الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 155 |  |  |
| | | from | 155 | | |
Abstract
Dextranase is a useful enzyme which has many critical commercial and clinical applications. Twelve fungal isolates were isolated from the leaves of Ricinus communis and Delonix regia. By using the standard ITS rDNA sequencing analysis, the isolated dextranase-producing isolates were identified as Talaromyces sp. (EGY) and Aspergillus egyptiacus (LBC). The dextranase activity was quantitatively assayed using microplate colorimetric Somogyi-Nelson method. In the fermentation process, the maximum dextranase production by EGY isolate resulted using medium containing 1% dextran, peptone with initial pH of production medium was 7.4. Regarding A. egyptiacus isolate, the production condition investigations showed that the dextranase yield increased using dextran, yeast extract, and optimum initial pH of production media= 7.0. Ammonium sulphate fractionation was used to purify crude dextranases followed by Sephadex G-100 chromatography. SDS-PAGE analysis identified the MW of the purified enzymes from both isolates at 45 kDa. Regarding the purified dextranase, the optimum activity ranged from 37–40 °C and a pH of 6.0–8.0. At temperatures ranging from 30 to 70 °C and pH levels ranging from 4.0 to 8.0, purified dextranase remained extremely stable. The produced dextranase expressed remarkable biofilm inhibition activity in the standard strain P. aeruginosa PAO1, reducing 24h old-established biofilm by about 65–80 % and biofilm formation by 3–6%. In conclusion, these results suggested that EGY and LBC isolates showed high dextranase production with high thermal and pH stability and had a potent antibiofilm activity. These results would provide novel insights into the beneficial use of dextranase in the food, medicine, sugar industry, and other pharmaceutical fields.