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 their cellulolytic activities, among which 12 superior producers were quantitatively tested. Three Aspergillus spp. namely A5, A6 and A7 were found to be the best cellulolytic fungi, while both Aspergillus terreus NRRL260 and Phanerochaete chrysosporium NRRL6361 were found to be the best xylanase producers. On solid state fermentation (SSF) using pretreated rice 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-1 ds, respectively. On the other hand, Aspergillus terreus NRRL260 showed maximum xylanases activity of 804 U.g-1 ds. The recovered crude enzymes forming the crude enzyme mixture (CEM) was concentrated (LCEM), ammonium sulfate fractionated (PPE1), were semi-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 increase by 1.28, 2.08 and 2.78 for LCEM, PPE1 and PPE2, respectively. PPE2 achieved maximum degree of saccharification (DoS) at enzyme load ≥ 10 FPU, substrate concentration ≥ 5% and incubation period after 48 hr to be 85%, 87% and 88%, respectively.