Produção de ácido cítrico por Botryosphaeria ribis EC-01 em fermentação submersa utilizando resíduos agroindustriais

Abstract

Citric acid is used in many industrial processes, being mostly used in the food industry, due to its biodegradable, water¬soluble, non¬toxic, antioxidant, acidulating and flavoring properties. Currently, its industrial production is carried out by fermentation using filamentous fungus Aspergillus niger and sugarcane molasses as substrate. However, the increasing industrial demand for this acid requires the development of more efficient of production routes. This study aimed to evaluate the citric acid production by filamentous fungus Botryosphaeria ribis EC¬01 using agroindustrial residues such as malt, yeast extract, soybean cake, glycerol and sugarcane molasses. There are no reports in the literature that explores the capacity of B. ribis EC¬01 for the production of citric acid. After selecting the variables that positively influenced the production of this acid, 2 3 rotational central composite designs were developed. Citric acid was quantified by spectrophometric method using trichloroacetic acid, acetic anhydride and pyridine at 420nm and 37ºC for 30 min. Soybean cake and sugarcane molasses enhanced the production of citric acid by B. ribis EC¬01, reaching 5,75 mg mL¬1 , with 14 % (w/v) soybean cake in 24 h, and 3,41 mg mL¬1 with 14 % (w/v) sugarcane molasses in the period of 120 h. A factorial design, considering time (20 ¬ 120 h) and the concentrations of soybean cake and sugarcane molasses (0 ¬ 20 % w/v), was evaluated, and this first model was predictive. From the responses obtained, a second factorial design was developed using time (13 – 63 h), soybean cake (15 ¬ 25 %, w/v) and sugarcane molasses (20 ¬ 40 %, w/v). The optimal conditions for the production of citric acid by B. ribis EC¬01 were determined (R2 = 0.85) and the optimal values for time, soybean cake and sugarcane molasses were 13 h, 25 % (w/v) and 35 % (w/v), respectively. The model was validated obtaining citric acid production of 10.01 ± 0.07 mg mL¬1 of, which is very close to the predicted value of 11.79 mg mL¬1 . The results showed that B. ribis EC-01 filamentous fungus has potential to produce citric acid by submerged fermentation using soybean cake and sugarcane molasses agroindustrial residues at times shorter than those reported in the literature, which makes the process economically viable.