Xylose Ratio Research Articles

Structural characterization of noni (Morinda citrifolia L.) pectin and its inhibitory activity on pancreatic lipase

This study aimed to investigate the physicochemical properties and biological activities of noni pectin (NP) extracted using various solvents, three fractions of noni pectin were obtained using traditional chemical and deep eutectic solvents. NPs are composed of various ratios of galacturonic acid, arabinose, rhamnose, xylose, glucose, and galactose with different yields, molecular weights, esterification degrees (DE), and microstructures. Among the fractions, noni pectin extracted with Betaine-citric acid (BNP) exhibited higher molecular weight, degree for esterification and pancreatic lipase (PL) inhibitory activity than the other fractions. Enzyme kinetic analysis indicated that BNP inhibited PL via a noncompetitive mechanism. BNP significantly altered the secondary structure of PL and quenched PL fluorescence, suggesting a static quenching mechanism. Isothermal titration calorimetry (ITC) further demonstrated that the binding of BNP to PL was spontaneous and driven by enthalpy, primarily mediated by hydrogen bonding and van der Waals forces. Molecular docking simulations also confirmed strong noncovalent interactions (hydrogen bonding and van der Waals forces) between BNP and PL. This study validated the high efficiency of the deep eutectic solvent-extracted noni pectin fraction in pancreatic lipase inhibition.

The role of arabinoxylan purified from wheat bran in bread and biscuits: Impacts on digestibility and colonic fermentability in vitro

In this study, arabinoxylan (AX) isolated from wheat bran was used to prepare AX-fortified bread and biscuits, and the effects of the amount and method of AX addition on the nutritional properties of baked products were investigated through simulated digestibility and colonic simulated fermentability analysis in vitro. The purified AX demonstrated a high total sugar content (92.75%), high molecular weight (Mw) (669.8 kDa), low polymer dispersity index (PDI) and low arabinose to xylose (A/X) ratio (1.21). In vitro digestibility test indicated that AX addition could dose-dependently inhibit the starch digestibility in both bread and biscuits. Most importantly, it could also dose-dependently transfer more starch and protein into the colon through the gastrointestinal tract, leading to the changes in total amount and chemical composition of food residues. Results from the in vitro fermentability test showed that alterations in the composition of food residue affected its fermentability: a high relative ratio of carbohydrate to protein could enhance its prebiotic effect. This study provides valuable insights into the role of dietary fibres in baked foods, aiming to achieve precise nutrition for high-fibre food products.

Mathematical modeling of fermentation from glucose, xylose, and food waste of clostridia sp. strain BOH3 for the production of ABE solvents and hydrogen

In this study we develop a robust, structured dynamic model of ABE and hydrogen production using Clostridium BOH3 strain. The model represents simultaneous fermentation of glucose and xylose, and concurrent saccharification and fermentation when grown on a variety of complex feedstocks, using only a single adjustable parameter. The model simulations were developed and validated with experimental data of BOH3 fermentations from the literature. Sugar consumption and ABE production dynamics are successfully predicted at different glucose to xylose ratios, and from hydrolyzed lignocellulose, representative of horticultural waste. Butanol and hydrogen production are in close agreement with the experimental data in simulations with rice starch and food waste as substrates. The sensitivity analysis highlights the important roles of xylose transport and xylose kinase on the xylose consumption and butanol formation, in accordance with experimental findings on how these enzymes enable the efficient xylose utilization by BOH3.

Nanostructures of etherified arabinoxylans and the effect of arabinose content on material properties

To further our understanding of a thermoplastic arabinoxylan (AX) material obtained through an oxidation-reduction-etherification pathway, the role of the initial arabinose:xylose ratio on the material properties was investigated. Compression molded films with one molar substitution of butyl glycidyl ether (BGE) showed markedly different tensile behaviors. Films made from low arabinose AX were less ductile, while those made from high arabinose AX exhibited elastomer-like behaviors. X-ray scattering confirmed the presence of nanostructure formation resulting in nano-domains rich in either AX or BGE, from side chain grafting. The scattering data showed variations in the presence of ordered structures, nano-domain sizes and their temperature response between AX with different arabinose contents. In dynamic mechanical testing, three transitions were observed at approximately −90 °C, −50 °C and 80 °C, with a correlation between samples with more structured nano-domains and those with higher onset transition temperatures and lower storage modulus decrease. The mechanical properties of the final thermoplastic AX material can therefore be tuned by controlling the composition of the starting material.

