity as catalysts. Evaluation of the ability of a microorganism to produce β-fructofuranosidase is commonly conducted by measuring enzyme activity. However, the traditional method requires several steps to identify strains with high β-fructofuranosidase activity, which is not suitable for high-throughput screening. To facilitate screening of a large number of microbial cultures, this study developed a plate chromogenic assay method based on the glucose oxidase (GOD) - peroxidase (POD) bienzymatic system for screening of β-fructofuranosidase-producing fungal strains and predicting their potential to produce FOS. This method used the amount of glucose released from sucrose as indicator to form clear pink halos around the microbial colonies with β-fructofuranosidase activity. Cultivation conditions for the plate assay were optimized as cultivation time 5 h and spore inoculum concentration 10⁸/ml. Moreover, the method was applied to screening of an Aspergillus niger ATCC 20611 mutant library. The mutant A11 displaying the largest pink halo was screened out and its β-fructofuranosidase activity was determined to be 1.65 fold than that of the parental strain. Thin layer chromatography (TLC) assay further indicated that A11 with the largest halo possessed the highest FOS synthesis ability. These results demonstrated the potential of this plate chromogyenic assay method in the rapid and effective identification of excellent FOS producers from a large number of strain samples.

Amberlite IRA 900 versus calcium alginate in immobilization of a novel, engineered β-fructofuranosidase for short-chain fructooligosaccharide synthesis from sucrose

The immobilization of β-fructofuranosidase for short-chain fructooligosaccharide (scFOS) synthesis holds the potential for a more efficient use of the biocatalyst. However, the choice of carrier and immobilization technique is a key to achieving that efficiency. In this study, calcium alginate (CA), Amberlite IRA 900 (AI900) and Dowex Marathon MSA (DMM) were tested as supports for immobilizing a novel engineered β-fructofuranosidase from Aspergillus japonicus for scFOS synthesis. Several immobilization parameters were estimated to ascertain the effectiveness of the carriers in immobilizing the enzyme. The performance of the immobilized biocatalysts are compared in terms of the yield of scFOS produced and reusability. The selection of carriers and reagents was motivated by the need to ensure safety of application in the production of food-grade products. The CA and AI900 both recorded impressive immobilization yields of 82 and 62%, respectively, while the DMM recorded 47%. Enzyme immobilizations on CA, AI900 and DMM showed activity recoveries of 23, 27, and 17%, respectively. The CA, AI900 immobilized and the free enzymes recorded their highest scFOS yields of 59, 53, and 61%, respectively. The AI900 immobilized enzyme produced a consistent scFOS yield and composition for 12 batch cycles but for the CA immobilized enzyme, only 6 batch cycles gave a consistent scFOS yield. In its first record of application in scFOS production, the AI900 anion exchange resin exhibited potential as an adequate carrier for industrial application with possible savings on cost of immobilization and reduced technical difficulty.

Enhancing fructooligosaccharides production by genetic improvement of the industrial fungus Aspergillus niger ATCC 20611

Aspergillus niger ATCC20611 is one of the most potent filamentous fungi used commercially for production of fructooligosaccharides (FOS), which are prospective components of functional food by stimulating probiotic bacteria in the human gut. However, current strategies for improving FOS yield still rely on production process development. The genetic engineering approach hasn't been applied in industrial strains to increase FOS production level. Here, an optimized polyethylene glycol (PEG)-mediated protoplast transformation system was established in A. niger ATCC 20611 and used for further strain improvement. The pyrithiamine resistance gene (ptrA) was selected as a dominant marker and protoplasts were prepared with high concentration (up to 10⁸g^-1 wet weight mycelium) by using mixed cell wall-lysing enzymes. The transformation frequency with ptrA can reach 30-50 transformants per μg of DNA. In addition, the efficiency of co-transformation with the EGFP reporter gene (egfp) was high (approx. 82%). Furthermore, an activity-improved variant of β-fructofuranosidase, FopA(A178P), was successfully overexpressed in A. niger ATCC 20611 by using the transformation system. The transformant, CM6, exhibited a 58% increase in specific β-fructofuranosidase activity (up to 507U/g), compared to the parental strain (320U/g), and effectively reduced the time needed for completion of FOS synthesis. These results illustrate the feasibility of strain improvement through genetic engineering for further enhancement of FOS production level.

