Lignocellulose derived functional oligosaccharides: production, properties, and health benefits

Pichia pastoris Mediated Digestion of Water-Soluble Polysaccharides from Cress Seed Mucilage Produces Potent Antidiabetic Oligosaccharides

Diabetes mellitus is a heterogeneous metabolic disorder that poses significant health and economic challenges across the globe. Polysaccharides, found abundantly in edible plants, hold promise for managing diabetes by reducing blood glucose levels (BGL) and insulin resistance. However, most of these polysaccharides cannot be digested or absorbed directly by the human body. Here we report the production of antidiabetic oligosaccharides from cress seed mucilage polysaccharides using yeast fermentation. The water-soluble polysaccharides extracted from cress seed mucilage were precipitated using 75% ethanol and fermented with Pichia pastoris for different time intervals. The digested saccharides were fractionated through gel permeation chromatography using a Bio Gel P-10 column. Structural analysis of the oligosaccharide fractions revealed the presence of galacturonic acid, rhamnose, glucuronic acid, glucose and arabinose. Oligosaccharide fractions exhibited the potential to inhibit α-amylase and α-glucosidase enzymes in a dose-dependent manner in vitro. The fraction DF73 exhibited strong inhibitory activity against α-amylase with IC50 values of 38.2 ± 1.12 µg/mL, compared to the positive control, acarbose, having an IC50 value of 29.18 ± 1.76 µg/mL. Similarly, DF72 and DF73 showed the highest inhibition of α-glucosidase, with IC50 values of 9.26 ± 2.68 and 50.47 ± 5.18 µg/mL, respectively. In in vivo assays in streptozotocin (STZ)-induced diabetic mice, these oligosaccharides significantly reduced BGL and improved lipid profiles compared to the reference drug metformin. Histopathological observations of mouse livers indicated the cytoprotective effects of these sugars. Taken together, our results suggest that oligosaccharides produced through microbial digestion of polysaccharides extracted from cress seed mucilage have the potential to reduce blood glucose levels, possibly through inhibition of carbohydrate-digesting enzymes and regulation of the various signaling pathways.

Xylooligosaccharides from lignocellulosic biomass and their applications as nutraceuticals: a review on their production, purification, and characterization

Xylooligosaccharides (XOS) are considered a potent source of prebiotics for humans. The global prebiotic market is expanding in size, was valued at USD 6.05 billion in 2021, and is expected to grow at a 14.9% compound annual growth rate between 2022 and 2030, indicating a huge demand. These XOS are non-digestible pentose sugar oligomers comprising mainly xylose. Xylose is naturally present in the lignocellulosic biomass (LCB), fruits and vegetables. Apart from the prebiotic effect, these XOS have been reported to reduce blood cholesterol, possess antioxidant effects, increase calcium absorption, reduce colon cancer risk, and benefit diabetic patients. The primary use of XOS is reported in the feed industry followed by health, medical use, food and drinks. LCB mainly contains glucan, xylan and lignin. After glucan, xylan is the second-highest available sugar on the globe composed of xylose. Therefore, the xylan fraction of LCB has great significance in producing food, feed and energy. Glucan has been exploited for the commercial production of ethanol, xylitol, furfural, hydroxymethyl furfural and glucose. As of now, xylan has limited applications. Therefore, xylan can be exploited to convert to XOS. The production of XOS from LCB fraction not only helps to produce these at a very low price, but also helps in the reduction of greenhouse gases. Its use in food and drinks is increasing as it can be derived from the abundantly and cheaply available LCB. The article provides a review on the production, purification and characterization of XOS in view of their use as nutraceuticals. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Sustainable production of cellulose and hemicellulose-derived oligosaccharides from pineapple leaves: Impact of hydrothermal pretreatment and controlled enzymatic hydrolysis

