Pullulans produced by strains of Cryphonectria parasitica—I. Production and characterisation of the exopolysaccharides

Emerging Trends in Pullulan-Based Antimicrobial Systems for Various Applications

Global reports on multidrug resistance (MDR) and life-threatening pathogens such as SARS-CoV-2 and Candida cruris have stimulated researchers to explore new antimicrobials that are eco-friendly and economically viable. In this context, biodegradable polymers such as nisin, chitin, and pullulan play an important role in solving the problem. Pullulan is an important edible, biocompatible, water-soluble polymer secreted by Aureobasidium pullulans that occurs ubiquitously. It consists of maltotriose units linked with α-1,6 glycosidic bonds and is classed as Generally Regarded as Safe (GRAS) by the Food and Drug Administration (FDA) in the USA. Pullulan is known for its antibacterial, antifungal, antiviral, and antitumor activities when incorporated with other additives such as antibiotics, drugs, nanoparticles, and so on. Considering the importance of its antimicrobial activities, this polymer can be used as a potential antimicrobial agent against various pathogenic microorganisms including the multidrug-resistant (MDR) pathogens. Moreover, pullulan has ability to synthesize biogenic silver nanoparticles (AgNPs), which are remarkably efficacious against pathogenic microbes. The pullulan-based nanocomposites can be applied for wound healing, food packaging, and also enhancing the shelf-life of fruits and vegetables. In this review, we have discussed biosynthesis of pullulan and its role as antibacterial, antiviral, and antifungal agent. Pullulan-based films impregnated with different antimicrobials such as AgNPs, chitosan, essential oils, and so on, forming nanocomposites have also been discussed as natural alternatives to combat the problems posed by pathogens.

Application of microbial extracellular carbohydrate polymeric substances in food and allied industries

Extracellular polymeric substances (EPS) are biopolymers, composed of polysaccharides, nucleic acids, proteins and lipids, which possess unique functional properties. Despite significant strides made in chemical production processes for polymers, the niche occupied by exopolysaccharides produced by bacteria, yeast or algae is steadily growing in its importance. With the availability of modern tools, a lot of information has been generated on the physico-chemical and biological properties using spectrometric tools, while advanced microscopic techniques have provided valuable insights into the structural-functional aspects. The size of EPS generally ranges between 10 and 10,000 kDa. The wide spectra of applications of EPS as adhesives, stabilizer, gelling, suspending, thickening agent, and surfactants in food and pharmaceutical industries are observed. The health benefits of these EPS enable the improvement of dual function, added value, and green products. This review summarizes previous work on the structural composition, rheological and thermal behaviour, and biosynthetic pathways of EPS and bioprocesses developed for their production. This review also considers each of the above factors and presents the current knowledge on the importance and refinement of available downstream protocols and genetic engineering towards specific food applications, which can help to diversify their prospects in different food and allied industries.

Safflower (Carthamus tinctorius L.) polysaccharide attenuates cellular apoptosis in steroid-induced avascular necrosis of femoral head by targeting caspase-3-dependent signaling pathway

The present study aimed to investigate the effects of a purified polysaccharide (SPS) from the safflower in a cellular model of steroid-associated necrosis of the femoral head (SANFH), which was established in primary murine osteoblasts suffering dexamethasone pretreatment. After treatment with SPS (25, 50 and 100 μg/ml), the degree of necrosis induced by dexamethasone was significantly reduced in osteoblasts as evidenced by an increase of cell viability and a decrease of apoptosis in osteoblasts. Furthermore, pretreatment with SPS (25, 50 and 100 μg/ml) significantly attenuated the activation of caspase-3 and cleavage of PARP relative to the model control cells. The addition of caspase-3 inhibitor (Z-DEVD-FMK) in dexamethasone-treated osteoblasts resulted in the inefficiency of SPS for inhibiting cellular apoptosis. Dose-dependent increases in alkaline phosphatase (ALP) activity, collagen synthesis and mineralization were also observed in SPS-treated osteoblasts at 72 h. The present study demonstrates that SPS may alleviate dexamethasone associated osteonecrosis by inhibiting caspsae-3-mediated apoptosis and may provide an alternative treatment for SANFH.

