Optimization of inulinase production by a newly isolated Penicillium amphipolaria strain using solid-state fermentation of hardy sugarcane stems

A new producer of fungal inulinase Penicillium amphipolaria KAS 2555, has been isolated from the soil area of dead mangroves litter in Herikudru island, followed by the production and optimization of inulinase enzyme by solid-state fermentation (SSF) utilizing a cheap substrate – hardy sugarcane (Saccharum arundinaceum) stems. During the screening process, only P.amphipolaria KAS 2555 displayed a zone of hydrolysis on the inulin media. Thin-layer chromatography (TLC) confirmed the action pattern and the exoinulolytic nature of the inulinase enzyme. After 4 days of fermentation, 2.45 U/gds activity was obtained. The inulolytic nature of the inulinase was proven by obtaining 0.59 I/S ratio. The optimization of media was carried out to obtain a regression model using central composite design. Five media constituents viz., inulin, (NH₄)₂SO₄, K₂HPO₄, KH₂PO₄, and, NaCl were used for optimization. The coefficient of determination (R²) calculated was 0.9490 for the inulinase activity. An inulinase activity of 7.59 U/gds (3.1 times higher than non-optimized medium) was observed at optimal conditions: (g/gds) inulin- 0.1, (NH₄)₂SO₄- 0.002, K₂HPO₄- 0.1, KH₂PO₄- 0.02 and NaCl- 0.02.