Oligosaccharides from Coprophilous fungi: An emerging functional food with potential health-promoting properties: a recent appraisal

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, high production costs, etc. 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 & 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.

from the herbivore rumen due to their incomplete digestion and consequently microbes on dung use them up. The array of enzymes in the rumen is not only from gut microbial diversity but also from the multiplicity of fibrolytic enzymes produced by individual microbes [49].
Recently, from our laboratory, sixty-one autochthonous coprophilous fungal strains were screened for the ability to biotransform sucrose and inulin into FOS and IOS by producing fructosyltransferase and inulinase, respectively. The isolates exhibited high transfructosylating activity and produced short-chain FOSs including GF3, GF4, and GF5. Coprophilous fungus isolate XOPB-48 identified as Aspergillus niger showed a robust combination of high extracellular transferase activity following HPLC-RI analysis [50]. The enzyme exhibited a good transfructosylating activity by catalyzing sucrose to FOS with an I/S ratio of 1.77. The utilization of herbivore dung as a cheap and readily available bioresource raw material allows the development of low-cost bioprocess for FOS and IOS production. In addition, the complex carbohydrate and bioactive characteristics of cellulose and lignin in dung biomass, therefore, displays unexplored reservoir as it can produce substrates with transfructosylating activity.

Oligosaccharides
Oligosaccharides form part of new functional food with great potential to improve health due to their physicochemical characteristics [51]. They are classified as glycosides since they contain 3-10 sugars moieties [52]. Oligosaccharides are carbohydrates with low molecular weight and low DP [51]. Carbohydrates are the main group that forms oligosaccharides; their monosaccharide units include glucose, galactose, fructose, and xylose. The non-digestible oligosaccharides emanate from the survey that carbon atoms of the monosaccharides have some disposition that make osidic bonds non-digestible to hydrolytic activity of enzymes in the human intestine [53].
Oligosaccharide stability differs according to classes depending on sugar residues present and anomeric configuration [54]. Predominantly, β-linkages are stronger and stable than α-linkages, and hexoses are more strongly linked than pentoses [55]. They also have high moisture retaining capability, preventing excessive drying, and low water activity that inhibits microbial contamination [56]. 7

Physicochemical and functional properties of oligosaccharides
Oligosaccharides have biofunctional and physicochemical properties that make them desirable for consumption as food ingredients or supplements [51]. Incorporation of oligosaccharides enriches the rheological and physiological characteristics of foods [57]. This is predominantly due to their water solubility and sweetness. Oligosaccharides are slightly sweeter than sucrose (0.3-0.6 times), but the sweetness is dependent on the DP, chemical array, and level of mono-and disaccharide present in the mixture [56]. The viscosity of fructooligosaccharide (FOS) solution is relatively higher than that of mono-and disaccharide (sucrose) at the same concentration [31].
They are more viscous due to their higher molecular weight [58]. They alter the amount of browning in food by recasting the freezing temperature of some foods. They control microbial contamination by absorbing water since they act as a drying agent due to their moisture-retaining capability [59]. FOSs have higher thermal stability than sucrose; they are stable within the normal pH range of foods (pH 4.0-7.0) [27]. Their stability is dependent on ring form, sugar residue content, anomeric configuration, and linkage type. Principally β-linkages are stronger compared to α-linkages while hexoses are strongly linked than pentoses [58].
Oligosaccharides are used as low cariogenic sugar substitutes, as they are inactivated by mouth enzymes or in the upper gastrointestinal tract to form acid or polyglucans due to their physicochemical characteristics of being less sweet, making them suitable for consumption by diabetics [60,61]. They show immoderately high structural diversity than oligonucleotides and oligopeptides [62].
FOS can be produced using three methods: extraction from inulin-rich plant material, enzymatic synthesis of sucrose, or degradation of inulin by enzyme hydrolysis [68][69][70]. However, the majority of FOS, which are food ingredients are synthesized through enzymatic degradation of inulin from plant polysaccharides or synthesized from sucrose by fructosyltransferase activity [71]. FOS is synthesized by a wide array of enzymes such as inulinases and fructosyltransferases in large-scale industrial production [72,73]. The various microbial and plant sources of FOS are tabulated in Table 2.  [101]. Numerous advantages have been associated with SSF. These include simplicity in operation, which produces high-level products after fermentation [102]. SSF uses low water consumption; requires less sterilization and permits little/no microbial contamination during product formation. In addition, it requires less capital to operate, as it uses simple equipment, less space, and agro-industrial residues as substrates that are converted to bulk chemicals with high volumetric products of high commercial value [31,103]. The downstream process is easier with reduced stirring and low sterilization. However, there are also drawbacks associated with solid-state fermentation. These include the build-up of temperature, pH, moisture, and substrate concentrations. Since it uses little water, it becomes difficult to control [84].
Moreover, the particle size of the substrate is a variable factor that presents a strong effect during the fermentation process. Since small particle increases surface area between the gas phase and microbes, they can influence the medium by making water and oxygen transfer of nutrients difficult [104]. Furthermore, media optimization is labour intensive and time-consuming for higher yields of FOS [105].

