Evaluation of the performance of an engineered β-fructofuranosidase from Aspergillus fijiensis to produce short-chain fructooligosaccharides from industrial sugar streams

Evaluation of different glycerol fed-batch strategies in a lab-scale bioreactor for the improved production of a novel engineered β-fructofuranosidase enzyme in Pichia pastoris

The β-fructofuranosidase enzyme from Aspergillus niger has been extensively used to commercially produce fructooligosaccharides from sucrose. In this study, the native and an engineered version of the β-fructofuranosidase enzyme were expressed in Pichia pastoris under control of the glyceraldehyde-3-phosphate dehydrogenase promoter, and production was evaluated in bioreactors using either dissolved oxygen (DO-stat) or constant feed fed-batch feeding strategies. The DO-stat cultivations produced lower biomass concentrations but this resulted in higher volumetric activity for both strains. The native enzyme produced the highest volumetric enzyme activity for both feeding strategies (20.8% and 13.5% higher than that achieved by the engineered enzyme, for DO-stat and constant feed, respectively). However, the constant feed cultivations produced higher biomass concentrations and higher volumetric productivity for both the native as well as engineered enzymes due to shorter process time requirements (59 h for constant feed and 155 h for DO-stat feed). Despite the DO-stat feeding strategy achieving a higher maximum enzyme activity, the constant feed strategy would be preferred for production of the β-fructofuranosidase enzyme using glycerol due to the many industrial advantages related to its enhanced volumetric enzyme productivity.

A review of fructosyl-transferases from catalytic characteristics and structural features to reaction mechanisms and product specificity

Carbohydrate-active enzymes are accountable for the synthesis and degradation of glycosidic bonds among diverse carbohydrates. Fructosyl-transferases represent a subclass of these enzymes, employing sucrose as a substrate to generate fructooligosaccharides (FOS) and fructan polymers. This category primarily includes levansucrase (LS, EC 2.4.1.10), inulosucrase (IS, EC 2.4.1.9), and β-fructofuranosidase (Ffase, EC 3.2.1.26). These three enzymes possess a similar five-bladed β-propeller fold and employ an anomer-retaining reaction mechanism mediated by nucleophiles, transition state stabilizers, and general acids/bases. However, they exhibit distinct product profiles, characterized by variations in linkage specificity and molecular mass distribution. Consequently, this article comprehensively explores recent advancements in the catalytic characteristics, structural features, reaction mechanisms, and product specificity of levansucrase, inulosucrase, and β-fructofuranosidase (abbreviated as LS, IS, and Ffase, respectively). Furthermore, it discusses the potential for modifying catalytic properties and product specificity through structure-based design, which enables the rational production of custom fructan and FOS.

A novel β-fructofuranosidase produced by Penicillium citreonigrum URM 4459: purification and biochemical features

Fructooligosaccharides (FOS) are prebiotics of interest to the food industry. These compounds can be produced through the transfructosylation reaction by the enzyme fructofuranosidase. This enzyme is widely produced by fungi in a medium rich in sugar. Therefore, in this work, the main objectives were production, purification, biochemical characterization of a novel fructofuranosidase enzyme by Penicillium citreonigrum URM 4459 and synthesize and evaluate the antibacterial potential of fructooligosaccharides. With respect to sucrose hydrolysis, the optimal pH was 5.5, the apparent Km for purified FFase was 3.8 mM, the molecular mass was 43.0 kDa, estimated by gel filtration on Superdex increase G75 controlled by AKTA Avant 25 and confirmed by 10% SDS-PAGE under denaturing condition. Also, the isoelectric point was 4.9. The fractions obtained with enzymatic activities, both stable at acidic pH and high temperatures, as well as being able to produce FOS. Regarding antibacterial activity, the FOS produced in this study showed better results than commercial FOS and other carbon sources. Thus, this work presents relevant data for the use of P. citreonigum to produce fructofuranosidase and consequently FOS and can be used in the food and pharmaceutical industry.

Tailoring fructooligosaccharides composition with engineered Zymomonas mobilis ZM4

Zymomonas mobilis ZM4 is an attractive host for the development of microbial cell factories to synthesize high-value compounds, including prebiotics. In this study, a straightforward process to produce fructooligosaccharides (FOS) from sucrose was established. To control the relative FOS composition, recombinant Z. mobilis strains secreting a native levansucrase (encoded by sacB) or a mutated β-fructofuranosidase (Ffase-Leu196) from Schwanniomyces occidentalis were constructed. Both strains were able to produce a FOS mixture with high concentration of 6-kestose. The best results were obtained with Z. mobilis ZM4 pB1-sacB that was able to produce 73.4 ± 1.6 g L^-1 of FOS, with a productivity of 1.53 ± 0.03 g L^-1 h^-1 and a yield of 0.31 ± 0.03 g_FOS g_sucrose^-1. This is the first report on the FOS production using a mutant Z. mobilis ZM4 strain in a one-step process. KEY POINTS: • Zymomonas mobilis was engineered to produce FOS in a one-step fermentation process. • Mutant strains produced FOS mixtures with high concentration of 6-kestose. • A new route to produce tailor-made FOS mixtures was presented.

