title: Response surface optimization for enhanced production of cellulases with improved functional characteristics by newly isolated Aspergillus niger HN-2.
abstract: Fungi isolated from partially decayed wood log samples showing characteristic diversity for spore colour, colony morphology and arrangement of spores were assessed for cellulolytic enzyme production. Isolates showing a cellulolytic index of ≥2.0 were assayed for filter paper (FP) cellulase and β-glucosidase (BGL) production. Molecular characterization confirmed the identity of the selected cellulolytic isolate as a strain of Aspergillus niger (A. niger HN-2). Addition of 2 % (w/v) urea enhanced FP and BGL activity by about 20 and 60 %, respectively. Validation studies conducted at parameters (29 °C, pH 5.4, moisture content 72 % and 66 h) optimized through response surface methodology in a solid-state static tray fermentation resulted in FP, BGL, cellobiohydrolase I (CBHI), endoglucanase (EG), xylanase activity and protein content of 25.3 FPU/g ds, 750 IU/g ds, 13.2 IU/g ds, 190 IU/g ds, 2890 IU/g ds and 0.9 mg/ml, respectively. In comparison, A. niger N402 which is a model organism for growth and development studies, produced significantly lower FP, BGL, CBHI, EG, xylanase activity and protein content of 10.0 FPU/g ds, 100 IU/g ds, 2.3 IU/g ds, 50 IU/g ds, 500 IU/g ds and 0.75 mg/ml, respectively under the same process conditions as were used for A. niger HN-2. Process optimization led to nearly 1.8- and 2.2-fold increase in FP and BGL activity, respectively showing promise for cellulase production by A. niger HN-2 at a higher scale of operation. Zymogram analysis revealed two isoforms each for EG and cellobiohydrolase and three isoforms for BGL. Crude cellulase complex produced by A. niger HN-2 exhibited thermostability under acidic conditions showing potential for use in biofuel industry.
authors.affiliation: Central Institute of Post-Harvest Engineering and Technology, P.O. PAU, Ludhiana, 141 004, India, hari_manu@yahoo.com.
authors.forename: Harinder Singh
authors.initials: HS
authors.lastname: Oberoi
authors.forename: Rekha
authors.initials: R
authors.lastname: Rawat
authors.forename: Bhupinder Singh
authors.initials: BS
authors.lastname: Chadha
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D002480:Cellulase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry / Q000378:metabolism; D004795:Enzyme Stability; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D013172:Spores, Fungal / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D014934:Wood / Q000378:metabolism / Q000382:microbiology*
chemical_list: D003470:Culture Media; D005656:Fungal Proteins; D002482:Cellulose; D002480:Cellulase