Molecular characterization, rheological properties, and prebiotic properties of arabinoxylans from waxy and sweet corn cobs

AbstractBackground and ObjectivesArabinoxylan (AX) has diverse physicochemical properties and biological activities, related to the structural differences caused by various sources and extraction methods. We study the differences in molecular characterization, rheological properties, and prebiotic properties in waxy and sweet corn cobs AX, and water‐extractable and water‐unextractable arabinoxylan (EAX, UAX).FindingsThe arabinose to xylose ratios (Ara/Xyl) of waxy corn cobs AX were lower than that of sweet corn cobs AX. Also, the viscosity of all samples increased with increasing concentration and decreasing temperature. In the vitro probiotic fermentation, waxy corn cobs AX was stronger in promoting the growth of probiotics than AX from sweet corn cobs. Probiotics in the AX group were predominantly acetic acid and butyric acid producers, and the waxy corn cobs AX group produced more short‐chain fatty acids than the sweet corn cobs AX group, resulting in a lower pH in the waxy corn cobs AX group.ConclusionsEAX and UAX also showed significant variations in molecular characterization, viscosity, and prebiotic properties. Waxy corn cobs AX had stronger prebiotic activity than sweet corn cobs AX.Significance and NoveltyThis experiment provides a theoretical and experimental basis for studying the prebiotic properties of AX, which could guide the application of fresh corn cobs‐derived AX.

Using in feed xylanase or stimbiotic to reduce the variability in corn nutritive value for broiler chickens

This study investigated the effects of xylanase and stimbiotic (fiber fermentation enhancer) on the response of broiler chickens fed different corn varieties and determine correlations between variables of interest. Four corn genetic varieties were selected based on their range in nutrient composition. Diets containing 600 g/kg of each corn were supplemented with 0 or 100 g/ton of xylanase or stimbiotic. A total of 1,152 one-day-old male broiler chicks (Ross 308) were divided into 12 treatments, each with 8 pens and 12 birds per pen, for a 21-day study. On d 21, performance parameters were measured, and the ileal energy and organic matter (OM) digestibility and cecal xylanase activity determined. Stimbiotic supplementation improved mFCR compared with all other treatments. There was a treatment by corn variety interaction for body weight (BW), BW gain and coefficient of variation (CV) of BW (P ≤ 0.05). Birds fed corn Variety 1 (highest neutral dietary fiber, protein and soluble arabinoxylan content) supplemented with stimbiotic had the highest BW, while Variety 2 control diet had the lowest. The BW CV in corn Variety 2 was the highest, which improved with stimbiotic supplementation. The BW CV in corn Variety 1 responded better to stimbiotic than xylanase. There were no treatment differences on BW CV in corn Varieties 3 and 4. The lowest OM digestibility was observed in birds fed corn Variety 1 with xylanase, and the highest value was associated with corn Variety 3 with xylanase (highest total arabinoxylan). Xylanase and stimbiotic supplementation increased the endogenous xylanase activity regardless of the corn variety (P ≤ 0.05). Positive correlations between corn fiber contents and phytic acid and the arabinose:xylose ratio were seen, while nonstarch polysaccharide content was negatively correlated with apparent metabolizable energy. In conclusion, corn variety influenced nutrient digestibility and broiler chicken growth. The response to supplementation with xylanase or stimbiotic varied based on the nutritional profile of corn with regards to improvements in digestibility and performance in broiler chickens.

Mycoprotein Production by Submerged Fermentation of the Edible Mushroom Pleurotus ostreatus in a Batch Stirred Tank Bioreactor Using Agro-Industrial Hydrolysate.

