T. Roukas et Cg. Biliaderis, EVALUATION OF CAROB POD AS A SUBSTRATE FOR PULLULAN PRODUCTION BY AUREOBASIDIUM-PULLULANS, Applied biochemistry and biotechnology, 55(1), 1995, pp. 27-44
The production of extracellular polysaccharides from carob pod extract
by Aureobasidium pullulans in batch fermentation was investigated. Op
timum conditions for polysaccharide productivity, polysaccharide yield
, and fermentation efficiency were: initial sugar concentration of 25
g/L, initial pH 6.5, and temperature 25-30 degrees C. A maximum polysa
ccharide concentration (6.5 g/L), polysaccharide productivity (2.16 g/
L/d), total biomass concentration (6.3 g/L), and polysaccharide yield
(30%) were obtained with inoculum at 10% (v/v), initial sugars in caro
b pod extract of 25 g/L, pH 6.5, and 25 degrees C. The highest values
of pullulan proportion (70% of total polysaccharides) and fermentation
efficiency (89%) were assumed at initial sugar concentration of 25 g/
L, pH 6.5 and 30 degrees C. Structural characterization of purified pu
llulan samples by monosaccharide and methylation analyses, C-13-NMR, a
nd pullulanase digestion combined with size-exclusion chromatography r
evealed the presence of mainly alpha-(1 --> 4) (68%) and alpha-(1 -->
6) (31%) glucosidic linkages; however, small amounts (<1%) of triply l
inked (1, 3, 4- and 1, 4, 6-Glc) glucose residues were detected. The m
olecular-size distribution and intrinsic viscosity of pullulan derived
from culture grown at pH 4.5 (30 degrees C) showed a higher molecular
weight than its counterpart obtained at pH 6.5 (30 degrees C).