Recent advances in polysaccharide bio-based flocculants

Natural polysaccharides, derived from biomass feedstocks, marine resources, and microorganisms, have been attracting considerable attention as benign and environmentally friendly substitutes for synthetic polymeric products. Besides many other applications, these biopolymers are rapidly emerging as viable alternatives to harmful synthetic flocculating agents for the removal of contaminants from water and wastewater. In recent years, a great deal of effort has been devoted to improve the production and performance of polysaccharide bio-based flocculants. In this review, current trends in preparation and chemical modification of polysaccharide bio-based flocculants and their flocculation performance are discussed. Aspects including mechanisms of flocculation, biosynthesis, classification, purification and characterization, chemical modification, the effect of physicochemical factors on flocculating activity, and recent applications of polysaccharide bio-based flocculants are summarized and presented.

Structural identification and immunostimulating activity of a Laminaria japonica polysaccharide

In the present study, a new water-soluble polysaccharide (LJP-11) was obtained from Laminaria japonica by anion exchange DEAE-cellulose chromatography and Sephacryl S-500 chromatography. The average molecular weight of this polysaccharide was estimated to be about 2.89×10(6) Da by high performance liquid chromatography system. Gas chromatography showed that LJP-11 was composed of arabinose, mannose and glucose in a molar ratio of 1.0:1.16:6.33. LJP-11 contains a long backbone consisting of (1→4)-β-D-GlcpAc, (1→4)-α-D-Glcp, (1→6)-β-D-Glcp and (1→3,6)-α-D-Manp. The 1-linked β-L-Araf was linked to the C-6 of (1→3)-α-D-Manp and the sulfate group was attached to the C-4 of (1→6)-β-D-Glcp. Pharmacological tests displayed that LJP-11 can stimulate macrophages to release NO, IL-6, TNF-α and IL-10 as well as the up-regulation of their gene expressions, indicating LJP-11 has beneficial effects on immunostimulation. Moreover, LJP-11 exhibited positive effects on the translocation of NF-κB p65 from cytoplasm to nucleus and the phosphorylation of IκBα, ERK1/2, JNK1/2 and P38 in macrophages. These results suggested that the activation of MAPK and NF-κB signaling pathways is one of the mechanisms responsible for the immunostimulating activity of LJP-11.

Schisandra polysaccharide evokes immunomodulatory activity through TLR 4-mediated activation of macrophages

Schisandra chinensis (Turcz.) Baill has been used in traditional Chinese medicine for centuries. Previous studies have shown that Schisandra polysaccharide (SCPP11) has robust antitumor activity in vivo. In this study, the immunomodulatory activity and mechanisms of action of SCPP11 were investigated further to reveal its mechanism of action against tumors. Results showed that SCPP11 increased the thymus and spleen indices, pinocytic activity of peritoneal macrophages, and hemolysin formation in CTX-induced immunosuppressed mice. Moreover, SCPP11 significantly increased immunoglobulin levels, cytokines levels in vivo and induced RAW264.7 cells to secrete cytokines in vitro. RAW264.7 cells pretreated with SCPP11 significantly inhibited the proliferation of HepG-2 cells. In addition, SCPP11 promoted both the expression of iNOS protein and of iNOS and TNF-α mRNA. TLR-4 is a possible receptor for SCPP11-mediated macrophage activation. Therefore, the data suggest that SCPP11 exerted its antitumor activity by improving immune system functions through TLR-4-mediated up-regulation of NO and TNF-α.

Multifunctional properties of polysaccharides from Dalbergia sissoo, Tectona grandis and Mimosa diplotricha

Three water-soluble polysaccharides were isolated and purified from the leaves of Dalbergia sissoo Roxb. (DSLP), bark of Tectona grandis L. f (TGBP) and seeds of Mimosa diplotricha var. diplotricha Sauvalle (MDSP). Antioxidant and moisture preserving activities of these three polysaccharides were investigated using in vitro methods. The antioxidant activities studied include superoxide (O2(*-)), 1,1-diphenyl-2-picrylhydrazyl (DPPH*), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS(*+)), hydroxyl (OH(-)), nitric oxide (NO*), N,N-dimethyl-p-phenylenediamine (DMPD(+)) radical scavenging activities, ferric ion (Fe(3+)) reducing ability, ferrous ion (Fe(2+)) chelating and lipid peroxidation activities. The study revealed higher activity of TGBP in all antioxidant assays than DSLP and MDSP. Further, the three polysaccharides showed effective moisture retention properties in comparison with hyaluronic acid and glycerol.