The demand for cheap, healthy, and sustainable alternative protein sources has turned research interest into microbial proteins. Mycoproteins prevail due to their quite balanced amino acid profile, low carbon footprint and high sustainability potential. The goal of this research was to investigate the capability of Pleurotus ostreatus to metabolize the main sugars of agro-industrial side streams, such as aspen wood chips hydrolysate, to produce high-value protein with low cost. Our results indicate that P. ostreatus LGAM 1123 could be cultivated both in a C-6 (glucose)- and C-5(xylose)-sugar-containing medium for mycoprotein production. A mixture of glucose and xylose was found to be ideal for biomass production with high protein content and rich amino acid profile. P. ostreatus LGAM 1123 cultivation in a 4 L stirred-tank bioreactor using aspen hydrolysate was achieved with 25.0 ± 3.4 g L-1 biomass production, 1.8 ± 0.4 d-1 specific growth rate and a protein yield of 54.5 ± 0.5% (g/100 g sugars). PCA analysis of the amino acids revealed a strong correlation between the amino acid composition of the protein produced and the ratios of glucose and xylose in the culture medium. The production of high-nutrient mycoprotein by submerged fermentation of the edible fungus P. ostreatus using agro-industrial hydrolysates is a promising bioprocess in the food and feed industry.

Optimization of co-culture condition with respect to aeration and glucose to xylose ratio for bioethanol production

ABSTRACT The present study was designed to find a suitable microaerobic condition and ratio of glucose and xylose for maximum ethanol production using co-culture of Saccharomyces cerevisiae and Pichia stipitis. The maximum ethanol concentration and yield were achieved at 0.05 vvm aeration rate and 2:1 glucose/xylose ratio. The co-culture resulted in maximum ethanol concentration, ethanol yield, and volumetric productivity of 12.33 ± 0.10 g/L, 0.43 g/g, and 0.26 g/L/h, respectively. While, the monoculture of P. stipitis resulted in 8.96 ± 0.13 g/L, 0.36 g/g, and 0.19 g/L/h respectively. The fermentation carried out in microaerobic mode delivered 10.68% and 10.56% more ethanol concentration and ethanol yield respectively from glucose compared to the combination of anaerobic and microaerobic mode. Also, the glucose uptake rate increased to 0.83 g/L/h, which corresponds to an improvement of 50.16%, suggesting that the lower microaerophilic condition not only supports P. stipitis metabolism but also does S. cerevisiae to convert glucose faster in a co-culture system. Hence, co-culture cultivation in microaerobic mode would be a better condition to achieve maximum ethanol and productivity.

Carbon/nitrogen ratio as a tool to enhance the lipid production in Rhodosporidium toruloides-1588 using C5 and C6 wood hydrolysates

The interest in microbial lipids has recently increased because of their wide use to produce several value-added compounds in the biofuel, pharmaceutical and food industries. Oleaginous yeast such as Rhodosporidium toruloides could be an efficient option because of its ability to consume five-carbon sugars, high lipid accumulation, and tolerance to toxic compounds such as furans, phenolic compounds, and organic acids. The present study aims to investigate the effect of different initial sugar ratios, in combination with different carbon/nitrogen ratios, and the use of dibasic sodium phosphate (Na2HPO4) as an inducer on cell biomass production, sugar consumption, and lipid accumulation by Rhodosporidium toruloides-1588. The investigation showed a maximum lipid accumulation of 5.35 gL-1 (0.28 g of lipids/g of sugar) under the culture conditions of initial glucose: xylose ratio of 1:1, C/N ratio of 70, and Na2HPO4 concentration of 1.05 gL-1. The predominant lipids composition was palmitic, stearic, oleic, and linoleic acids which could be used as a suitable feedstock for biofuel production. Additionally, under the optimal conditions (initial glucose: xylose ratio of 1:1, 1.19 gL-1 of Na2HPO4 and C/N ratio of 70.50) an increase of 10.5% and 7.5% in lipid accumulation was observed, compared with control treatments (glucose and xylose, respectively). In addition, the study shows the ability of R. toruloides-1588 to tolerate inhibitors, a feature that could be a promising alternative to increase the feasibility of the microbial lipid production process using undetoxified wood hydrolysate as a sustainable culture media.

