Pullulans produced by strains of Cryphonectria parasitica—II. Nuclear magnetic resonance evidence

A structure-functionality insight into the bioactivity of microbial polysaccharides toward biomedical applications: A review

Microbial polysaccharides (MPs) are biopolymers secreted by microorganisms such as bacteria and fungi during their metabolic processes. Compared to polysaccharides derived from plants and animals, MPs have advantages such as wide sources, high production efficiency, and less susceptibility to natural environmental influences. The most attractive feature of MPs lies in their diverse biological activities, such as antioxidative, anti-tumor, antibacterial, and immunomodulatory activities, which have demonstrated immense potential for applications in functional foods, cosmetics, and biomedicine. These bioactivities are precisely regulated by their sophisticated molecular structure. However, the mechanisms underlying this precise regulation are not yet fully understood and continue to evolve. This article presents a comprehensive review of the most representative species of MPs, including their fermentation and purification processes and their biomedical applications in recent years. In particular, this work presents an in-depth analysis into the structure-activity relationships of MPs across multiple molecular levels. Additionally, this review discusses the challenges and prospects of investigating the structure-activity relationships, providing valuable insights into the broad and high-value utilization of MPs.

Exploring the roles of amylopectin in starch modification with Limosilactobacillus reuteri 121 4,6-α-glucanotransferase via developed methods

Limosilactobacillus reuteri 121 4,6-α-glucanotransferase (GtfBΔN) modifies starch by cleaving (α1 → 4) linkages and introducing non-branched (α1 → 6) linkages to produce functional starch derivatives. Research has mainly focused on GtfBΔN converting amylose (linear substrate), whereas the conversion of amylopectin (branched substrate) has not been studied in detail. In this study, we used GtfBΔN to understand amylopectin modification and performed a set of experiments to analyze this modification pattern. The donor substrates were segments from the non-reducing ends to the nearest branch point in amylopectin as shown from the results of the chain length distribution of GtfBΔN-modified starches. Decreased and increased contents of β-limit dextrin and reducing sugars, respectively, during the incubation of β-limit dextrin with GtfBΔN indicated that the segments from the reducing end to the nearest branch point in amylopectin act as donor substrates. Dextranase was involved in the hydrolysis of the GtfBΔN conversion products of three different substrates groups, maltohexaose (G6), amylopectin, and G6 plus amylopectin. No reducing sugars were detected, therefore, amylopectin was not used as an acceptor substrate, and no non-branched (α1 → 6) linkages were introduced into it. Thus, these methods provide a reasonable and effective approach to studying GtfB-like 4,6-α-glucanotransferase in analyzing the roles and contribution of branched substrates.

Downstream processing and structural confirmation of pullulan - A comprehensive review

Pullulan is a microbial polymer, commercially produced from Aureobasidium pullulans. Downstream processing of pullulan involves a multi-stage process which should be efficient, safe and reproducible. In liquid-liquid separations, firstly cell free extract is separated. Cell biomass can be separated after fermentation either by centrifugation or filtration. Due to practically insolubility of pullulan in organic solvents, ethanol and isopropanol are the most commonly used organic solvents for its recovery. Pullulan can also be purified by chromatographic techniques, but these are not cost effective for the purification of pullulan. Efficient aqueous two-phase system can be used for the purification of pullulan. The current review describes the methods and perspectives used for solid-liquid separation, liquid-liquid separations and finishing steps for the recovery of pullulan. Techniques used to determine the structural attributes of pullulan have also been highlighted.

Pullulan based stimuli responsive and sub cellular targeted nanoplatforms for biomedical application: Synthesis, nanoformulations and toxicological perspective

With growing interest in polymers of natural origin, innumerable polysaccharides have gained attention for their biomedical application. Pullulan, one of the FDA approved nutraceuticals, possesses multiple unique properties which make them highly advantageous for biomedical applications. This present review encompasses the sources, production, properties and applications of pullulan. It highlights various pullulan based stimuli-responsive systems (temperature, pH, ultrasound, magnetic), subcellular targeted systems (mitochondria, Golgi apparatus/endoplasmic reticulum, lysosome, endosome), lipid-vesicular systems (solid-lipid nanoparticles, liposomes), polymeric nanofibres, micelles, inorganic (SPIONs, gold and silver nanoparticles), carbon-based nanoplatforms (carbon nanotubes, fullerenes, nanodiamonds) and quantum dots. This article also gives insight into different biomedical, therapeutic and diagnostic applications of pullulan viz., imaging, tumor targeting, stem cell therapy, gene therapy, vaccine delivery, cosmetic applications, protein delivery, tissue engineering, photodynamic therapy and chaperone-like activities. The review also includes the toxicological profile of pullulan which is helpful for the development of suitable delivery systems for clinical applications.

Studies on characteristics and anti-diabetic and -nephritic effects of polysaccharides isolated from Paecilomyces hepiali fermentation mycelium in db/db mice

Type 2 diabetes mellitus plagues many people in China and the world, and its nephritis complication is the leading cause of death for patients. Paecilomyces hepiali contained various functional components, especially polysaccharides, which possesses well pharmacological activities. In this study, polysaccharide purified from Paecilomyces hepiali fermented mycelium entitled PHEA was obtained, and its structure was systemically characterized using fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR). In C57BL/KsJ (BKS).Cg-Dock7^m +/+ Lepr^db/JNju mice (db/db mice), via detecting the alternations on biochemical criterions, pathological indicators and protein expressions related to nuclear factor-E2-related factor 2 (Nrf2) and nuclear factor-κB (NF-κB) signaling in serum and/or tissues including muscle, liver and kidney after 8-week PHEA administration, the hypoglycemic, hypolipidemic, and anti-diabetic nephropathic activities of PHEA were confirmed. The purified P. Hepiali polysaccharide with the anti-diabetic and -nephritic properties was first reported in this study via regulating Nrf2-meadited NF-κB signaling in db/db mice.

Pullulan – Biopolymer with Potential for Use as Food Packaging

The materials used in food packaging based on non-biodegradable synthetic polymers pose a serious threat of pollution to the environment. Hence, research is now focused on developing eco-friendly and biodegradable packaging obtained from natural polymers. Pullulan is a microbial exopolysaccharide, obtained on a commercial scale by the yeast-like fungus Aureobasidium pullulans. It is a water-soluble, non-toxic and non-mutagenic edible biopolymer with excellent film-forming abilities and adhesive properties. Furthermore, pullulan presents great potential to fabricate thin, transparent, odorless and tasteless edible films and coating used as packaging material. This review article presents an overview on the basic mechanical and barrier properties of a pullulan-based film. It also describes the modification methods applied in order to obtain multifunctional materials in terms of satisfactory physico-mechanical performance and antimicrobial activity for food packaging.