Inulooligosaccharides production from inulin hydrolysis
With the increasing demand for nutritional food, significant attention is being paid to functional foods. Aside from the basic nutrition, the functionality of food with high production value and nutraceutical effect is in great demand [21,106]. These predominant reasons have led to the production of IOS, which is a class of prebiotic. Overwhelming consumer consciousness for healthier food has heightened the fast growth of the functional food market for IOS [107].
Inulin as a substrate can be regarded as a promising source for inulooligosaccharide production [108]. IOSs produced from inulin hydrolysis are reported to have homogeneous biochemical and physiological functions [109,110]. Inulin with high DP has shown good prebiotic potential [108,111]. This is due to its resistance to digestion by the gut enzymes because of the presence of fructose in their β-configuration [112]. However, the DP varies from different plant species, age of plant, climatic conditions, harvesting periods, and inulin-rich plant organic material [108]. Streptococcus mutans to form acids and β-glucan, which is insoluble and a major cause of dental caries [70]. Fourth, inulin-type fructans act as prebiotics since they promote the growth of Bifidobacteria while concomitantly suppressing the growth of potentially putrefactive microbes in the digestive tract [21, 119]. These properties improve gut functions. The evaluation of gut microflora before and after inulin intakes is illustrated in Fig. 6.

Enzyme-mediated production of inulooligosaccharides and fructooligosaccharides
Complex carbohydrates are difficult to synthesize hence require alternative methods that can degrade polysaccharides to maximize yields. Inulin hydrolysis has been employed in the production of syrup with high fructose concentration [107]. The reaction was carried out using an acid catalyst and was found to present several shortcomings including high processing temperature, leading to high energy consumption, inulin precipitation, and microbial contamination [120]. In addition, by-products with no sweetening capabilities, resulting in overall decrease in yields were also reported. Several other drawbacks on chemical hydrolysis include extended time for refluxing, found to require acid-resistant equipment [21]. Moreover, the processes are tedious, as they involve protection, deprotection, and activation strategies to control the stereochemistry and regioselectivity of the resulting oligosaccharide, which is undesirable and unrealistic for large-scale production [121,122]. In addition, the chemical method requires the use of hazardous & expensive chemicals and results in low yields and high production costs. Due to the aforementioned challenges, the application of microbial enzymes for oligosaccharide production is recognized as an attractive strategy [27,123].
Application of enzyme-based approach for catalytic production of oligosaccharides has been applied as an alternative technique to acid and chemical hydrolysis due to its simplicity in preparation, rapidity, and reproducibility in mild reaction conditions and easy separation of products