Structural and nutritional properties of psyllium husk arabinoxylans with special reference to their antioxidant potential

ABSTRACT The current research aimed to extract and characterize arabinoxylans (AX) from psyllium seeds husk for their nutritional and structural properties. For this purpose, psyllium husk (PH) was procured from the local market and subjected for the nutritional profile, dietary fiber (DF) composition, and AXs extraction. The extraction of AXs from psyllium seed husk was done through enzymatic method and Fourier transform infrared (FTIR) spectroscopy was used for its structural characterization. Further, the antioxidant activity of AXs was also elucidated using ferric reducing antioxidant power (FRAP) and diphenyl picryl hydrazyl (DPPH) assays. Results showed that psyllium seed husk is a good source of DFs (61.5 ± 2.6%) and the proximate composition including moisture, ash, crude fat, crude protein, crude fibers, and Nitrogen free extract (NFE) was 4.9 ± 0.01, 4.1 ± 0.01, 1.2 ± 0.01, 3.9 ± 0.05, 20.23 ± 0.4 and 78.2 ± 4.01 g/100 g, respectively. Furthermore, AXs content was 68.29 ± 3.4 g/100 g of PH. Different monosaccharides including xylose, arabinose, rhamnose, glucose, and galactose contents in PHAXs were 64.23 ± 1.04%, 13.38 ± 0.16%, 1.43 ± 0.04%, 1.89 ± 0.05%, and 3.64 ± 0.07%, respectively. FTIR absorption peaks from 900 to 1100 cm−1 showed spectra of AXs with the highest peak from 980 to 1015 cm−1 reflecting arabinose and xylose ratio. Additionally, the substitution positions on the xylan backbone were 2800–3400 cm−1 of O-H stretching vibrations and peaks of C-H stretching at 2853 and 2923 cm−1. The antioxidant activity of PHAXs exhibited that the FRAP value of extracted AXs was 1.39 ± 0.06 μmol Fe2+/g and the DPPH value was 3.01 ± 0.15 Trolox mg/g. It is depicted that PH is a good source of AXs (non-starch polysaccharide) with better antioxidant potential.

Effect of extrusion and semi-solid enzymatic hydrolysis modifications on the quality of wheat bran and steamed bread containing bran

In this study, raw wheat bran was modified by extrusion combined with semi-solid enzymatic hydrolysis. After modification, the percentage of soluble dietary fiber in wheat bran increased from 3.3% to 8.1%. The amount of soluble fiber as a percentage of total fiber increased from 6.2% to 16.4%. Modified wheat bran showed higher molar ratios of arabinose and xylose, larger polysaccharide molecular weight, and looser microstructure, compared with raw wheat bran. The dough with modified wheat bran showed similar formation time and water absorption as the wheat flour and better air-holding capacity than wheat flour. The steamed bread containing modified wheat bran showed better sensory qualities, and lower starch digestibility in vitro than the steamed bread containing raw wheat bran. In summary, the results suggest that the wheat bran modified by extrusion combined with semi-solid enzymatic hydrolysis has good potential as a functional ingredient in staple foods.

Structural characteristic of pectin-glucuronoxylan complex from Dolichos lablab L. hull

Polysaccharides are important constituents in Dolichos lablab hull. Herein, pectin-glucuronoxylan complex from D. lablab hull designated as DLHP-3 (D. lablab hull polysaccharide,) was prepared by ion exchange and gel permeation chromatography, and further characterized by acid degradation and enzymatic hydrolysis, methylation combined with GC–MS, NMR and MALDI-TOF-MS analysis. Both of pectin and glucuronoxylan regions were found in DLHP-3. The glucuronoxylan region consisted of a →4)-β-Xylp-(1→ backbone with branches of α-GlcpA-(1→ substituted at O-2 site, and the ratio of xylose to glucuronic acid was about 5:1. Acetyl groups were mainly attached to O-3 site of →2,4)-β-Xylp-(1→ residues. The main chain of pectin region could be represented by →4)-α-GalpA-(1→4)-α-GalpA-(1→ and →2)-α-Rhap-(1→4)-α-GalpA-(1→ with partial methyl-esterification. The side chains were deduced to embrace arabinan and arabinogalactan linked to rhamnogalacturonan-I region. Pectin was probably covalently bound to glucuronoxylan. Our findings uncovered the molecular structure of pectin-glucuronoxylan complex from D. lablab hull.