Globally, the demands for sustainably sourced functional foods like prebiotic oligosaccharides have been constantly increasing. This study assessed the potential of pineapple leaves (PL) as lignocellulosic feedstock for sustainable production of cellulose and hemicellulose-derived oligosaccharides through its hydrothermal pretreatment (HT) followed by controlled enzymatic hydrolysis. PL was subjected to HT at 160, 175, and 190 °C for 20, 30, 60, and 90 min without any catalyst for xylooligosaccharide (XOS) production, whereas, the resulting solid content after HT was subjected to controlled enzymatic hydrolysis by commercial cellulase using conduritol B epoxide (0.5-5 mM) for glucooligosaccharides (GOS) production. HT at 160 °C for 60 min resulted in maximum yield of XOS and GOS at 23.7 and 18.3 %, respectively, in the liquid phase. Controlled enzymatic hydrolysis of HT treated (160 °C) PL solids for 20 and 30 min yielded ∼ 174 mg cellobiose/g dry biomass within 24 h, indicating overall high oligosaccharide production.

Unlocking the potential of low FODMAPs sourdough technology for management of irritable bowel syndrome

Consumption of high FODMAP (Fermentable Oligo-, Di-, and Monosaccharides and Polyols) diet is the leading cause of alteration in the human gut microbiome, thereby, causing irritable bowel syndrome (IBS). Therefore, sourdough technology can be exploited for reduction of FODMAPs in various foods to alleviate the symptoms of IBS. Several microorganisms viz. Pichia fermentans, Lactobacillus fetmentum, Saccharomyces cerevisiae, Torulaspora delbrueckii, Kluyveromyces marxianus etc. have been identified for the production of low FODMAP type II sourdough fermented products. However, more research on regulation of end-product and volatilome profile is required for maximal exploitation of FODMAP-reducing microorganisms. Therefore, the present review is focused on utilisation of lactic acid bacteria and yeasts, alone and in synergy, for the production of low FODMAP sourdough foods. Moreover, the microbial bioprocessing of cereal and non-cereal based low FODMAP fermented sourdough products along with their nutritional and therapeutic benefits have been elaborated. The challenges and future prospects for the production of sourdough fermented low FODMAP foods, thereby, bringing out positive alterations in gut microbiome, have also been discussed.

Fractionation of functional oligosaccharides produced from sugarcane straw using serial nanofiltration membranes and their influence on prebiotic potential

Functional oligosaccharides are non-digestible by human gut enzymes and provide health benefits as fibers and prebiotics. The cello-oligosaccharides (COS) and xylooligosaccharides (XOS) are functional oligosaccharides obtained from xylan and cellulose, respectively, and are present in lignocellulosic material. The serial NF membranes process was performed to investigate the impact of the fractionation process on the prebiotic activity of oligosaccharides from xylan and cellulose. The NP030 (weight cut-off of 500-600 Da) and DK (weight cut-off of 150-300 Da) NF polymeric membranes were employed using defined operational conditions. The diafiltration (DF) was also investigated and it was determined that only a 1-time DF for NP030 was a more suitable strategy and improved the performance indices for short DP oligosaccharides. The short DP fractions obtained favored cell density for probiotic strains, which presented an increase on the optical density of up to 25 % after the fractionating process; enabling the use of short purified fractions in the food and pharmaceutical industry as a prebiotic ingredient.

Bioprocess development for the production of xylooligosaccharide prebiotics from agro-industrial lignocellulosic waste

The development of sustainable biorefineries and bioeconomy has been the mandate of most of the governments with major focus on restricting the climate change concerns and finding new strategies to maintain the global food supply chain. Xylooligosaccharides (XOS) are short-chain oligomers which due to their excellent prebiotic potential in the nutraceutical sector has attracted intense research focus in the recent years. The agro-industrial crop and food waste can be utilized for the production of XOS which are derived from hemicellulose fraction (xylan) of the lignocellulosic materials. The extraction of xylan, is traditionally achieved by acidic and alkaline pretreatments which, however, have limited industrial applications. The inclusion of cutting-edge and environmentally beneficial pretreatment methods and technologies such as deep eutectic solvents and green catalysts are preferred. Moreover, the extraction of xylans from biomass using combinatorial pretreatment approaches may help in economizing the whole bioprocess. The current review outlines the factors involved in the xylan extraction and depolymerization processes from different lignocellulosic biomass and the subsequent enzymatic hydrolysis for XOS production. The different types of oligosaccharides and their prebiotic potential for the growth of healthy gut bacteria have also been explained. The introduction of modern molecular technologies has also made it possible to identify enzymes and microorganisms with the desired characteristics for usage in XOS industrial production processes.

