Multi fungal cellulases produced on pretreated sugar cane bagasse and rice straw cooperative actions

Abstract

Twenty eight pre-identified fungal isolates and strains were tested qualitatively for theircellulolytic activities, among which 12 superior producers were quantitatively tested. ThreeAspergillus spp. namely A5, A6 and A7 were found to be the best cellulolytic fungi, whileboth Aspergillus terreus NRRL260 and Phanerochaete chrysosporium NRRL6361 werefound to be the best xylanase producers. On solid state fermentation (SSF) using pretreatedrice straw (RS), the Aspergillus spp. A5, A6 and A7 gave total cellulases (as FPase), exocellulases(as CMCase) and cellobiase (as β-glucosidase) activities of ≥ 16, 130 and 21U.g-1ds, respectively. On the other hand, Aspergillus terreus NRRL260 showed maximumxylanases activity of 804 U.g-1ds. The recovered crude enzymes forming the crude enzymemixture (CEM) was concentrated (LCEM), ammonium sulfate fractionated (PPE1), weresemi-purified by gel permeation on Sephadex G100 and finally lyophilized to powder form(PPE2). The resulting cellulases specific activities were 0.50, 0.68, 1.01 and 1.47 U.mg-1,respectively. Those purification and concentration steps resulted in purification fold increaseby 1.28, 2.08 and 2.78 for LCEM, PPE1 and PPE2, respectively. PPE2 achieved maximumdegree of saccharification (DoS) at enzyme load ≥ 10 FPU, substrate concentration ≥ 5% andincubation period after 48 hr to be 85%, 87% and 88%, respectively.