Inulinase production from a new inulinase producer, Penicillium oxalicum BGPUP-4

- Morphological and molecular characterization of the fungal isolate BGPUP-4 determined it to be Penicillium oxalicum.
- Thin layer chromatography confirmed the exoinulolytic nature of the enzyme produced by Penicillium oxalicum.
- Maximum enzyme was expressed after 5 days of cultivation in shake-flask fermentations.
- Agitation mode of cultivation in shake-flasks supported maximum inulinase production by Penicillium oxalicum BGPUP-4.
- Investigations carried out shows that Penicillium oxalicum BGPUP-4 may be a good candidate for inulinase production.

The present study was carried out for the isolation and characterization of an efficient inulinase producing fungal strain. Out of 31 fungal isolates, only 16 strains showed the hydrolytic zone surrounding the fungal growth on an inulin-rich medium. Screening of 16 inulolytic fungal strains was carried out based on activity of enzyme on inulin and sucrose and their I/S ratio. Fungal isolate BGPUP-4 shown maximum inulinase activity (11.06 IU/mL) after 5 days of cultivation and the corresponding I/S ratio was 2.64. This I/S ratio confirmed the inulinase nature of the enzyme. Thin layer chromatography and densitometer scanning of the hydrolysate were obtained after hydrolysis of inulin by inulinases from 5 fungal strains having high enzyme activity. Micromorphological and macromorphological characteristics of the fungal isolate BGPUP-4 exhibiting maximum enzyme activity, revealed it to be Penicillium oxalicum. Furthermore, 18S rRNA gene sequencing and phylogenetic analysis confirmed the identification of the fungal strain. Out of various carbon sources tested, lactose (2%) in combination with inulin (1.5%, as an inducer) showed a stimulatory effect on inulinase production (19.14 IU/mL). Agitation mode of cultivation in shake-flask fermentations, supported maximum inulinase production (38.52 IU/mL) after 5 days of incubation. This is the first report on inulinase production from Penicillium oxalicum.