Produção de pectinases por fermentação semisólida utilizando resíduo do maracujá como substrato.

Abstract

This research was developed with the objective of producing pectic enzymes using as substrate the residue of passion fruit and as fermentation agent a filamentous fungus of the Aspergillus niger strain mutant CCT 0916. Among the variables which influenced this process, the initial content moisture and the supplementation with a source of nitrogen (ammonium sulfate) was studied by means of a 22 factorial design. Through the characterization of the residue, it was confirmed that it contains levels of pectin and sugar propitious to the production of the enzymes. The production of the isotherms to 25, 30, 35 and 40 ºC furnished the values of moisture between 5.90 e 9.80% d.b. considered a range for a safe storage and water activities of 0.92 – 1.00 as the interval in which the microorganism can develop. The GAB model fitted adequately to the isotherms at the temperatures studied. According to BET classification, the curves were of type III, and according to Blahovec they were classified as type II. In relation enzymatic activity, the best results were obtained with 40% moisture and 1.0% nitrogen, reaching 250 U/g of fermented medium for pectin activity and 20.9 U/g for polygalacturonic activity, in 44 and 66 hours of fermentation respectively. The polygalacturonase produced in the raw enzymatic extract presented good thermal stability up to temperatures of 50oC. As for the study of stability according to pH variations, this enzyme remained stable in the pH range between 3.5 and 5.5 and was not detected anymore for pH values above 6.5.