Avaliação do potencial e modelagem cinética da produção de ácidos carboxílicos a partir de resíduos agroindustriais tratados anaerobiamente

Abstract

The massive generation of wastes from agroindustry is one of the greatest challenges nowadays in a context of high global demand for energy and materials. In this sense, anaerobic digestion (AD) can be adapted to the biotechnological production of carboxylic acids (CA), which are building block chemicals with wide usage on industrial segments. The evaluation of the potential use of agroindustrial wastes as substrates and the study of the kinetic modeling of fermentation are very important for the development of the carboxylic platform. The present work aimed to evaluate the potential and performing kinetic modeling of CA production from dairy wastewater (DW) and residual glycerol (RG) from biodiesel production via acidogenic fermentation using mixed biomass as inoculum. The fermentation assays of production potential tests of carboxylic acids (PPCA) were performed in batch reactors (250 mL reactional volume and 50 mL headspace), which were inoculated with an anaerobic sludge from brewery wastewater in a theoretical food/microorganism (F/M) ratio of 0.60 g. COD g VSS-1 using DW and RG as substrates. The reactors were incubated at 35 °C and 120 rpm until the total organic matter consumption was observed. From the experimental data, kinetic modeling of each substrate was carried out with models previously described in the literature. The results showed that both substrates had high acidification potential, since the results to DW assays were 0.66 mg acids per mg COD available, corresponding to 0.83 mg COD acids per mg COD available while the results with the RG tests were 0.62 mg acids per mg COD available, corresponding to 0.82 mg COD acids per mg COD available. The First Order with Residual model was found to be the best model to describe the hydrolysis of particulate organic matter, the consumption of soluble substrate and the production of COD in the form of acids. The Logistic and the Fitzhugh models were the most suitable for the consumption of soluble substrate and the production of COD in the form of acids from RG, respectively. It was observed that there is a variation among the best models to describe the individual production of CA. Thus, the use of agroindustrial wastewaters as substrates for acidogenic fermentation using microbial consortium as inoculum is an environmentally friendly approach to manage wastes and to promote the sustainable biotechnological prospection of CA.