Enzymes used for oligosaccharides' production
Fructoligosaccharide is produced by the transfer of fructose residues to sucrose molecules by the Predominantly, Aspergillus species have received particular interest in microbial FOS production [140,141]. Aspergillus niger and Aspergillus oryzae have been exploited for enzyme production since they have GRAS status [132]. Other fungi such as Penicillium rugulosum and Aspergillus phoenicis CBS 294.80, which secrete a thermostable inulinase for industrial fructose production also produce a sucrose-1 F -fructosyltransferase, SFT (E.C 2.4.1.99) [142,143]. Fungal ftases have been the focal point, as numerous studies on industrial biotechnology have described the isolation and screening of intra or extracellular fructosyltransferase [133,144]. Aspergillus japonicus with other moulds was selected after a screening exercise for the ability to produce transferase [145].
In addition, Madlov et al. (2000) selected Aspergillus pullulans and Aspergillus niger for their potential to produce fructosyltransferase [146]. Furthermore, Fernandez et al. (2007) screened seventeen filamentous fungi grown in batch cultures and compared their ability to produce βfructofuranosidase and fructosyltransferase [147]. The findings revealed three strains of Aspergillus niger ATTC 20611, IPT-615 and Aspergillus oryzae IPT-301 as good candidates for industrial fructosyltransferase production.
Screening of new fungal isolates is always a difficult procedure due to a number of evaluations.
However, numerous reports still exist on screening fungi for biotechnological application. A presumptive and indirect colorimetric plate assay was employed for screening of a filamentous fungus for transfructosylation ability [148]. The method was carried out to determine the simultaneous release of fructose and glucose from sucrose biotransformation. A glucose oxidaseperoxidase reaction using phenol and 4-aminoantipyrine was used for glucose determination.
Fructose dehydrogenase oxidation in the presence of tetrazolium salt was used for fructose determination. The formation of a pink halo revealed the presence of glucose while blue halo formation confirmed the presence of fructose and transfructosylation activity. Other studies on screening fungal and yeast species for fructosyltransferase production have also been reported, as they are a more feasible and economic source of biocatalytic enzymes [18,87,[149][150][151]. Based on these evaluations, fungal fructosyltransferase is more desirable than plant and bacterial fructosyltransferase for large-scale production of FOS. This is due to their physicochemical characteristics including minimal loss of enzyme activity, by-product inhibition, and low molecular weight, which allows easier separation of the biocatalyst from the product.

Bacterial fructosyltransferases
FOS-producing enzymes are rarely secreted among bacterial species, but notwithstanding some strains of bacteria have been reported to be inulinase producers [31]. A study by Hicke et al. (1999) reported Streptococcus mutans as the only known source of bacterial inulinase [152]. In earlier studies, cloning and sequencing of the β-D-fructosyltransferase was reported from Streptococcus salivarius. The recombinant fructosyltransferase was expressed in Escherichia coli and later purified to homogeneity [153]. The enzyme catalysed the transfer of fructosyl moiety of sucrose to multiple receptors including glucose, water, and unhydrolysed sucrose via the Ping Pong mechanism of fructosyl-enzyme intermediate [154,155]. A transfructosylating enzyme from Bacillus macerans EG-6 produced FOS with a yield of 33% in the presence of 50% sucrose as substrate [80]. A novel strain of Bacillus licheniformis was reported to be capable of producing FOS and a polysaccharide-type levan [156,157]. An ethanol-producing bacteria strain of Zymomonas mobilis has been reported to produce levansucrase, capable of producing FOS and levan [158]. Levansucrases are fructosyltransferases belonging to the family 68 of glycoside hydrolases, which catalyzes FOS formation and synthesis of β-(2,6) levan [156]. In this study, extracellular levansucrase along with levan as the supernatant was used as biocatalyst in FOS sugar syrup. FOS yield of 24-34% was obtained, comprising of 1-kestose, 6-kestose, neokestose and nystose [31]. Glucose which formed as a by-product during FOS production was found to inhibit transfructosylation reaction along with ethanol (7%) in sucrose syrup [159]. The fructan syrup group showed prebiotic characteristics. In another study, a strain of Lactobacillus reutri 121 was reported to produce 10 g/L FOS (95% 1-kestose and 5% nystose) in the supernatant when grown on sucrose medium as a carbon source. Fructosyltransferase obtained from the strain when incubated at 17 h with sucrose also produced FOS and 0.8 g/l inulin [160,161].
Furthermore, the effect of ten commercially available oligosaccharides was tested in vitro on the

