A search for fungal isolate with higher mannanase activity indicated that the local isolate Penicillium chrysogenum appeared as the most active one. Penicillium chrysogenum mannanase was eluted as one band near 30 kb by means SDS-PAGE at one step purification. Immobilization of the mannanase by entrapping this enzyme preparation in calcium alginate beads was carried out. The optimum temperature for free and immobilized form unchanged (50 ºC).The optimum pH of the free enzyme was 6 while the immobilized form achieved it at pHs range 6-6.5. At 70 º C the immobilized form could retain 41% of its activity after 180 min, while the free enzyme lost 88% of its original activity at the same time. The immobilization process reduced the activating energy from 21.36 kcal mol−1 to 17.79 kcal mol−1. Also, it was prolonged the half-lives and D values remarkably in compared to the free enzyme. Shelf stability study indicated that the immobilized mannanase was stable for a long period at 4 °C retaining 90% of the activity after 60 days. Bioconversion of locust bean gum (LBG) and yeast mannan by partially purified mannanase (PPM) was similar (41%) for free PPM and 23% for the immobilized form. The prebiotic activity of mannooligosaccharides (MOS) are comprising bio-converted samples of LBG and yeast mannan towards the probiotics Lactobacillus casei, Lactobacillus helveticus and Lactobacillus reuteri. Noteworthy is the highest prebiotic activity (prebiotic index 247) was recorded for MOS (of LBG) towards L. helveticus.
Key words: Penicillium chrysogenum, Mannanase, Immobilization, Mannooligosaccharides, Prebiotic activity.
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