Delignified wheat straw for production of xylo-oligosaccharides and monosaccharides using acetic acid/sodium acetate solution

The production of xylo-oligosaccharides (XOS) from lignocelluloses with conjugated acid-base system is highly efficient. However, XOS production from wheat straw with conjugated system of acetic acid/sodium acetate (HAc/NaAc) has not been reported. In addition, the impact of delignification of wheat straw for XOS production was not clear. In this study, the optimal conditions for HAc/NaAc hydrolysis were: 0.4 M, molar ratio 10:1, 170 °C, and 60 min. The yield of XOS could be rose to 50.2% after the HAc/NaAc hydrolysate was hydrolyzed using xylanase. After 70.3% of lignin in wheat straw was removed by hydrogen peroxide-acetic acid treatment, the XOS yield of delignified wheat straw using HAc/NaAc reached 54.7%. Finally, a glucose yield of 96.6% was gained by cellulase from wheat straw solid. This work suggested that HAc/NaAc hydrolysis could efficiently produce XOS from wheat straw and the delignification of wheat straw was conducive to XOS and monosaccharides production.

Recent advances in bio-based extraction processes for the recovery of bound phenolics from agro-industrial by-products and their biological activity

Usually found bound to other complex molecules (e.g., lignin, hemicellulose), phenolic compounds (PC) are widely present in agro-industrial by-products, and their extraction is challenging. In recent times, research is starting to highlight the bioactive roles played by bound phenolics (BPC) in human health. This review aims at providing a critical update on recent advances in green techniques for the recovery of BPC, focusing on enzymatic-assisted (EAE) and fermentation-assisted extraction (FAE) as well as in the combination of technologies, showing variable yield and features. The present review also summarizes the most recent biological activities attributed to BPC extracts until now. The higher antioxidant activity of BPC-compared to FPC-coupled with their affordable by-product source make them medicinally potent and economically viable, promoting their integral upcycling and generating new revenue streams, business, and employment opportunities. In addition, EAE and FAE can have a biotransformative effect on the PC itself or its moiety, leading to improved extraction outcomes. Moreover, recent research on BPC extracts has reported promising anti-cancer and anti-diabetic activity. Yet further research is needed to elucidate their biological mechanisms and exploit the true potential of their applications in terms of new food products or ingredient development for human consumption.

Delignification of switchgrass for xylo-oligosaccharides production using sorbic acid hydrolysis

Organic acid as a class of hydrolysis catalysts shows great potential in the production of xylo-oligosaccharides (XOS) from lignocelluloses. However, sorbic acid (SA) hydrolysis in XOS production from lignocellulose has not been reported and it was still unclear how lignin removal affected XOS production. Herein, two factors affecting the XOS production from switchgrass by SA hydrolysis were explored: hydrolysis severity factor (Log R₀) and lignin removal. Benefiting from the lignin removal (58.4%) in switchgrass, a desired XOS yield of 50.8% with low by-products was obtained from delignified switchgrass by 3% SA hydrolysis at Log R₀ = 3.84. Under these conditions, 92.1% of glucose was obtained by cellulase hydrolysis with Tween 80 addition. From a mass balance perspective, 10.3 g of XOS and 23.7 g of glucose could be produced from 100 g switchgrass. This work proposes a novel strategy for XOS and monosaccharides production from delignified switchgrass.