Microbial exoinulinases
Inulin is a polyfructan containing linear β-2,1 linked polyfructose chain and is considered to be the most suitable substrate for enzyme production [129]. It is also considered as a renewable source of raw material in fructose syrup manufacturing and FOS production [162]. It is insoluble in water due to variations in chain length elongation and molecular weight, which varies between 3500 -5500. Microbial inulinase (2,1-β-D-fructan fructohydrolase EC, 3

Potential health benefits of oligosaccharides Prebiotics
Prebiotics are biofunctional food supplements that stimulate selective growth of Lactobacilli and Bifidobacteria in the gut, leading to improved health [166]. Prebiotics creates an unfavourable environment for harmful invasive pathogens by stimulating Lactobacilli and Bifidobacteria proliferation [167]. The intestinal bacteria ferment oligosaccharides and produce large compounds of short-chain fatty acid, resulting in acidic conditions in the colon which colonize adhesive sites and secrete bacteriostatic peptides [168]. The prebiotics bacteria survive harsh acidic conditions and are adherent to mucosal walls of the gut by producing organic acids like lactic acid, which are inhibitors of many pathogenic microbes hence improving gut health [169].
Some of the major prebiotic functions are illustrated in Fig. 7.

Dietary fiber effect
Dietary fibers are plant or carbohydrates analogous that are not easily hydrolyzed in the upper part of the small intestines [170]. They contain edible plant polysaccharides remnants that cannot be easily hydrolyzed by human digestive enzymes (AACC Report 2001). The partial or complete fermentation in the large bowel is crucial in the metabolism of dietary fiber [170]. There is increasing evidence that supplementation of diet with fermentable fiber alters the gut function and structure either by modification or production of gut-derived hormones, which improve glucose homeostasis [171]. It is for this reason that oligosaccharides are associated as part of its promoters as a result of food metabolism [173]. In the gut, there exist two types of fermentation after ingestion of food proteolytic and saccharolytic enzymes. The latter is more favorable due to metabolic by-products formed such as acetate, SCFAs, propionate, and butyrate [174]. When a model system of the human gut was investigated after feeding of galactooligosaccharides, there was a considerable depreciation of nitroreductase, a metabolic activator and carcinogenic substance that decreases indole and isovaleric levels [15]. According to studies done by Kim et al induce an anti-inflammatory effect on colon cancer cells [175]. Another study reported the effect of starch administration on human flora-associated rats (HFA), where there was a decrease in ammonia levels and β-glucuronidase with high-level caecal butyrate observed. Butyrate which is critical for cancer reduction is not only the primary energy source for colonocytes but also helps to maintain a healthy epithelium. It can also play a large part in cancer prevention. Such interactions include activation of apoptosis, a mechanism that is inactivated in cancer cells that would normally contribute to their death and an increase in the immunogenicity of cancer cells due to an increase in the expression of proteins on the cell surface [176]. Butyrate plays a dual role of maintaining a healthy epithelium as well provides energy for colonocytes [15].
Furthermore, decrease in azomethane-induced colorectal cancer in F344 rats when fed on oligofructose diet indicates anti-cancer potential of the functional food [23].

Mineral absorption
To expand the knowledge of oligosaccharides in improving mineral absorption, several mechanisms have been explained. The consumption of oligosaccharides has been explained in several experimental animals [177,178]. Moreover, there was a significant increase in calcium absorption if there was a combination of the two [179]. Bioavailability of oligosaccharides occurs largely in the colon; this is due to fermentation by commensal microbes [180]. SCFAs decrease luminal pH, leading to an acidic environment favouring solubility of Ca 2+ , Mg 2+ , Fe 2+ that maintain a homeostatic balance between Fe 2+ and Zn 2+ [84,181]. In another study, gastrectomized experimental animals were fed with oligosaccharides. The iron uptake was found to increase, suggesting the significance of the functional food in alleviating anaemic conditions. Oligosaccharides uptake was also observed to prevent osteopenia in rats, as calcium ions stored in bones was easily absorbed [23]. Numerous benefits emanate from intestinal calcium and magnesium uptake [6].