Fructo-oligosaccharides: Production, Purification and Potential Applications

The nutritional and therapeutic benefits of prebiotics have attracted the keen interest of consumers and food processing industry for their use as food ingredients. Fructo-oligosaccharides (FOS), new alternative sweeteners, constitute 1-kestose, nystose, and 1-beta-fructofuranosyl nystose produced from sucrose by the action of fructosyltransferase from plants, bacteria, yeast, and fungi. FOS has low caloric values, non-cariogenic properties, and help gut absorption of ions, decrease levels of lipids and cholesterol and bifidus-stimulating functionality. The purified linear fructose oligomers are added to various food products like cookies, yoghurt, infant milk products, desserts, and beverages due to their potential health benefits. This review is focused on the various aspects of biotechnological production, purification and potential applications of fructo-oligosaccharides.

Biotechnological production and application of fructooligosaccharides

Currently, prebiotics are all carbohydrates of relatively short chain length. One important group is the fructooligosaccharides (FOS), a special kind of prebiotic associated to the selective stimulation of the activity of certain groups of colonic bacteria. They have a positive and beneficial effect on intestinal microbiota, reducing the incidence of gastrointestinal infections and also possessing a recognized bifidogenic effect. Traditionally, these prebiotic compounds have been obtained through extraction processes from some plants, as well as through enzymatic hydrolysis of sucrose. However, different fermentative methods have also been proposed for the production of FOS, such as solid-state fermentations utilizing various agro-industrial by-products. By optimizing the culture parameters, FOS yields and productivity can be improved. The use of immobilized enzymes and cells has also been proposed as being an effective and economic method for large-scale production of FOS. This article is an overview of the results considering recent studies on FOS biosynthesis, physicochemical properties, sources, biotechnological production and applications.

Recent developments in manufacturing oligosaccharides with prebiotic functions

The market for prebiotics is steadily growing. To satisfy this increasing worldwide demand, the introduction of effective bioprocessing methods and implementation strategies is required. In this chapter, we review recent developments in the manufacture of galactooligosaccharides (GOS) and fructooligosaccharides (FOS). These well-established oligosaccharides (OS) provide several health benefits and have excellent technological properties that make their use as food ingredients especially attractive. The biosyntheses of lactose-based GOS and sucrose-based FOS show similarities in terms of reaction mechanisms and product formation. Both GOS and FOS can be synthesized using whole cells or (partially) purified enzymes in immobilized or free forms. The biocatalysis results in a final product that consists of OS, unreacted disaccharides, and monosaccharides. This incomplete conversion poses a challenge to manufacturers because an enrichment of OS in this mixture adds value to the product. For removing digestible carbohydrates from OS, a variety of bioengineering techniques have been investigated, including downstream separation technologies, additional bioconversion steps applying enzymes, and selective fermentation strategies. This chapter summarizes the state-of-the-art manufacturing strategies and recent advances in bioprocessing technologies that can lead to new possibilities for manufacturing and purifying sucrose-based FOS and lactose-based GOS.

Synthesis of fructooligosaccharides from Aspergillus niger commercial inulinase immobilized in montmorillonite pretreated in pressurized propane and LPG

Commercial inulinase from Aspergillus niger was immobilized in montmorillonite and then treated in pressurized propane and liquefied petroleum gas (LPG). Firstly, the effects of system pressure, exposure time, and depressurization rate, using propane and LPG, on enzymatic activity were evaluated through central composite design 2³. Residual activities of 145.1 and 148.5% were observed for LPG (30 bar, 6 h, and depressurization rate of 20 bar min⁻¹) and propane (270 bar, 1 h, and depressurization rate of 100 bar min⁻¹), respectively. The catalysts treated at these conditions in both fluids were then used for the production of fructooligosaccharides (FOS) using sucrose and inulin as substrates in aqueous and organic systems. The main objective of this step was to evaluate the yield and productivity in FOS, using alternatives for enhancing enzyme activity by means of pressurized fluids and also using low-cost supports for enzyme immobilization, aiming at obtaining a stable biocatalyst to be used for synthesis reactions. Yields of 18% were achieved using sucrose as substrate in aqueous medium, showing the potential of this procedure, hence suggesting a further optimization step to increase the process yield.