Food Waste Utilization for Reducing Carbon Footprints towards Sustainable and Cleaner Environment: A Review

There is world-wide generation of food waste daily in significant amounts, leading to depletion of natural resources and deteriorating air quality. One-third of global food produced is wasted laterally with the food value chain. Carbon footprint is an efficient way of communicating the issues related to climate change and the necessity of changing behavior. Valorization or utilization of food wastes helps in resolving issues related to environment pollution. Reduction in the carbon footprint throughout the chain of food supply makes the whole process eco-friendly. Prevailing food waste disposal systems focus on their economic and environmental viability and are putting efforts into using food waste as a resource input to agriculture. Effective and advanced waste management systems are adopted to deal with massive waste production so as to fill the gap between the production and management of waste disposal. Food waste biorefineries are a sustainable, eco-friendly, and cost-effective approach for the production of platform chemicals, biofuels, and other bio-based materials. These materials not only provide sustainable resources for producing various chemicals and materials but have the potential to reduce this huge environmental burden significantly. In this regard, technological advancement has occurred in past few years that has proven suitable for tackling this problem.

Sustainable Food Systems: The Case of Functional Compounds towards the Development of Clean Label Food Products

The addition of natural components with functional properties in novel food formulations confers one of the main challenges that the modern food industry is called to face. New EU directives and the global turn to circular economy models are also pressing the agro-industrial sector to adopt cradle-to-cradle approaches for their by-products and waste streams. This review aims to present the concept of “sustainable functional compounds”, emphasizing on some main bioactive compounds that could be recovered or biotechnologically produced from renewable resources. Herein, and in view of their efficient and “greener” production and extraction, emerging technologies, together with their possible advantages or drawbacks, are presented and discussed. Μodern examples of novel, clean label food products that are composed of sustainable functional compounds are summarized. Finally, some action plans towards the establishment of sustainable food systems are suggested.

De Novo Metagenomic Analysis of Microbial Community Contributing in Lignocellulose Degradation in Humus Samples Harvested from Cuc Phuong Tropical Forest in Vietnam

We aimed to investigate the microbial diversity, mine lignocellulose-degrading enzymes/proteins, and analyze the domain structures of the mined enzymes/proteins in humus samples collected from the Cuc Phuong National Park, Vietnam. Using a high-throughput Illumina sequencer, 52 Gbs of microbial DNA were assembled in 2,611,883 contigs, from which 4,104,872 open reading frames (ORFs) were identified. Among the total microbiome analyzed, bacteria occupied 99.69%; the five ubiquitous bacterial phyla included Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes, and Acidobacteria, which accounted for 92.59%. Proteobacteria (75.68%), the most dominant, was 5.77 folds higher than the second abundant phylum Bacteroidetes (13.11%). Considering the enzymes/proteins involved in lignocellulose degradation, 22,226 ORFs were obtained from the annotation analysis using a KEGG database. The estimated ratio of Proteobacteria/Bacteroidetes was approximately 1:1 for pretreatment and hemicellulases groups and 2.4:1 for cellulases. Furthermore, analysis of domain structures revealed their diversity in lignocellulose-degrading enzymes. CE and PL were two main families in pretreatment; GH1 and GH3-FN3 were the highest domains in the cellulase group, whereas GH2 and GH43 represented the hemicellulase group. These results validate that natural tropical forest soil could be considered as an important source to explore bacteria and novel enzymes/proteins for the degradation of lignocellulose.

