Optimization of Invertase from Aspergillus niger Grown on Low Cost Agricultural Wastes by Response Surface Methodology (RSM)
5 Aim: Response surface methodology (RSM) is an optimization technique that designs the most suitable 6 combination of media components and cultural conditions using statistical and mathematical principles for 7 enhanced production of bioproducts. This study explores the use of RSM in optimizing media components 8 and cultural conditions for the production of invertase by Aspergillus niger grown on potato peels (P1) and 9 pineapple peels (P2) under solid state fermentation. 10 Methodology: Chemical analyses of P1 and P2 were carried out using standard methods. Invertase 11 production was screened using Fehling solution test coupled with invertase activity assay. Reducing sugar 12 was estimated using dinitrosalicylic acid (DNSA) procedure. The RSM optimization design involved four 13 (4) independent variables (pH, temperature, pineapple peels concentrations, and potatoes peels 14 concentrations) at five (5) levels, screened through thirty (30) different experimental runs using central 15 composite design (CCD) 16 Results: Optimal fermentation conditions that yielded maximum invertase (321.4 U/mL) and biomass 17 (11.34 mg/mL) by A. niger was achieved with the combination of pH 9.0, temperature 35 C, pineapple 18 peels concentration 10% and potato peels concentration 50% The model used gave a predicted R Squared 19 of 0.2258. Negative "Predicted R squared" implies that the overall mean may be a better predictor of the 20 response than the current model. "Adequate precision" of 6.190 (check spacing) was obtained, showing that 21 the model can be used to navigate the design space. 22 Conclusion: This result has demonstrated the efficiency of RSM technique to optimize invertase 23 production from A. niger using potato and pineapple peels as substrates. The use of local substrates can 24 make invertase production economically attractive. 25 26