Characterization of Aureobasidium pullulans isolated from airborne spores in Thailand

Isolates from air in several locations in Thailand were identified as Aureobasidium pullulans PR with dark pigmentation (Loei province), A. pullulans SU with an unusual conidial apparatus (Chiangmai province), and A. pullulans CU with burgundy-red pigmentation (from a shady area in Bangkok). The internal transcribed spacer sequences of the rDNA of A. pullulans SU and A. pullulans CU confirmed that they were A. pullulans. Both A. pullulans CU and A. pullulans PR preferred 30 degrees C and pH 7.5 for exopolysaccharide (EPS) production, while A. pullulans SU preferred 25 degrees C and pH 6.5. All three isolates preferred glucose over sucrose and (NH(4))(2)SO4 over peptone for EPS production. Under optimal conditions, A. pullulans PR produced EPS yields of up to 0.225 g g(-1), followed by A. pullulans CU (0.185 g g(-1)) and A. pullulans SU (0.158 g g(-1)). Amylase activities were detected during the course of EPS production but gradually decreased as the EPS yields increased. IR spectra suggest that the EPS from these isolates was pullulan. EPS from the three isolates were partially sensitive to pullulanase.