Extraction of Pectin from Orange Peel and Study of Its Protective Effect Against Loperamide-Induced Impaired Gastrointestinal Motor Functions and Oxidative Stress in Rats

Pectin is a polysaccharide attached to carbohydrates. These are substances exclusively of plant origin. The aim of the present study is to evaluate the laxative effects of orange peel pectin extract (OPPE) against constipation induced by loperamide (LOP) in rats. Rats were equally divided into six groups and treated daily 1 week as follows: Control, LOP (3 mg/kg, body weight [b.w.], Per Os [p.o.]), LOP+yohimbine (2 mg/kg, b.w., i.p.), and LOP+OPPE (6.25, 12.5, and 25 mg/kg, b.w., p.o.). At the end of the experiment, the effects of OPPE were assessed by fecal parameters (numbers, weight, and water content), gastrointestinal transit, gastric emptying, serum metabolic parameter changes, intestinal and colon mucosa oxidative stress, and the histological examination. The defecation test showed that administration of LOP (3 mg/kg, b.w., p.o.) leads to the production of remarkable constipation. Indeed, the number and water content of stools decreased (25.50 [n/24 h] and 29.86%) significantly (P < .05). Acute pretreatment with OPPE significantly and dose dependently accelerated the stool moistening and allowed an increase of stool weight (2.85, 3.61, 3.93 [g/24 h/rat]) as well as the frequency of defecation (47.36, 54.54, and 56.26 [n/24 h]). OPPE also significantly (P < .05) and dose dependently increased the intestinal motility (70.78%, 73.33%, and 75.01%) and gastric emptying. LOP-induced reduction (P < .05) of intestinal secretion was accompanied by a colonic and small bowel oxidative stress status and histological changes, which was attenuated by OPPE treatment. The findings of this study indicate that OPPE possesses an important role in the gastrointestinal motility regulation, and thus lend pharmacological credence to the suggested use of the natural pectin for the treatment, management, and/or control of constipation.

Recent advancements in prebiotic oligomers synthesis via enzymatic hydrolysis of lignocellulosic biomass

Interest in functional food, such as non-digestible prebiotic oligosaccharides is increasing day by day and their production is shifting toward sustainable manufacturing. Due to the presence of high carbohydrate content, lignocellulosic biomass (LCB) is the most-potential, cost-effective and sustainable substrate for production of many useful products, including lignocellulose-derived prebiotic oligosaccharides (LDOs). These have the same worthwhile properties as other common oligosaccharides, such as short chain carbohydrates digestible to the gut flora but not to humans mainly due to their resistance to the low pH and high temperature and their demand is constantly increasing mainly due to increased awareness about their potential health benefits. Despite several advantages over the thermo-chemical route of synthesis, comprehensive and updated information on the conversion of lignocellulosic biomass to prebiotic oligomers via controlled enzymatic saccharification is not available in the literature. Thus, the main objective of this review is to highlight recent advancements in enzymatic synthesis of LDOs, current challenges, and future prospects of sustainably producing prebiotic oligomers via enzymatic hydrolysis of LCB substrates. Enzyme reaction engineering practices, custom-made enzyme preparations, controlled enzymatic hydrolysis, and protein engineering approaches have been discussed with regard to their applications in sustainable synthesis of lignocellulose-derived oligosaccharide prebiotics. An overview of scale-up aspects and market potential of LDOs has also been provided.

The direct and indirect effects of bioactive compounds against coronavirus

Emerging viruses are known to pose a threat to humans in the world. COVID‐19, a newly emerging viral respiratory disease, can spread quickly from people to people via respiratory droplets, cough, sneeze, or exhale. Up to now, there are no specific therapies found for the treatment of COVID‐19. In this sense, the rising demand for effective antiviral drugs is stressed. The main goal of the present study is to cover the current literature about bioactive compounds (e.g., polyphenols, glucosinolates, carotenoids, minerals, vitamins, oligosaccharides, bioactive peptides, essential oils, and probiotics) with potential efficiency against COVID‐19, showing antiviral activities via the inhibition of coronavirus entry into the host cell, coronavirus enzymes, as well as the virus replication in human cells. In turn, these compounds can boost the immune system, helping fight against COVID‐19. Overall, it can be concluded that bioactives and the functional foods containing these compounds can be natural alternatives for boosting the immune system and defeating coronavirus.

