Contribution of proteases and cellulases produced by solid-state fermentation to the improvement of corn ethanol production

Abstract By cultivating a strain of Aspergillus tubingensis on agro-industrial by-products using solid-state fermentation technology, a biocatalyst containing more than 130 different enzymes was obtained. The enzymatic complex was composed mainly of hydrolases, among which a protease, an aspergillopepsin, accounted for more than half of the total proteins. Cell-wall-degrading enzymes such as pectinases, cellulases and hemicellulases were also highly represented. Adding the biocatalyst to corn mash at 1 kg/T corn allowed to significantly improve ethanol production performances. The final ethanol concentration was increased by 6.8% and the kinetics was accelerated by 14 h. The aim of this study was to identify the enzymes implicated in the effect on corn ethanol production. By fractionating the biocatalyst, the particular effect of the major enzymes was investigated. Experiments revealed that, together, the protease and two cellulolytic enzymes (an endoglucanase and a β-glucosidase) were responsible for 80% of the overall effect of the biocatalyst. Nevertheless, the crude extract of the biocatalyst showed greater impact than the combination of up to seven purified enzymes, demonstrating the complementary enzymatic complex obtained by solid-state fermentation. This technology could, therefore, be a relevant natural alternative to the use of GMO-derived enzymes in the ethanol industry

Regulation of lactic acid concentration in its bioproduction from wheat flour

International audienceLactic acid is an important molecule for biopolymer production that can be obtained by biological processes. This work deals with the control of the lactic acid concentration in its production bioprocess using wheat flour as substrate. An adaptive control strategy for the simultaneous saccharification, proteins hydrolysis and fermentation (SSPHF) continuous process of lactic acid production is proposed in order to regulate the lactic acid concentration to the target value. The latter is determined so that the lactic acid productivity is maximized. The control strategy effectiveness and robustness are illustrated by means of experimental results

Feedback linearizing controller coupled to an Unscented Kalman filter for lactic acid regulation

International audienceThis paper deals with the development of a control law for the regulation of the lactic acid concentration in its biotechnological production process. The studied system consists in a continuous bioreactor using wheat flour as raw material. Three reactions take place at the same time in the bioreactor: the gluten hydrolysis, the maltose saccharification and the glucose fermentation. This paper considers the optimization of the two last reactions. The optimal set point that maximizes the bioprocess productivity is first determined. Then, a state feedback linearizing controller is developed to maintain the lactic acid concentration at this optimal set point. Nevertheless, knowledge of all states variables is required for this kind of control law. Since the sole online measurement is the lactic acid concentration, robust and efficient estimators of the non-measured states have to be developed. In this paper, an Unscented Kalman filter (UKF) is proposed to estimate the biomass and substrates concentrations in the bioreactor and is then coupled with the feedback linearizing control law. Numerical simulations have been carried out to assess the control law performance

Adaptive Control of Lactic Acid Production Process from Wheat Flour

International audienceThe key feature of this paper is the development of a control strategy for the lactic acid production process from wheat flour in a continuous bioreactor. As lactic acid has inhibition effects on bacterial growth and its own production, the regulation of its concentration is required. In this paper, a control strategy is proposed in order to maximize the process productivity. First, the optimal setpoint is determined. Then, a controller based on a state-feedback linearizing control strategy is proposed to regulate the product concentration at its optimal value. The developed control law requires measurement or estimation of online state variables and a good knowledge of model parameters. In this paper the estimation of lactic acid production rate is proposed as an alternative to reduce the complexity of the control law. Different production rate estimators are studied and tested. Finally, the proposed control strategy results in a controller that involves the estimation of the production rate by a Kalman filter. The effectiveness of the developed strategy is illustrated by simulation results

Modeling the continuous lactic acid production process from wheat flour

International audienceA kinetic model of the simultaneous saccharification, protein hydrolysis, and fermentation (SSPHF) process for lactic acid production from wheat flour has been developed. The model describes the bacterial growth, substrate consumption, lactic acid production, and maltose hydrolysis. The model was fitted and validated with data from SSPHF experiments obtained under different dilution rates. The results of the model are in good agreement with the experimental data. Steady state concentrations of biomass, lactic acid, glucose, and maltose as function of the dilution rate were predicted by the model. This steady state analysis is further useful to determine the operating conditions that maximize lactic acid productivity