1-FFT amino acids involved in high DP inulin accumulation in Viguiera discolor

Production, modification and degradation of fructans and fructooligosacharides by enzymes originated from plants

Non-starch polysaccharides exhibit numerous beneficial health effects but compounds belonging to FODMAP (Fermentable Oligo- Di- and Monosaccharides and Polyols) has been recently connected to several gastrointestinal disorders. This review presents integrated literature data on the occurrence and types of fructans and fructooligosaccharids (classified as FODMAPs) as well as their degrading enzymes present in plants. Plants from the family Asteraceae and many monocotyledones, including families Poaceae and Liliaceae, are the most abundant sources of both fructans and fructan-degrading enzymes. So far, vast majority of publications concerning the application of these specific plants in production of bakery products is related to increase of dietary fibre content in these products. However, there is limited research on their effect on FODMAP content and fibre balance. The authors emphasize the possibility of application of enzyme rich plant extract in food production casting light on the new scientific approach to fibre modification.

Strategic biomodification for raw plant-based pretreatment biorefining toward sustainable chemistry

Plant-based pretreatment biorefining is the initial triggering process in biomass-conversion to bio-based chemical products. In view of chemical sustainability, the raw plant-based pretreatment biorefining process is more favorable than the fossil-based one. Its direct use contributes to reducing CO2 emissions and the production cost of the target products by eliminating costly steps, such as the separation and purification of intermediates. Three types of feedstock plant resources have been utilized as raw plant feedstock sources, such as: lignocellulosic, starchy, and inulin-rich feedstock plants. These plant sources can be directly used for bio-based chemical products. To enhance the efficiency of their pretreatment biorefining process, well-designed biomodification schemes are discussed in this review to afford important information on useful biomodification approaches. For lignocellulosic feedstock plants, the enzymes and regulatory elements involved in lignin reduction are discussed using: COMT, GAUT4, CSE, PvMYB4 repressor, etc. For inulin-rich feedstock plants, 1-SST, 1-FFT, 1-FEH, and endoinulinase are illustrated in relation with the reduction of chain length of inulin polymer. For starchy feedstock plants, their biomodification is targeted to enhancing the depolymerization efficiency of starch to glucose monomer units. For this biomodification target, six candidates are discussed. These are SBE I, SBE IIa, SBE IIb, GBSS I, PTSTI, GWD 1, and PTSTI. The biomodification strategies discussed here promise to be conducive to enhancing the efficiency of the plant-based pretreatment biorefining process.

A novel chicory fructanase can degrade common microbial fructan product profiles and displays positive cooperativity

Fructan metabolism in bacteria and plants relies on fructosyltransferases and fructanases. Plant fructanases (fructan exohydrolase, FEH) only hydrolyse terminal fructose residues. Levan (β-2,6 linkages) is the most abundant fructan type in bacteria. Dicot fructan accumulators, such as chicory (Cichorium intybus), accumulate inulin (β-2,1 linkages), harbouring several 1-FEH isoforms for their degradation. Here, a novel chicory fructanase with high affinity for levan was characterized, providing evidence that such enzymes widely occur in higher plants. It is adapted to common microbial fructan profiles, but has low affinity towards chicory inulin, in line with a function in trimming of microbial fructans in the extracellular environment. Docking experiments indicate the importance of an N-glycosylation site close to the active site for substrate specificity. Optimal pH and temperature for levan hydrolysis are 5.0 and 43.7 °C, respectively. Docking experiments suggested multiple substrate binding sites and levan-mediated enzyme dimerization, explaining the observed positive cooperativity. Alignments show a single amino acid shift in the position of a conserved DXX(R/K) couple, typical for sucrose binding in cell wall invertases. A possible involvement of plant fructanases in levan trimming is discussed, in line with the emerging 'fructan detour' concepts, suggesting that levan oligosaccharides act as signalling entities during plant-microbial interactions.