New perspectives for banana peel polysaccharides and their conversion to oligosaccharides

Banana peel is a source of polysaccharides: pectin, hemicellulose and cellulose. Recent studies have shown that these carbohydrate fractions can be converted into oligomers, which have applications in food, feed and pharmaceuticals, claiming important technical, functional and biological activities. Potential prebiotic activity of pectin and cellulose oligosaccharides obtained from banana peel was already reported. Based on technologies developed for fractionation and extraction of polysaccharides, such as pectin, hemicellulose and cellulose, banana peel can be explored to obtain functional oligosaccharides.

Xylooligosaccharides induce stomatal closure via salicylic acid signaling-regulated reactive oxygen species and nitric oxide production in Arabidopsis

Xylooligosaccharides (XOS) are the major coproducts of biofuel production and the most representative functional sugar enhancing animal physiology. However, little is known regarding the biological relevance of XOS to plants. Here, we found XOS triggered stomatal closure in Arabidopsis in a dose-dependent manner. Pamarcological data showed that XOS-induced stomatal closure was markedly inhibited by catalase (CAT, a reactive oxygen species [ROS] scavenger), salicylhydroxamic acid (SHAM, a peroxidase inhibitor), and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO, a nitric oxide [NO] scavenger). Moreover, XOS induced the production of ROS and NO in guard cells of Arabidopsis. ROS production was strongly restricted by CAT and SHAM, but was unaffected by treatment with diphenyleneiodonium chloride (DPI, an NADPH oxidase inhibitor) or cPTIO. NO production was suppressed by CAT, SHAM, and cPTIO, but not by DPI. The elevation of ROS level mediated by SHAM-sensitive peroxidases occurred upstream of NO. Additionally, XOS-triggered stomatal closure and ROS and NO accumulation were significantly impaired in npr1 (salicylic acid signaling) mutant plants, but were not in jar1 (jasmonic acid signaling) or ein2 (ethylene signaling) mutant plants. Furthermore, XOS-induced stomatal closure was unaffected in both ost1 and atrbohD atrbohF (abscisic acid [ABA] signaling) mutant plants. Therefore, these results indicated that the biotic sugar, XOS, can elicit stomatal closure via salicylic acid signaling-mediated production of ROS and NO, in a manner independent of ABA signaling.

Evaluation of spent mushroom substrate after cultivation of Pleurotus ostreatus as a new raw material for xylooligosaccharides production using crude xylanases from Aspergillus flavus KUB2

Xylooligosaccharides (XOS), a novel functional food and feed ingredient, can be produced from lignocellulosic biomass. In this study, spent mushroom substrate (SMS) gathered after Pleurotus ostreatus cultivation was investigated for its potential as a new raw material for XOS production using crude xylanases produced in-house from Aspergillus flavus KUB2. Xylan was extracted from SMS using the alkaline extraction method. The highest true recovery of xylan (20.76%) and the relative recovery of xylan (83.73%) were obtained from SMS extracted with 4 M NaOH. Enzymatic hydrolysis of SMS-extracted xylan using crude fungal xylanases from A. flavus KUB2 produced a maximum total XOS in the range 1.37-1.48 mg/ml, which was mainly composed of XOS with a low degree of polymerization (xylobiose and xylotriose). XOS derived from SMS-extracted xylan positively influenced the growth of probiotic bacteria, suggesting the prebiotic nature of XOS. The results indicated that XOS with prebiotic properties can be produced from SMS xylan using crude xylanases without any purification, which offers economic potential for food and feed applications.

Cello-oligosaccharides production from lignocellulosic biomass and their emerging prebiotic applications

Cello-oligosaccharides (COS) are linear oligosaccharides composed of β-1,4-linked glucopyranose units. They comprise a group of important new oligosaccharides of significant interest and potential applications in the pharmaceutical, food, chemical, and feed industries, currently emerging as potential prebiotic compounds. COS from lignocellulosic biomass, specifically the agro-industrial residues and by-products of the forestry industry, constitute a new attractive process that imposes the sustainable use of biomass resources. Two main strategies have been used for the production of COS: acid-based and enzyme-based cellulose hydrolysis. The latter has been considered more attractive due to the use of milder reaction conditions and less production of monomers. This review summarizes that although COS is emerging as a potential prebiotic with also other potential applications, there is a lack of information regarding the large-scale production, which could be associated with the recalcitrant nature of cellulose compared to other polysaccharides, which hinders the hydrolysis of its dense network.

