Pullulan production by tropical isolates of Aureobasidium pullulans

Abstract

Tropical isolates of Aureobasidium pullulans previously isolated from distinct habitats in Thailand were characterized for their capacities to produce the valuable polysaccharide, pullulan. A. pullulans strain NRM2, the so-called "color variant" strain, was the best producer, yielding 25.1 g pullulan l(-1) after 7 days in sucrose medium with peptone as the nitrogen source. Pullulan from strain NRM2 was less pigmented than those from the other strains and was remarkably pure after a simple ethanol precipitation. The molecular weight of pullulan from all cultures dramatically decreased after 3 days growth, as analyzed by high performance size exclusion chromatography. Alpha-amylase with apparent activity against pullulan was expressed constitutively in sucrose-grown cultures and induced in starch-grown cultures. When the alpha-amylase inhibitor acarbose was added to the culture medium, pullulan of slightly higher molecular weight was obtained from late cultures, supporting the notion that alpha-amylase plays a role in the reduction of the molecular weight of pullulan during the production phase.

An aubasidan-like β-glucan produced by Aureobasidium pullulans in Thailand

“…During the last decade, a large number of isolates of A. pullulans have been isolated from different tropical habitats in various areas of Thailand [1][2][3]5 . Most of these strains produced pullulan with only a few exceptions, such as the strains NRRL 58539 and NRRL 58543.…”

“…Hence the effect of nitrogen source on the EPS production by NRRL 58539, NRRL 58543 and NRRL 58560 was investigated using Production Medium as previously described 3 . (NH 4 ) 2 SO 4 and NaNO 3 were used as the sole nitrogen source (equivalent to 0.13 g N/l) whereas sucrose was used as the sole carbon source (5% w/v, equivalent to 21.03 g C/l).…”

“…FT-IR was performed as previously described 3 . Ground EPS was mixed with KBr at a (w/w) ratio of 1:100.…”

“…Aureobasidium pullulans (De Bary) Arnoud is a saprophytic black yeast commonly found worldwide in a wide range of habitats, such as leaf surfaces, painted walls, African deserts, marine environs and even glacial and subglacial ice [1][2][3][4][5] . A. pullulans is of biotechnological interest since it produces a biodegradable poly-α-1,6-maltotriose based exopolysaccharide (EPS) called pullulan.…”

Biochemical and molecular characterization of a new pullulan producer Rhodosporidium paludigenum PUPY-06

“…Agitation also maintains both heat and mass transfer factors during fermentation. Agitation mode of cultivation has been reported best for pullulan production from A. pullulans [51][52][53][54] and R. bacarum [4] in shake-flask fermentations.…”