Influence of carbon and nitrogen sources on structural features and immunomodulatory activity of exopolysaccharides from Ganoderma lucidum

In this work, the effects of various carbon and nitrogen sources on structural features and immunomodulatory activity of exopolysaccharides (EPS) from Ganoderma lucidum were studied. When glucose and yeast powder were used as carbon and nitrogen sources, the apparent viscosity of fermentation broth and EPS yield and the corresponding sugar content were higher than those cultured with other carbon and nitrogen sources. The main polysaccharide components (20E) with molecular weights ranging from 2.78 × 106 to 3.96 × 106 g/mol were isolated from fermentation broth through 20% ethanol precipitation. Monosaccharide analysis showed that the carbon source significantly affected the monosaccharide compositions of 20E, and the initial carbon source of the medium accounted for the largest proportion of monosaccharide in 20E. The immunoenhancing activities on inducing NF-κB activation by 20E fractions from different carbon and nitrogen combinations exhibited significant differences. Correlation analysis demonstrated that the immunomodulatory activity of 20E fractions was positively correlated with sugar contents and the molar ratios of glucose, while it was negatively correlated with the molar ratios of xylose. As the structural features and biological activities of EPS are highly dependent on the polysaccharide medium composition, this variability can be used advantageously to produce tailor-made polysaccharides with specific applications.

Electroreforming of Glucose/Xylose Mixtures On PdAu Based Nanocatalysts

AbstractThe electroreforming of glucose/xylose mixtures has been evaluated at Pd1‐xAux/C anodes in 0.10 mol L−1 NaOH electrolyte. The catalysts synthesized by a wet chemistry route are comprehensively characterized by physicochemical and electrochemical techniques. From linear scan voltammetry and in situ Fourier transform infrared spectroscopy measurements, it was shown that the Pd0.3Au0.7/C material led to the best electrocatalytic behavior towards the electrooxidation of glucose/xylose mixtures in terms of activity (higher current densities at lower potentials) and selectivity (lower dissociative adsorption). Six‐hour chronoamperometry measurements were performed at 293 K in a 25 cm2 electrolysis cell at +0.4 V and +0.6 V and the reaction products were analyzed by high performance liquid chromatography. The main products were gluconate and xylonate, but the contributions of xylose to all formed products was always lower in percentages than the initial xylose ratios in solutions, showing that glucose was more electro‐reactive than xylose at Pd0.3Au0.7 surface.

Functional characterization of a GH62 family α-L-arabinofuranosidase from Eupenicillium parvum suitable for monosaccharification of corncob arabinoxylan in combination with key enzymes

Corncob rich in arabinoxylan is an important raw material widely used in bio-refinery. Complete saccharification of arabinoxylan depends on the synergism of different enzymes including α-L-arabinofuranosidase (ABF). This study aimed to investigate the functional characteristics of a new ABF EpABF62A belonging to glycoside hydrolase (GH) 62 family from the fungus Eupenicillium parvum, and to explore its potential in the saccharification of corncob arabinoxylan. The recombinant EpABF62A showed high activity against wheat arabinoxylan and rye arabinoxylan, with the optimal temperature of 55 °C and pH of 4.5. The protein contains an N-terminal cellulose-binding domain family 1 (CBM_1) domain, and displayed a 59.5% absorption rate to phosphoric acid swollen cellulose. Regioselectivity analysis indicated that the enzyme selectively removed α-1,2 or α-1,3 linked arabinofuranosyl residues on mono-substituted xylose residues on arabinoxylan. Corncob arabinoxylans (CAX1 or CAX2) with different (low or high) branching degrees were extracted from the raw material by alkaline hydrogen peroxide pretreatment and graded ethanol precipitation. Single EpABF62A removed 69.5% or 67.1% arabinose from CAX1 or CAX2, respectively. EpABF62A combined with a GH10 xylanase, a GH43 β-D-xylosidase and a GH67 α-glucuronidase released 75.0% or 64.5% xylose from CAX1 or CAX2, respectively. The addition of the four hemicellulases enhanced the saccharification the solid fraction of the pretreated corncob by the commercial cellulase Cellic® CTec2, and the conversion ratios of glucose, xylose and arabinose were up to 94.0%, 91.8% and 82.6%, respectively.