Dietary fibers as beneficial microbiota modulators: A proposed classification by prebiotic categories

Dietary fiber is a group of heterogeneous substances that are neither digested nor absorbed in the small intestine. Some fibers can be classified as prebiotics if they are metabolized by beneficial bacteria present in the hindgut microbiota. The aim of this review was to specify the prebiotic properties of different subgroups of dietary fibers (resistant oligosaccharides, non-starch polysaccharides, resistant starches, and associated substances) to classify them by prebiotic categories. Currently, only resistant oligosaccharides (fructans [fructooligosaccharides, oligofructose, and inulin] and galactans) are well documented as prebiotics in the literature. Other fibers are considered candidates to prebiotics or have prebiotic potential, and apparently some have no prebiotic effect on humans. This dietary fiber classification by the prebiotic categories contributes to a better understanding of these concepts in the literature, to the stimulation of the processing and consumption of foods rich in fiber and other products with prebiotic properties, and to the development of protocols and guidelines on food sources of prebiotics.

Deciphering effectual binding potential of xylo-substrates towards xylose isomerase and xylokinase through molecular docking and molecular dynamic simulation

Xylooligosaccharides (XOS) such as xylobiose and xylotriose are prebiotics with important functions and relevance and the study of interaction mechanism between these substrate and their respective enzymes has scope and applications. Thus, the present study aimed to decipher the interaction mechanisms of xylose isomerase (XylA) and xylokinase (XylB) towards their xylo-substrates namely xylobiose and xylotriose by computational modeling and molecular dynamic simulation studies. The three-dimensional structures of XylA and XylB, not available in their native forms, were predicted, energy minimized and validated by various computational biology tools and software. The binding mechanisms of xylobiose and xylotriose towards XylA and XylB were modeled by molecular docking and the stability of the docked complexes was confirmed by molecular dynamic (MD) simulation. The current study suggested that the theoretical models of XylA and XylB possessed good stereo-chemical validity, structural stabilities and minimum energy conformers. The molecular docking studied showed that xylotriose showed better binding interactions to XylA than xylobiose and xylobiose showed better binding interaction to XylB than xylotriose with ideal root mean square deviation (RMS), minimum binding energy (kcal/mol), hydrogen bonding and weak interactions. The MD simulation confirmed the stabilities of the docked complexes predicted by docking studies. The study suggested that interactions between the probiotics and prebiotics and provides the novel insights in exploring synbiotics as functional foods towards their futuristic applications. [Formula: see text]HighlightsThis study deciphers the interactions of xylosubstrates to XylA and XylB.The XylA and XylB possessed ideal structural stability and stereochemistryXylotriose and Xylobiose showed significant interactionsThe interactions of Xylotriose-XylA and Xylobiose-XylB were found stable in MD studies.Communicated by Ramaswamy H. Sarma.

Evaluating Feruloyl Esterase—Xylanase Synergism for Hydroxycinnamic Acid and Xylo-Oligosaccharide Production from Untreated, Hydrothermally Pre-Treated and Dilute-Acid Pre-Treated Corn Cobs

