Valorization of passion fruit peel by-product: Xylanase production and its potential as bleaching agent for kraft pulp

Passion fruit peel is a by-product of the fruit industry. Like other agroindustrial by-products, it is generated in large amounts, possesses low commercial value, and is discarded as waste. This study aimed to explore the potential of Araucaria forest fungi to produce xylanases, using passion fruit peel as the substrate. About 65 fungal lineages were isolated from Araucaria forest soil and screened for xylanase enzyme production. Among these, a fungal strain, identified as Aspergillus flavus, showed high potential for xylanase production by using passion fruit peel as the sole substrate. Process optimization resulted in a 7.89-fold increase in enzyme activity. The xylanases were stable at 55-60 °C, over a broad pH range; these are characteristics desired for pulp biobleaching. Therefore, the potential of using A. flavus crude xylanases for bleaching kraft pulp was examined; the results show that these enzymes are potential bleaching agents, with a Kappa efficiency of 35.93%. To the best of our knowledge, this is the first study to show impressive yields of xylanases by using passion fruit peel by-product as carbon source. This kind of “waste valorization” can help to reduce the production cost of xylanase, as well as the environmental problems posed by inappropriate disposal.