Development of suitable solvent system for downstream processing of biopolymer pullulan using response surface methodology

Downstream processing is an important aspect of all biotechnological processes and has significant implications on quality and yield of the final product. Several solvents were examined for their efficacy on pullulan precipitation from fermentation broth. Interactions among four selected solvents and their effect on pullulan yield were studied using response surface methodology. A polynomial model was developed using D-optimal design and three contour plots were generated by performing 20 different experiments and the model was validated by performing optimization experiments. The results indicated that lower concentration of ethanol in combination with the other three solvents has resulted in higher yield of polymer from fermentation broth and the optimized solvent system was able to recover 1.44 times more pullulan as compared to the conventional ethanolic precipitation method. These observations may help in enhancing efficiency of pullulan recovery from fermentation broth and also result in reduced cost of production for the final product.

Polysaccharide from Ganoderma atrum evokes antitumor activity via Toll-like receptor 4-mediated NF-κB and mitogen-activated protein kinase signaling pathways

Ganoderma atrum has been used as a traditional Chinese medicine for centuries. In this study, the antitumor activity of a novel G. atrum polysaccharide (PSG-1) was investigated in vitro and in vivo using S180 tumor-bearing mice. The results showed that PSG-1 significantly inhibited the proliferation of S180 via the activation of macrophages in a dose-dependent manner. PSG-1-primed macrophages exhibited a higher tumoricidal activity than untreated macrophages. Administration of PSG-1 significantly inhibited the growth of transplantable sarcoma S180-bearing mice and increased macrophage phagocytosis and the levels of cytokines and nitride oxide. Expression of Toll-like receptor (TLR) 4 in the membrane was markedly increased in PSG-1-treated groups, suggesting that it may be a possible receptor for PSG-1. PSG-1 also promoted the translocation of the p65 subunit of NF-κB from cytosol to nucleus and the degradation of IκBα. Moreover, the phosphorylation of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinases 1/2, and c-Jun N-terminal kinase in macrophages was improved by PSG-1 in a dose-dependent manner. Therefore, it is suggested that PSG-1 may elicit its antitumor effect by improving immune system functions through TLR4-mediated NF-κB and MAPK signaling pathways.

Fungal exopolysaccharide: production, composition and applications

Fungal exopolysaccharides (EPSs) have been recognized as high value biomacromolecules for the last two decades. These products, including pullulan, scleroglucan, and botryosphaeran, have several applications in industries, pharmaceuticals, medicine, foods etc. Although fungal EPSs are highly relevant, to date information concerning fungal biosynthesis is scarce and an extensive search for new fugal species that can produce novel EPSs is still needed. In most cases, the molecular weight variations and sugar compositions of fungal EPSs are dependent to culture medium composition and different physical conditions provided during fermentation. An inclusive and illustrative review on fungal EPS is presented here. The general outline of the present work includes fungal EPS production, their compositions and applications. An emphasis is also given to listing out different fungal strains that can produce EPSs.

Optimization of Ultrasonic-Assisted Extraction of Polysaccharides from Blackcurrant Using RSM

Ultrasonic-assisted extraction (UAE) method was applied for polysaccharides from blackcurrant and response surface methodology (RSM) was used to optimize the effects of processing parameters on polysaccharides yields. Three major independent variables such as ultrasonic power (W), extraction time (min), liquid to solid ratio (mL/g) were studied. The optimal extraction conditions of polysaccharides were determined as follows: ultrasonic power 402.2 W, extraction time 25.5 min, liquid to solid ratio 20.3:1 mL/g. Under a modified conditions (ultrasonic power 400W, extraction time 25 min, liquid to solid ratio 20:1 mL/g, the experimental yield of polysaccharides was 11.19%, which was agreed closely with the predicted value (11.24%).

