Modeling of growth during detoxification of coffee residues by filamentous fungi

Abstract

The modeling of the growth and detoxification of a mixture of coffee residues (MCR) by solid-state fermentation (SSF) from the quantification of metabolic CO₂ as an indirect method, growth stoichiometry solution, and monitoring of polyphenols is described. The SSF was carried out in Raimbault columns with Lentinus strigosus, Trichoderma harzianum and two strains of Aspergillus sp.; one isolated from barley straw (Aspergillus sp. ABS) and another from coffee residues (Aspergillus sp. ACR); the CO₂ was trapped in a 1.0 M NaOH solution. The solution of the equation gave the conversion factor 3.53 g of CO₂ per gram of biomass, and by the modified Gompertz equation, the modeling of biomass with R² values greater than 0.95; μ_max were 0.12 ± 0.01 h⁻¹ for L. strigosus, 0.20 ± 0.03 h⁻¹ for T. harzianum, 0.21 ± 0.01 h⁻¹ for Aspergillus sp. ABS and 0.42 ± 0.08 h⁻¹ for Aspergillus sp. ACR, however, RMSE values, indicate predictions with considered errors. Finally, detoxification was possible in 75.74 ± 6.07% with L. strigosus at 10 days, 56.13 ± 6.92%, and 50.34 ± 4.82% with T. harzianum and Aspergillus sp. ABS, respectively, at 4 days and 32.89 ± 3.17% with Aspergillus sp. ACR at 10 days. The biomass quantification and modeling strategy provides a new tool for the study of SSF, in addition, detoxification is described as consumption of polyphenols as a substrate.