Agricultural residues are considered the most promising option as a renewable feedstock for biofuel and high valued-added chemical production due to their availability and low cost. The efficient enzymatic hydrolysis of agricultural residues into value-added products such as sugars and hydroxycinnamic acids is a challenge because of the recalcitrant properties of the native biomass. Development of synergistic enzyme cocktails is required to overcome biomass residue recalcitrance, and achieve high yields of potential value-added products. In this study, the synergistic action of two termite metagenome-derived feruloyl esterases (FAE5 and FAE6), and an endo-xylanase (Xyn11) from Thermomyces lanuginosus, was optimized using 0.5% (w/v) insoluble wheat arabinoxylan (a model substrate) and then applied to 1% (w/v) corn cobs for the efficient production of xylo-oligosaccharides (XOS) and hydroxycinnamic acids. The enzyme combination of 66% Xyn11 and 33% FAE5 or FAE6 (protein loading) produced the highest amounts of XOS, ferulic acid, and p-coumaric acid from untreated, hydrothermal, and acid pre-treated corn cobs. The combination of 66% Xyn11 and 33% FAE6 displayed an improvement in reducing sugars of approximately 1.9-fold and 3.4-fold for hydrothermal and acid pre-treated corn cobs (compared to Xyn11 alone), respectively. The hydrolysis product profiles revealed that xylobiose was the dominant XOS produced from untreated and pre-treated corn cobs. These results demonstrated that the efficient production of hydroxycinnamic acids and XOS from agricultural residues for industrial applications can be achieved through the synergistic action of FAE5 or FAE6 and Xyn11.

Production of Oligosaccharides from Agrofood Wastes

The development of biorefinery processes to platform chemicals for most lignocellulosic substrates, results in side processes to intermediates such as oligosaccharides. Agrofood wastes are most amenable to produce such intermediates, in particular, cellooligo-saccharides (COS), pectooligosaccharides (POS), xylooligosaccharides (XOS) and other less abundant oligomers containing mannose, arabinose, galactose and several sugar acids. These compounds show a remarkable bioactivity as prebiotics, elicitors in plants, food complements, healthy coadyuvants in certain therapies and more. They are medium to high added-value compounds with an increasing impact in the pharmaceutical, nutraceutical, cosmetic and food industries. This review is focused on the main production processes: autohydrolysis, acid and basic catalysis and enzymatic saccharification. Autohydrolysis of food residues at 160–190 °C leads to oligomer yields in the 0.06–0.3 g/g dry solid range, while acid hydrolysis of pectin (80–120 °C) or cellulose (45–180 °C) yields up to 0.7 g/g dry polymer. Enzymatic hydrolysis at 40–50 °C of pure polysaccharides results in 0.06–0.35 g/g dry solid (DS), with values in the range 0.08–0.2 g/g DS for original food residues.

Purification and characterization of an endo-xylanase from Trichoderma sp., with xylobiose as the main product from xylan hydrolysis

Fungal endo-β-1,4-xylanases (endo-xylanases) can hydrolyze xylan into xylooligosaccharides (XOS), and have potential biotechnological applications for the exploitation of natural renewable polysaccharides. In the current study, we aimed to screen and characterize an efficient fungal endo-xylanase from 100 natural humus-rich soil samples collected in Guizhou Province, China, using extracted sugarcane bagasse xylan (SBX) as the sole carbon source. Initially, 182 fungal isolates producing xylanases were selected, among which Trichoderma sp. strain TP3-36 was identified as showing the highest xylanase activity of 295 U/mL with xylobiose (X2) as the main product when beechwood xylan was used as substrate. Subsequently, a glycoside hydrolase family 11 endo-xylanase, TXyn11A, was purified from strain TP3-36, and its optimal pH and temperature for activity against beechwood xylan were identified to be 5.0 and 55 °C, respectively. TXyn11A was stable across a broad pH range (3.0-10.0), and exhibited strict substrate specificity, including xylan from beechwood, wheat, rye, and sugarcane bagasse, with K_m and V_max values of 5 mg/mL and 1250 μmol/mg min, respectively, toward beechwood xylan. Intriguingly, the main product obtained from hydrolysis of beechwood xylan by TXyn11A was xylobiose, whereas SBX hydrolysis resulted in both X2 and xylotriose. Overall, these characteristics of the endo-xylanase TXyn11A indicate several potential industrial applications.