Antioxidant and immunobiological activity of water-soluble polysaccharide fractions purified from Acanthopanax senticosu

A water-soluble polysaccharide obtained from Acanthopanax senticosus leaves (ASL), was fractionated by DEAE-Sepharose fast-flow column chromatography, and purified by Sephadex G-75 gel-permeation column chromatography. The characteristics of ASP-2-1 were determined by chemical analysis, high-performance capillary electrophoresis (HPCE), high-performance gel-permeation chromatography (HPGPC). The results show that ASP-2-1 contained 89.47% carbohydrate, 7.45% uronic acid, 2.16% protein and seven kinds of monosaccharides including rhamnose, xylose, glucose, mannose, arabinose, galactose and glucuronic acid in a molar ratio of 7.45:18.63:25.15:0.93:8.35:2.79:5.69, with an average molecular weight of about 14,573Da. Furthermore, the immunobiological and antioxidant activities, in vitro, of ASP-2-1 were evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and ferric-reducing antioxidant power assay (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH()), superoxide radical (()O(2)(-)) and hydroxyl radical (()OH) free radical-scavenging assay, respectively. The results showed that ASP-2-1 exhibited significantly higher immunomodulatory activities against the lymphocyte proliferation in vitro, pronounced reductive power (FRAP value: 785.1μM at 0.2mg/ml), strong hydroxyl radical (89.56% at 1mg/ml) scavenging activity, moderate superoxide radicals (65.32% at 1mg/ml) and DPPH radicals (68.9% at 1mg/ml) scavenging activities. ASP-2-1 should be explored as a novel and potential natural antioxidant and immunostimulating agent for use in functional foods or medicine.

Characterization of the molecular mass distribution of pullulans by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using 2,5-dihydroxybenzoic acid butylamine (DHBB) as liquid matrix

The performances of several matrices were investigated for the accurate determination of the molecular mass distributions of pullulans by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The ionic liquid matrix (ILM) 2,5-dihydroxybenzoic acid butylamine (DHBB) gave better and more reliable results than the crystalline matrices 2,5-dihydroxybenzoic acid (DHB) and 2,4,6-trihydroxyacetophenone (THAP). With the ILM it was possible to obtain spectra of pullulans up to more than 100 kDa, the highest molar mass reported thus far. Owing to the known advantages of liquid matrices providing better spot-to-spot reproducibility, an almost noise-free spectrum and constant baselines were obtained when working under optimized conditions. In particular, the extent of in-source fragmentation occurring with this group of fragile polymers was considerably and decisively reduced. Thus, a more reliable representation of the true oligomer and polymer distributions is experimentally attainable, especially for distributions with small polydispersity values. The maximum error in the measured distribution associated with fragmentation was estimated by model calculations describing the changes in the polymer distribution upon different probabilities of fragmentation events. These simulation results indicated that the data obtained by MALDI-TOFMS using the liquid DHBB matrix were of high reliability. In particular, the average value of the distributions, M(w), and the polydispersity were obtained with predicted uncertainties of between 3 and 15% depending on the width of the distribution and the mass of the polymers.

Response surface optimization of the critical medium components for pullulan production by Aureobasidium pullulans FB-1

Culture conditions for pullulan production by Aureobasidium pullulans were optimized using response surface methodology at shake flask level without pH control. In the present investigation, a five-level with five-factor central composite rotatable design of experiments was employed to optimize the levels of five factors significantly affecting the pullulan production, biomass production, and sugar utilization in submerged cultivation. The selected factors included concentration of sucrose, ammonium sulphate, yeast extract, dipotassium hydrogen phosphate, and sodium chloride. Using this methodology, the optimal values for concentration of sucrose, ammonium sulphate, yeast extract, dipotassium hydrogen phosphate, and sodium chloride were 5.31%, 0.11%, 0.07%, 0.05%, and 0.15% (w/v), respectively. This optimized medium has projected a theoretically production of pullulan of 4.44%, biomass yield of 1.03%, and sugar utilization of 97.12%. The multiple correlation coefficient 'R' was 0.9976, 0.9761 and 0.9919 for pullulan production, biomass production, and sugar utilization, respectively. The value of R being very close to one justifies an excellent correlation between the predicted and the experimental data.