New improved method for fructooligosaccharides production by Aureobasidium pullulans

Fructooligosaccharides are prebiotics with numerous health benefits within which the improvement of gut microbiota balance can be highlighted, playing a key role in individual health. In this study, an integrated one-stage method for FOS production via sucrose fermentation by Aureobasidium pullulans was developed and optimized using experimental design tools. Optimization of temperature and agitation speed for maximizing the FOS production was performed using response surface methodology. Temperature was found to be the most significant parameter. The optimum fermentation conditions were found to be 32 °C and 385 rpm. Under these conditions, the model predicted a total FOS production yield of 64.7 gFOS/gsucrose. The model was validated at optimal conditions in order to check its adequacy and accuracy and an experimental yield of 64.1 (±0.0) gFOS/gsucrose was obtained. A significant improvement of the total FOS production yields by A. pullulans using a one-stage process was obtained.

Production of fructooligosaccharides by beta-fructofuranosidases from Aspergillus oryzae KB

Aspergillus oryzae KB produces two types of beta-fructofuranosidases: F1 and F2. F1 produces the fructooligosaccharides (FOSs) 1-kestose, nystose, and fructosyl nystose from sucrose through a transfructosylation action, whereas F2 mainly hydrolyzes sucrose to glucose and fructose. F1 and F2 enzymes were more selectively produced from the KB strain in liquid media with a sucrose concentration>2% and <2%, respectively. Immobilization using an anion-exchange resin (WA-30; polystyrene with tertiary amine) and cross-linking with glutaraldehyde depressed the hydrolysis reaction of F2 (high hydrolyzing enzyme) alone and enhanced the thermal stability of F1 (high transferring enzyme). F1 enzyme produced in the high sucrose medium was immobilized, cross-linked, and packed in a tubular reactor for continuous production of FOSs (24.6% 1-kestose, 21.6% nystose, 5.7% and fructosyl nystose). In a long-term operation in which 60% sucrose was imputed at 55 degrees C, the composition of FOSs produced was 51.9% (transfer ratio: 92%), and production by the immobilized enzyme was maintained for 984 h.

beta-Fructofuranosidase production by repeated batch fermentation with immobilized Aspergillus japonicus

The fungus Aspergillus japonicus ATCC 20236 was immobilized in vegetal fiber and used in repeated batch fermentations of sucrose (200 g/l) for the production of beta-fructofuranosidases (FFase). The assays were performed during eight consecutive cycles that were completed in a total period of 216 h. After each 24-h cycle of fermentation (except for the first cycle, which lasted 48 h), the fermented broth was replaced by fresh medium, and the FFase activity was determined in the replaced medium. The average value of FFase activity was a constant 40.6 U/ml at the end of the initial seven cycles, but had decreased by 22% at the end of the eighth cycle. Concurrent with these high and constant FFase values, the hydrolyzing activity of this enzyme increased during the cycles, while the transfructosylating activity decreased. As a consequence, the maximum production of fructooligosaccharides of 134.60 g/l observed in the initial 30 h of fermentation (first cycle) had gradually decreased by the end of the subsequent cycles, reaching approximately 23% of this value during cycles 4-8. Based on these results, we conclude that the present immobilization system has a great potential for application in a semi-continuous process for the production of FFase, but further studies are necessary to maintain the FFase transfructosylation activity at high levels during the overall process.

Microbial production of fructosyltransferases for synthesis of pre-biotics

Fructooligosaccharides (FOS) are prebiotic substances found in several vegetable or natural foods. The main commercial production of FOS comes from enzymatic transformation of sucrose by the microbial enzyme fructosyltransferase. The development of more efficient enzymes, with high activity and stability, is required and this has attracted the interest of biotechnologists and microbiologists with production by several microorganisms being studied. This article reviews and discusses FOS chemical structure, enzyme characteristics, the nomenclature, producer microorganisms and enzyme production both in solid state fermentation and submerged cultivation.

Screening of β-fructofuranosidase-producing microorganisms and effect of pH and temperature on enzymatic rate

Seventeen different strains of filamentous fungi were grown in batch cultures to compare their abilities for the production of beta-fructofuranosidase. Three of them, Aspergillus oryzae IPT-301, Aspergillus niger ATCC 20611 and strain IPT-615, showed high production with total fructosyltransferase activity higher than 12,500 units l(-1). In addition, the beta-fructofuranosidases of those strains have a high fructosyltransferase activity-to-hydrolytic activity ratio. The temperature and pH effects on the sucrose-beta-fructofuranosidase reaction rate were studied using a 2(2) factorial experimental design. The comparative analysis of the tested variable coefficients shows that the variable pH contributes mostly to the changes in the fructosyltransferase and hydrolytic rates and in the V (t)/V (h) ratio. At 40 and 50 degrees C, there were no significant differences between the fructosyltransferase and hydrolytic velocities of these enzymes.