Sequential process of citric acid production in sugarcane bagasse by microbial consortium and ethanol fermentation from fungal extract

Abstract. Solid-state cultivation (SSC) may be defined as the microbial growth on solid supports. This process has been highlight in the chemical, food, pharmaceutical and agricultural with advantages compared to the submerged microbial growth. Citric acid, an important byproduct, can be obtained from the SSC from sugarcane bagasse by Aspergillus species, minimizing the cost of its production. Trichoderma reesei is a fungus with recognized activity of hydrolytic enzyme, leading to glucose release, which could be use in fermentation processes. Thus, the aim of this research was to evaluate the SSC of Aspergillus niger, Trichoderma reesei and consortium both for the citric acid production and glucose release from sugarcane bagasse. After this, evaluated ethanol fermentation by yeast Saccharomyces cerevisiae PE-02 from fungal extract of SSC. The results indicated the citric acid content around 405 mg L^-1 by fungal consortium, with vinasse as nutrient and moistening solution in the particles of sugarcane bagasse. On the other hand, 450 mg L^-1 of glucose in the fungal extract was obtained in 5 days of SSC by Trichoderma only. From fermentation this extract, there was a production of 0.22 g L^-1 of ethanol by yeast in 48 hours. Glucose was practically depleted leading the yield in ethanol near the stoichiometric. It can be suggested that there was no inhibitory component in fungal extract influencing the conversion of glucose to ethanol. The proposal SSC - fermentation for citric acid and ethanol production presents advantages when compared to conventional glucose release by acid hydrolysates of lignocellulosic material.