Читать книгу Bioprospecting of Microorganism-Based Industrial Molecules - Группа авторов - Страница 40

Pullulan is a HoPS composed of glucose monomers as organized as maltotriose subunits linked by α‐(1,6) linkages. It is produced by fungus Aureobasidium pullulans intracellularly using UDP‐glucose as a precursor followed by export outside the cell [5]. Other fungi have also been reported to produce pulluan, e.g. Eurotium chevalieri, Cryphonectria parasitica, Cyttaria darwinii, and yeast Rhodotorula baracum [23]. Pullulan is a neutral polysaccharide, and its molecular weight can range between 10 and 3000 kDa, and this variability is dependent on its production conditions. Pullulan shares a similar composition with maltodextrin, but it possesses more α‐(1,6) linkages (30%) compared to the later (20%). The higher occurrence of α‐(1,6) linkages results in show digestibility of pullulan compared to starch and hence is used for low‐calorie food products [12].

Pullulan is a non‐gel forming polysaccharide, but it increases the viscosity of a solution, when in the aqueous state even in relatively low concentrations. Pullulan can maintain its viscosity even in high heat, changes in pH, and metal ions [33]. To improve the properties of pullulan, different chemical modifications have been made in pullulan such as small functional groups like carboxymethyl, sulfate, phosphate, acetate, and alkyl esters [34]. Pullulan is used to make capsule shells, tablet coatings, and edible flavored films due to its film‐forming properties. Pullulan has been used as a nontoxic food additive in Japan since 1976 and has been regarded as GRAS by US FDA [12]. When consumed, pullulan can alter the composition of intestinal microbiota, specifically stimulating the growth of bifidobacteria and hence acting as a prebiotic [35]. Recently, when phthalyl pullulan nanoparticle was treated with probiotic Lactobacillus plantarum, the production of antimicrobial peptide plantaricin increased and showed more significant inhibition of Escherichia coli and Lis. monocytogenes growth [36].