Culture conditions affect the chemical composition of the exopolysaccharide synthesized by the fungus Aureobasidium pullulans

• Published in: Journal of applied microbiology Vol. 107; no. 2; pp. 691 - 698
• Main Authors: Orr, D, Zheng, W, Campbell, B.S, McDougall, B.M, Seviour, R.J
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.08.2009; Blackwell Publishing Ltd; Blackwell
• Subjects: Ammonium Sulfate - metabolism; Ascomycota - growth & development; Ascomycota - metabolism; Aureobasidium pullulans; Biological and medical sciences; Bioreactors - microbiology; chemostat nitrogen source; Culture Media; Fermentation; Fundamental and applied biological sciences. Psychology; Glucans - metabolism; Magnetic Resonance Spectroscopy; Microbiology; Nitrates - metabolism; Nitrogen - metabolism; Polysaccharides, Bacterial - biosynthesis; Polysaccharides, Bacterial - chemistry; pullulan; pullulanase; Time Factors; Trisaccharides - metabolism; β-(1,3)-glucan; β-(1,3)-glucanase; pullulanase; Enzyme; Applied microbiology; β-(1,3)-glucanase; Nitrogen; α-Dextrin endo-1,6-α-glucosidase; Extracellular; Source; Glycosylases; Fungi; Glucan; Aureobasidium pullulans; Glycosidases; Aureabasidium pullulans; β-(1,3)-glucan; chemostat nitrogen source; Hydrolases; pullulan; Chemical composition; Fungi Imperfecti; Chemostat; Polysaccharide; Culture; Glucanase
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/j.1365-2672.2009.04247.x

To identify if culture conditions affect the chemical composition of exopolysaccharide (EPS) produced by Aureobasidium pullulans. In batch airlift and continuously stirred tank (CSTR) reactors the EPS produced with low (0·13 g l⁻¹ N) initial NaNO₃ or (NH₄)₂SO₄ levels contained pullulan, with maltotriose as its major component, similar to that synthesized in the airlift reactor with high (0·78 g l⁻¹ N) initial NaNO₃ levels. EPS produced by CSTR grown cultures with high (NH₄)₂SO₄ levels contained little pullulan, possibly because of a population shift from unicells to mycelium. This chemical difference may explain why total EPS yields did not fall as they did with cultures grown under identical conditions with high NaNO₃ levels, where the pullulan component of the EPS disappeared. EPS synthesized in N-limiting chemostat cultures of A. pullulans changed little with growth rate or N source, being predominantly pullulan consisting of maltotriose units. While the EPS chemical composition changed little under N-limiting conditions, high initial medium N levels determined maltotriose content and/or pullulan content possibly by dictating culture morphology. These results emphasize the requirement of all studies to determine EPS chemical composition when examining the influence of culture conditions on EPS yields.