Produção de ácido capróico a partir da fermentação anaeróbia de etanol e ácido acético

Abstract

The caproic acid has several industrial applications as biofuel precursor, dyer, lubrificant and additive in animal feed. This acid is commercially available from the petrochemical industry with generation of hazardous rejects. In this context, the anaerobic fermentation is an alternative with lower environmental impact, because depends on renewable resources for the production of this acid. The objective of this research was to evaluate the biological production of caproic acid through the carboxylic chain elongation process using ethanol and acetic acid as substrates in an upflow anaerobic sludge blanket reactor (UASB). The reactor has a diameter of 100 mm, total height of 1.35 m, fill volume of 13.8 L, and was operated at an organic loading rate of 3.5 gCOD.L-1.d-1(OLR3,5) e 5.0 gCOD.L-1.d-1(OLR5,0) with a constant hydraulic retention time (HRT) of 3.5 d and pH of 5.3. The production of caproic acid was assessed through high performance liquid chromatography (HPLC) using a refractive index detector. The chain elongation from acetic acid and ethanol was observed, with mean concentrations of 0.4 g.L-1 of caproic acid at the OLR3.5 and 1.6 g.L-1 at the OLR5,0 of caproic acid and efficiency yields of 11% at the OLR3.5 and 27% at the OLR5.0. These low yields are attributed to the accumulation of caproic acid in its undissociated form.