Abstract
Response surface methodology was used to derive a prediction model for organic acids production by anaerobic acidogenic fermentation of cellobiose, using a mixed culture immobilized on γ-alumina. Three parameters (substrate concentration, temperature, and initial pH) were evaluated. In order to determine the limits of the parameters, preliminary experiments at 37 °C were conducted using substrates of various cellobiose concentrations and pH values. Cellobiose was used as a model sugar for subsequent experiments with lignocellulosic biomass. The culture was well adapted to cellobiose by successive subculturing at 37 °C in synthetic media (with 100:5:1 COD:N:P ratio). The experimental data of successive batch fermentations were fitted into a polynomial model for the total organic acids concentration in order to derive a predictive model that could be utilized as a tool to predict fermentation results when lignocellulosic biomass is used as a substrate. The quadratic effect of temperature was the most significant, followed by the quadratic effect of initial pH and the linear effect of cellobiose concentration. The results corroborated the validity and effectiveness of the model.
Highlights
IntroductionAnaerobic digestion involves four steps: (1) the breakdown of organic compounds into soluble oligomers; (2) further hydrolysis and fermentation to produce mainly organic acids (acidogenesis); (3) acetate production (acetogenesis); and (4) methane and carbon dioxide production (methanogenesis), which is the most energy and time-consuming step [10,11]
In the case of anaerobic acidogenic fermentation, the results showed that, at selected process conditions, and modes of operation, the anaerobic acidogenesis can lead to products with different compositions of organic acids and ethanol, which allows the possibility to produce different types of ester-based new generation biofuels
The aim of the present work was to derive a predictive model based on response surface methodology, which would be utilized as a tool to predict fermentation results when pretreated lignocellulosic biomass is used as a substrate
Summary
Anaerobic digestion involves four steps: (1) the breakdown of organic compounds into soluble oligomers; (2) further hydrolysis and fermentation to produce mainly organic acids (acidogenesis); (3) acetate production (acetogenesis); and (4) methane and carbon dioxide production (methanogenesis), which is the most energy and time-consuming step [10,11]. Organic acids such as acetic, propionic, isobutyric, butyric, isovaleric, and valeric acid, produced during the acidogenesis step, may be used among other applications for the production of ester-based fuels similar to biodiesel. This approach has been previously proposed as a cost-effective and environmentally friendly alternative [6,7,8,9,12,13]; further research is needed on efficient and cost-effective esterification, separation, and purification processes
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