Lipid metabolism
Animal studies carried out in mice showed that oligofructan, inulin and non-digestible (but fermentable) oligomer of β-D-fructose (obtained by inulin hydrolysis) possess the physiological effect on cholesterol while significantly lower serum triglyceride levels by decreasing postprandial cholesterolemia and triglyceridemia by 15% and 50%, respectively [182]. The lipogenic decline in enzyme activity and very-low-density lipoprotein (VLDL), which contains the highest amounts of triglycerides particles contribute to this effect [183]. Moreover, FOS fermentation increases propionic acid in intestinal mucosa and in turn reduces levels of triacylglycerol (TAG) and associated hypercholesterolemia LDL and VLDL [23]. In human studies, the use of inulin and oligofructose as food supplements in normal and hyperlipidaemic conditions showed no effects on serum cholesterol or triglyceride. However, three investigations showed slight reduction in triacylglycerol, while four inspections cholesterol and triacylglycerol lowered significantly [114,184]. Inulin appears to be more suitable than oligofructose in reducing triglyceridemia while in animal studies, both oligofructose and inulin were equally active [185]. Based on these findings, prebiotics have been shown to affect hepatic lipid metabolism [185]. In a study of diabetic rats, simple carbohydrates were replaced with XOS in their diets and there was a drastic drop in serum cholesterol and TAG in diabetic rats while liver triacylglycerol increased to commensurate levels to that observed in healthy rats [186]. This was attributed to lipogenic enzyme inhibition, resulting from prebiotic fermentation in the gut by the action of propionate [15].

Defense mechanism and immune regulation
Consumption of functional food boosts the immune system [170]. Fermentation of saccharolytic metabolites, resulting from dietary intake is closely associated to be in contact with gut lymphoid tissues which cover the majority of the intestinal immune system [166,170]. Products of FOS fermentation may modulate the GALT as well as the systemic immune system [171]. A concept of immunity suggested by Saad et al. (2013) showed that innate immune response can be activated by sugar moieties interacting synergistically with innate receptors on the host plasma membrane in dendritic cells and macrophages [185]. Β-glucose oligosaccharide activates immune reactions by binding to macrophages receptors. Orally ingested oligofructose and inulin modulate immune system parameters such as IL-10 and IFN-γ natural killer cells activity, lymphocyte proliferation, intestinal IgA, and increase polymeric immunoglobulin receptor expression in ileum and colon regulation [170]. Consumption of prebiotics fiber induces bifidogenic microflora as a result of short-chain fatty acid from fiber fermentation and direct contact with cytoplasmic components with immune cells [185].

Antioxidant effect
Antioxidants are natural or synthetic compounds that may delay or prevent oxidative stress caused by physiological oxidants [50]. Conventionally, the antioxidants are divided into two groups: the antioxidants that scavenge directly for active free radicals such as reactive oxygen species (ROS) or reactive nitrogen species (RNS), and antioxidants that inhibit oxidative stress [151,187]. Free radicals are customarily unsteady and originate from nitrogen (RNS), oxygen (ROS) and, sulfur (Reactive Sulphur Species: RSS) [188]. ROS, RNS, and RSS generation in radical and/or non-radical forms occur in humans and animal cells because of metabolic and physiological processes [189]. Moreover, ROS-induced free radicals from exogenous or endogenous sources can be injurious to the body cell biomolecules, causing impairment to cell functions and oxidative stress or apoptosis [190]. Free radicals have also been implicated in numerous pathologies including cardiovascular complications, neurodegenerative disorders as well as oncogenic complications [191].
Intake of inulin-type oligosaccharides, vitamin C, vitamin E, and carotenoids have been found to have the potential to minimize the harmful effects of reactive species [188]. Dietary intake of antioxidants such as tocopherol, carotenoids, and ascorbate are difficult to disentangle through epidemiological studies from other vital vitamins and ingredients in fruits and vegetables.
Nevertheless, several studies published suggest that antioxidants are a major remedy for endogenous damage to DNA, lipids, and proteins [189,192]. Antioxidants play a key role in immune system activation by causing the proliferation of B and T cells, natural killer cells, and lymphokine-activated killer cells that prevent the body defense mechanism from pathogens [193].
Supplementation with dietary antioxidants counteracts the oxidants thereby boosting the complement system [50].

