Pullulan is a random coil glucan polymer produced by Aureobasidium pullulans. It is one of the commercially promising biopolymers frequently used in pharmaceutical, food, cosmetics industries, etc. The aim of present study was to isolate an efficient fungal strain producing melanin-free pullulan. The fungal strains were isolated from fresh and decaying leaves of plants and screened for pullulan production. Fungal isolate PUPY-06 was the best producer of pullulan (2.12%, w/v). Morphological studies revealed the oval and cylindrical shape of its cells, budding and presence of septate as well as pseudohyphae. Colonies of the isolate on agar plate cultures were beige to orange colored with smooth, mucoid and butyrous texture. Morphological and biochemical characterization established the fungal isolate as Rhodosporidium sp. 18s rRNA sequencing and phylogenetic analysis revealed the isolate to be Rhodosporidium paludigenum. Fourier transform infrared spectroscopy and nuclear magnetic resonance of crude pullulan confirmed its structural characteristics. Maximum production of pullulan was achieved after 7 days of cultivation in shake-flask fermentations. Agitation mode of cultivation supported the higher production of pullulan in comparison to the stationary mode. Rhodosporidium paludigenum PUPY-06 was found as a novel pullulan producing strain. This is first report on pullulan production by Rhodosporidium paludigenum PUPY-06.
Key words: Rhodosporidium paludigenum; 18s rRNA; Phylogenetic tree; Shake-flask fermentations; Pullulan; Nuclear magnetic resonance.
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