Successive Fermentation of Aguamiel and Molasses by Aspergillus oryzae and Saccharomyces cerevisiae to Obtain High Purity Fructooligosaccharides

Fructooligosaccharides (FOS) are usually synthesized with pure enzymes using highly concentrated sucrose solutions. In this work, low-cost aguamiel and molasses were explored as sucrose alternatives to produce FOS, via whole-cell fermentation, with an Aspergillus oryzae DIA-MF strain. FOS production process was optimized through a central composite experimental design, with two independent variables: initial sucrose concentration in a medium composed of aguamiel and molasses (AgMe), and inoculum concentration. The optimized process—165 g/L initial sucrose in AgMe (adjusted with concentrated molasses) and 1 × 10⁷ spores/mL inoculum concentration—resulted in an FOS production of 119 ± 12 g/L and a yield of 0.64 ± 0.05 g _FOS/g _GFi. Among the FOSs produced were kestose, nystose, 1-fructofuranosyl-nystose, and potentially a novel trisaccharide produced by this strain. To reduce the content of mono- and disaccharides in the mixture, run a successive fermentation was run with two Saccharomyces cerevisiae strains. Fermentations run with S. cerevisiae S227 improved FOS purity in the mixture from 39 ± 3% to 61.0 ± 0.6% (w/w) after 16 h of fermentation. This study showed that agro-industrial wastes such as molasses with aguamiel are excellent alternatives as substrate sources for the production of prebiotic FOS, resulting in a lower-cost process.

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.

Enzymatic Synthesis of the Fructosyl Derivative of Sorbitol

The aim of the study was to determine the effect of selected reaction parameters—temperature (37–57 °C), pH (5.8–7.9), substrates ratio (sucrose/sorbitol 0.5/1.5 to 1.5:0.5 (m/m)), and the presence of NaCl—on the course of fructosyl-sorbitol synthesis with an enzyme preparation (11 760 U/100 g of sucrose) containing fructosyltransferase and β-d-fructofuranosidase from Aspergillus niger. A mixture of at least three fructosyl sorbitol derivatives was obtained: two mono-fructosyl and one di-fructosyl. The highest content of all sorbitol derivatives combined was 2.7 g/100 mL for pH 6.8–6.9, and the sucrose/sorbitol ratio was 1:1. Increasing the reaction temperature from 37 to 57 °C reduced the time required to reach the maximum product content from 5 to 2 h, while the concentration did not increase. The addition of NaCl (0.63 M) extended the reaction time from 2 to 5 h and slightly lowered the maximum concentration of sorbitol derivatives (from 2.74 to 2.6 g/100 mL).

Safety assessment of β-fructofuranosidase from Aspergillus brunneoviolaceus

β-Fructofuranosidase (β-D-fructofuranoside fructohydrolase; EC 3.2.1.26) is used in the production of fructo-oligosaccharides that are commonly used by the food industry as prebiotics for their purported health benefits. The β-fructofuranosidase discussed herein is obtained from a novel source organism that is a non-genetically modified strain of Aspergillus brunneoviolaceus, which phylogenetically belongs to the Aspergillus section Nigri. The safety of β-fructofuranosidase was evaluated in a series of toxicology studies as prescribed by Tier 1 toxicity testing by the European Food Safety Authority, including an evaluation of the mutagenicity and genotoxicity potential using the in vitro bacterial reverse mutation and mammalian chromosomal aberration assays, as well as systemic toxicity in a 90-day oral subchronic toxicity study in Sprague-Dawley rats. β-Fructofuranosidase was demonstrated to lack mutagenic or genotoxic potential based on the results of the in vitro assays due to absence of increased revertant colonies in the bacterial reverse mutation test and incidence of chromosome aberrations in the chromosomal aberration assay. Administration of β-fructofuranosidase by gavage at doses up to 1200 mg total organic solids (TOS)/kg body weight/day for 90 days did not elicit any systemic toxic effects in rats based on a lack of adverse effect in any study parameter, and therefore the no-observed-adverse-effect level of β-fructofuranosidase was concluded to be 1200 mg TOS/kg body weight/day, the highest dose tested. The results of the toxicology studies on β-fructofuranosidase from A. brunneoviolaceus demonstrate this species to be a safe and suitable source of enzymes for use by the food industry.

Integrated Ultrasonication and Microbubble-Assisted Enzymatic Synthesis of Fructooligosaccharides from Brown Sugar

Fructooligosaccharides (FOS) are considered prebiotics and have been widely used in various food industries as additives. Ultrasonication has been widely used to enhance food processes; however, there are few reports on ultrasound-assisted FOS synthesis. In the present study, FOS were produced from brown sugar using ultrasonication combined with microbubbles, and the production was optimised using a Box-Behnken experimental design. Here we showed that a combination of ultrasonication and microbubbles could boost the enzyme activity by 366%, and the reaction time was shortened by 60%. The reaction time was a significant variable affecting the FOS production. The optimum conditions were 5 min 45 s of ultrasonication and 7 min 19 s of microbubbles with a reaction time of 5 h 40 min. The maximum enzyme activity and total FOS yield were 102.51 ± 4.69 U·mL^-1 and 494.89 ± 19.98 mg·g^-1 substrate, respectively. In an enlarged production scale up to 5 L, FOS yields were slightly decreased, but the reaction time was decreased to 4 h. Hence, this technique offers a simple and useful tool for enhancing enzyme activity and reducing reaction time. We have developed a pilot technique as a convenient starting point for enhancing enzyme activity of oligosaccharide production from brown sugar.