Isolation, structural modification, characterization, and bioactivity of polysaccharides from Folium Isatidis

The purification process of Folium Isatidis polysaccharide (FIP) was optimized by response surface method (RSM) using AB-8 macroporous resin. A major homogeneous polysaccharide, named FIP-Ⅱ, was purified from FIP through DEAE-650 M and Sephadex G-75 column chromatography. The structure of the FIP-Ⅱ was investigated through the combination of HPLC, GC, FT-IR, sequential acid hydrolysis, peroxide oxidation, Smith degradation, and NMR analysis. Then, the sulfated, phosphorylated, and carboxymethylated derivatives of FIP-Ⅱ, namely FIP-Ⅱ-S, FIP-Ⅱ-P, and FIP-Ⅱ-C, were prepared. Their structures were characterized by extensive analysis of chromatographic and spectroscopic methods including UV, HPLC, GC, FT-IR, Congo red, CD, SEM-EDX, XRD, TG, DTG, and DSC. Results of RSM showed that optimum purification conditions were elution flow rate 2.76 BV/ h, the sample concentration 2.03 mg/mL, and the elution volume was 1.26 BV. The average comprehensive score of purification was up to 76.28%. FIP-Ⅱ and its derivatives were heteropolysaccharides composed of different molar ratios of rhamnose, arabinose, xylose, mannose, glucose, and galactose, with a molecular weight of 775.64, 911.75, 1288.31, and 1013.61 kDa. The structure modification influences the solution conformation, surface morphology, crystalline nature, and thermal properties of the FIP-Ⅱ and its derivatives. Antioxidant activity tests showed that structure modification could significantly enhance the activity of the polysaccharides differently. It could be a potential ingredient in the functional food and pharmaceutical industry.

Extraction and characterization of arabinoxylans obtained from nixtamalized brewers' spent grains.

The processes to obtain value-added products from brewers' spent grain, a contaminant industrial waste, require alkaline non-ecofriendly pre-treatments. The arabinoxylans from brewers' spent grain were extracted by nixtamalization evaluating the extraction procedure, antioxidant capacity and molecular characteristics. The best arabinoxylans yields were those extracted with CaO at 100 °C and 25 °C (6.43% and 3.37%, respectively). The antioxidant capacity by 2,2-diphenyl-1-picrylhydrazyl assay of the arabinoxylans after thermal treatment and additional arabinoxylans after thermal treatment proteolysis were 434 and 118 mg TE/g, while by 2,20'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt assay the value was similar (380 μmol TE/g). The intrinsic viscosities and viscosimetric molecular weights were 69 mL/g and 13 kDa for arabinoxylans after thermal treatment, and 15 mL/g and 1.6 kDa for arabinoxylans after thermal treatment proteolysis, respectively. The protein and lignin contents were 3.1% and 6.4% for arabinoxylans after thermal treatment and, 0.9% and 4.6% for arabinoxylans after thermal treatment proteolysis, while their arabinose: xylose ratios were 0.39 and 0.36, with ferulic acid contents of 0.63 and 0.14 mg/g, respectively. Both products of arabinoxylans were molecularly identical by Fourier transform infra-red. Although the purity of the extracted arabinoxylans was improved with proteolysis, their intrinsic viscosity and viscosimetric molecular weight were affected. The extraction of arabinoxylans from brewers' spent grain by CaO nixtamalization alone or after additional proteolysis was successful to obtain purity and good antioxidant capacity.

