Utilização de resíduos do processamento de café (Coffea arabica L.) e de maracujá (Passiflora edulis Sims. f. flavicarpa Deg.) como substratos na produção de ácido cítrico por Aspergillus niger

Abstract

Coffee is one of the agricultural products of major economic importance in the Brazilian agribusiness. During the processing of grain residues are generated, which are arranged inadequate forms on the environment. During the processing of grain residues are generated, which are arranged in shapes unsuitable environment. When processed by wet, coffee generates waste as the mellow peel and wash water. The bark of passion fruit is composed of flavedo (part with color) and albedo (white part), which is rich in pectin, (vitamin B3), iron, calcium, and phosphorus. Improper disposal of waste processing of certain fruits, such as passion fruit, since it is grown on a large scale in most of Brazil implies studies for the use of this by-product, generating high value added products. This study was to evaluate and optimize the production of citric acid by Aspergillus niger in submerged fermentation using the composition of the culture medium, different proportions of coffee pulp extract and flour of passion fruit peel. The agro-industrial residues were analyzed for their content of total reducing sugars, soluble solids and pH, showing the increase that the passion fruit peel flour showed higher acidity and increase in sugar content compared to the mellow bark extract of coffee. A fermentation study using different variations of passion fruit peel flour and coffee pulp extract was performed. In the fermentation step used was isolated from Aspergillus niger (A. niger 00114). During fermentation, the levels consumed sugars were measured pH, fungal growth (biomass) and citric acid production. As a result, it was found that the maximum production of citric acid by the fungus was 10.21 (gL-1) on the 4th day of incubation at pH 3.44 for medium containing 70% syrupy coffee bark extract and 30 % of passion fruit peel flour, which is considered the most effective substrate in citric acid production compared to the others. After optimization of medium containing 70% of syrupy coffee husk extract and 30% of passion fruit peel flour, the maximum production of citric acid was 11.82 (g L -1) at pH 1.88 and occurred in the fourth day of incubation. Thus, there was an increase of 1.61 (gL-1) of citric acid compared to the same culture medium not optimized. Thus, through the optimization of the parameters is a key factor for the increase in the production of organic acids and enabled the detailed study of the influence of each variable on the optimized final product. Therefore, the use of such organic residues for the production of citric acid is possible.