Antioxidants and cardiovascular disease
Cardiovascular complications are associated with low concentrations of ascorbate, tocopherol, and β-carotene [194]. From cardiovascular studies, oxidative modifications of apolipoproteins B 100 play a key role in the recognition of low-density lipoprotein (LDL). LDL uptake by macrophage receptors leads to foam cell formation and atherosclerotic plaques [195]. Lipid peroxidation has been found to alter reactive products of apolipoprotein B 100, leading to a decrease in net charge, a modification that leads to its recognition by scavenger receptors [196].
Antioxidants have anticancer effects. During cell division, an unpaired lesion of DNA can lead to mutation. Hence, an overriding factor in mutagenesis and carcinogenesis occurs from continuous cell division which is a precursor of tumour cells [197]. An increase in cell division enhances mutagenesis. It is difficult for cancer to emerge in non-dividing cells. Antioxidant intake can decrease carcinogenesis and mutagenesis in two ways: by decreasing oxidative DNA damage and by decreasing cell division [193].

Antioxidants and cataracts
Most common ophthalmology procedures involve cataract removal. Taylor and Allen (1992) investigated the impressive evidence that cataracts have oxidative etiology and dietary antioxidants can prevent their formation in humans [198]. Findings from five epidemiological studies assessed the effect of dietary antioxidants on cataracts and showed the deterrent effect of ascorbate, tocopherol, and carotenoids. Those individuals placed on tocopherol or ascorbate supplements daily active ingredient vitamin E succinate (VES)-grafted-chitosan oligosaccharide had about one-third risk of developing cataracts [199][200][201][202][203]. Other factors causing oxidative stress include cigarette smoking and radiation [204]. The eye protein shows an increased level of methionine sulfoxide, and more than 60% oxidation occurs on methionine residues, causing cataracts. Decrease or abstinence from smoking and increase in dietary consumption of antioxidants is a promising strategy to reduce cataracts.
Various experimental models have been used to analyse the antioxidant potential of free radical scavengers and inhibitors. These models include 1,1-diphenyl-2-picrylhydrazyl (DPPH) method, which is used to evaluate the free radical scavenging ability of natural antioxidants in food and beverages [151,205,206]. Ferric reducing antioxidant power assay (FRAP) is based on the reduction of Fe 3+ -TPTZ complex to the ferrous form at low pH. This reduction is monitored by measuring the absorption spectrophotometrically at 593 nm [207,208]. Moreover, Ojwach et al. The inducible nitric oxide synthase enzyme (iNOS) synthesizes NO and the enzyme has been widely characterized to be an inducer of both chronic and acute inflammation [209]. Other assays described also include 2,2-azinobis (3-ethylbenzothiazoline 6-sulfonate) 2,2'-axino-bis-3ethylbenzothiazoline-6-sulfonic acid (ABTS), oxygen radical absorption capacity assay (ORAC) [210].

Other applications
Fructoligosaccharides employability as functional foods has led to their industrial applications in the food and beverage industry. In beverages, they are used in cocoa, fruit drinks, infant formulas and powdered milk as supplements [88, 166,177]. In addition, these functional foods are used as probiotics in yoghurt and other milk products to create symbiotic products. Other current applications include puddings and sherbets, desserts such as jellies, confectioneries (chocolate), biscuits, pastries spread (jam), marmalades, and meat products such as fish paste and tofu [56, 211].

Conclusions and future direction
Biofunctional properties and health benefits of oligosaccharides have increased the importance of bioprospecting for novel, cheap and renewable bioresources for their production. FOS are synthesized in vitro from precursors such as sucrose using fructosyltransferase secreted by coprophilous fungi. Furthermore, IOS can also be produced from the enzymatic hydrolysis of inulin under controlled conditions. However, the main drawback of the production process is low