Production optimization of Aspergillus niger naringinase by response surface methodology

Abstract

Citrus juice for export has a slight bitter taste which is characteristic and acceptable by the consumer but high levels of naringin reduce its quality and commercial value. Naringin (a flavonoid  linked to a rhamnose and glucose) is the main bitter component of several citrus fruits. The reduction in bitterness may be achieved by naringinase, an enzyme that degrades naringin. This study aimed the production of naringinase of Aspergillus niger by fermentation of low-cost substrates from agroindustry. The experiment was planned according to a 2³ factorial design which included three replications at the center point having as variables (g/L):   naringin (0.20; 0.30 and 0.40); soy bean molasses (0.35; 1.05 and 1.75 of total sugars) and sugar cane molasses (0.35; 1.05 and 1.75 of total sugars). Using the results of 144 hours of fermentation the statistical analysis and predictions were carried out. The statistical analysis showed that the significant variables for the production of naringinase were sugar cane molasses and soy molasses, as long as naringin was used at its lowest concentration. The predictive analysis showed a maximum value of 1.35U/mL could be achieved when naringin (0.25g/L), sugar cane molasses (1.75g/L) and soy bean molasses (1.75g/L) were used.  When the validity test was carried out a value of 1.344  (99.3% of prevision) was obtained.