Conversion of inulin-rich raw plant biomass to 2,5-furandicarboxylic acid (FDCA): Progress and challenge towards biorenewable plastics

The current commercial plastic manufactures have been produced using petroleum-based resource. However, due to concerns over the resource depletion and the environmental sustainability, bioresource-based manufacturing processes have been developed to cope against these concerns. Bioresource-derived 2,5-furandicarboxylic acid (FDCA) can be utilized as a building block material for plastic manufactures. To date, numerous technologies have been developed for the production of FDCA using various types of bio-based feedstocks such as hydroxymethylfurfural (HMF), 6-C sugars, and polysaccharides. The commercial companies produce FDCA using HMF-based production processes due to their high production efficiency, but the high price of HMF is a problem bottleneck. Our review affords important information on breakthrough approaches for the cost-efficient and sustainable production of FDCA using raw plant feedstocks rich in inulin. These approaches include bioprocessing technology based on the direct use of raw plant feedstocks and biomodification of the target plant sources. For the former, an ionic liquid-based processing system is proposed for efficient pretreatment of raw plant feedstocks. For the latter, the genes encoding the key enzymes; sucrose:sucrose 1-fructoyltransferase (1-SST), fructan:fructan 1-fryuctosyltransferase (1-FFT), fructan 1-exohydrolase (1-FEH), and microbe-derived endoinulinase, are introduced for biomodification conducive to facilitating bioprocess and improving inulin content. These approaches would contribute to cost-efficiently and sustainably producing bio-based FDCA.

A Fructan Exohydrolase from Maize Degrades Both Inulin and Levan and Co-Exists with 1-Kestotriose in Maize

Enzymes with fructan exohydrolase (FEH) activity are present not only in fructan-synthesizing species but also in non-fructan plants. This has led to speculation about their functions in non-fructan species. Here, a cell wall invertase-related Zm-6&1-FEH2 with no "classical" invertase motif was identified in maize. Following heterologous expression in Pichia pastoris and in Nicotiana benthamiana leaves, the enzyme activity of recombinant Zm-6&1-FEH2 displays substrate specificity with respect to inulin and levan. Subcellular localization showed Zm-6&1-FEH2 exclusively localized in the apoplast, and its expression profile was strongly dependent on plant development and in response to drought and abscisic acid. Furthermore, formation of 1-kestotriose, an oligofructan, was detected in vivo and in vitro and could be hydrolyzed by Zm-6&1-FEH2. In summary, these results support that Zm-6&1-FEH2 enzyme from maize can degrade both inulin-type and levan-type fructans, and the implications of the co-existence of Zm-6&1-FEH2 and 1-kestotriose are discussed.

Fructans as Immunomodulatory and Antiviral Agents: The Case of Echinacea

Throughout history, medicinal purposes of plants have been studied, documented, and acknowledged as an integral part of human healthcare systems. The development of modern medicine still relies largely on this historical knowledge of the use and preparation of plants and their extracts. Further research into the human microbiome highlights the interaction between immunomodulatory responses and plant-derived, prebiotic compounds. One such group of compounds includes the inulin-type fructans (ITFs), which may also act as signaling molecules and antioxidants. These multifunctional compounds occur in a small proportion of plants, many of which have recognized medicinal properties. Echinacea is a well-known medicinal plant and products derived from it are sold globally for its cold- and flu-preventative and general health-promoting properties. Despite the well-documented phytochemical profile of Echinacea plants and products, little research has looked into the possible role of ITFs in these products. This review aims to highlight the occurrence of ITFs in Echinacea derived formulations and the potential role they play in immunomodulation.

The fructan syndrome: Evolutionary aspects and common themes among plants and microbes

Fructans are multifunctional fructose-based water soluble carbohydrates found in all biological kingdoms but not in animals. Most research has focused on plant and microbial fructans and has received a growing interest because of their practical applications. Nevertheless, the origin of fructan production, the so-called "fructan syndrome," is still unknown. Why fructans only occur in a limited number of plant and microbial species remains unclear. In this review, we provide an overview of plant and microbial fructan research with a focus on fructans as an adaptation to the environment and their role in (a)biotic stress tolerance. The taxonomical and biogeographical distribution of fructans in both kingdoms is discussed and linked (where possible) to environmental factors. Overall, the fructan syndrome may be related to water scarcity and differences in physicochemical properties, for instance, water retaining characteristics, at least partially explain why different fructan types with different branching levels are found in different species. Although a close correlation between environmental stresses and fructan production is quite clear in plants, this link seems to be missing in microbes. We hypothesize that this can be at least partially explained by differential evolutionary timeframes for plants and microbes, combined with potential redundancy effects.