High level xylitol production by Pichia fermentans using non-detoxified xylose-rich sugarcane bagasse and olive pits hydrolysates

Hemicellulosic sugars, the overlooked fraction of lignocellulosic residues can serve as potential and cost-effective raw material that can be exploited for xylitol production. Xylitol is a top platform chemical with applications in food and pharmaceutical industries. Sugarcane bagasse (SCB) and olive pits (OP) are the major waste streams from sugar and olive oil industries, respectively. The current study evaluated the potential of Pichia fermentans for manufacturing of xylitol from SCB and OP hydrolysates through co-fermentation strategy. The highest xylitol accumulation was noticed with a glucose and xylose ratio of 1:10 followed by feeding with xylose alone. The fed-batch cultivation using pure xylose, SCB, and OP hydrolysates, resulted in xylitol accumulation of 102.5, 86.6 and 71.9 g/L with conversion yield of 0.78, 0.75 and 0.74 g/g, respectively. The non-pathogenic behaviour and ability to accumulate high xylitol levels from agro-industrial residues demonstrates the potential of P. fermentans as microbial cell factory.

Effects of multi-mode divergent ultrasound pretreatment on the physicochemical and functional properties of polysaccharides from Sagittaria sagittifolia L

The aim of this study was to investigate the physicochemical and functional properties of polysaccharides from Sagittaria sagittifolia L. (SSP), extracted by the assistance of multi-mode divergent ultrasound (SSU), with different frequencies (20, 28, 40 kHz) and various combinations (20/28, 20/40, 28/40, 20/28/40 kHz). The results showed that, compared with hot water extraction, multi-mode divergent ultrasound assistance extraction (MDU) not only improved the yield of SSP (SSU-28/40 increased by 43.47%) with lower Mw and higher uronic acid content, but also changed its morphology (p < 0.05). In addition, all SSPs extracted by MDU are heteropolysaccharides with triple helix structure, which contain different molar ratios of rhamnose, arabinose, xylose, mannose, glucose and galactose. Moreover, these polysaccharides displayed higher foam capacity, foam stability, thermal stability, significant scavenging on DPPH, ABTS and hydroxyl radicals, and better inhibitory effects on HepG2 and MCF-7 cells in vitro. These results indicated that MDU may contribute to the degradation of polysaccharides, promote the transformation of monosaccharide, and improve the yield, solubility, antioxidant activity, and anti-tumor activity of SSP, suggesting that MDU has great potential application prospects in food, medicine, cosmetics and other fields.

Modified Monosaccharides Content of Xanthan Gum Impairs Citrus Canker Disease by Affecting the Epiphytic Lifestyle of Xanthomonas citri subsp. citri.

Xanthomonas citri subsp. citri (X. citri) is a plant pathogenic bacterium causing citrus canker disease. The xanA gene encodes a phosphoglucomutase/phosphomannomutase protein that is a key enzyme required for the synthesis of lipopolysaccharides and exopolysaccharides in Xanthomonads. In this work, firstly we isolated a xanA transposon mutant (xanA::Tn5) and analyzed its phenotypes as biofilm formation, xanthan gum production, and pathogenesis on the sweet orange host. Moreover, to confirm the xanA role in the impaired phenotypes we further produced a non-polar deletion mutant (ΔxanA) and performed the complementation of both xanA mutants. In addition, we analyzed the percentages of the xanthan gum monosaccharides produced by X. citri wild-type and xanA mutant. The mutant strain had higher ratios of mannose, galactose, and xylose and lower ratios of rhamnose, glucuronic acid, and glucose than the wild-type strain. Such changes in the saccharide composition led to the reduction of xanthan yield in the xanA deficient strain, affecting also other important features in X. citri, such as biofilm formation and sliding motility. Moreover, we showed that xanA::Tn5 caused no symptoms on host leaves after spraying, a method that mimetics the natural infection condition. These results suggest that xanA plays an important role in the epiphytical stage on the leaves that is essential for the successful interaction with the host, including adaptive advantage for bacterial X. citri survival and host invasion, which culminates in pathogenicity.