Aiming to scale up and apply control and optimization strategies, currently is required the development of accurate plant models to forecast the process nonlinear dynamics. In this work, a mathematical model to predict the growth of the Kluyveromyces marxianus and temperature profile in a fixed-bed bioreactor for solid-state fermentation using sugarcane bagasse as substrate was built up. A parameter estimation technique was performed to fit the mathematical model to the experimental data. The estimated parameters and the model fitness were evaluated with statistical analyses. The results have shown the estimated parameters significance, with 95 % confidence intervals, and the good quality of process model to reproduce the experimental data.

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Process modeling can lead to of advantages such as helping in process control, reducing process costs and product quality improvement. This work proposes a solid-state fermentation distributed parameter model composed by seven differential equations with seventeen parameters to represent the process. Also, parameters estimation with a parameters identifyability analysis (PIA) is performed to build an accurate model with optimum parameters. Statistical tests were made to verify the model accuracy with the estimated parameters considering different assumptions. The results have shown that the model assuming substrate inhibition better represents the process. It was also shown that eight from the seventeen original model parameters were nonidentifiable and better results were obtained with the removal of these parameters from the estimation procedure. Therefore, PIA can be useful to estimation procedure, since it may reduce the number of parameters that can be evaluated. Further, PIA improved the model results, showing to be an important procedure to be taken. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:905-917, 2016.

BACKGROUND Solid‐state fermentation is a well‐known bioprocess. The development of a solid‐state fermentation reactor faces difficulties in controlling temperature gradients inside the bed. To understand this behavior, a good phenomenological model must be used. Furthermore, the model parameters must be obtained by a reliable and robust parameters estimation procedure, since often the model parameters are not available in the literature. RESULTS The heuristic particle swarm optimization (PSO) method was used to estimate the parameters of the reparametrized model through the minimization of a nonlinear‐square objective function, since it is less sensitive to initial guesses than derivative based methods. Statistical analyses were made to evaluate the parameter estimation quality. Also, simulations with the reparametrized model were performed. All the analyses have revealed the great accuracy of the proposed model, predicting with very small residuals (errors) several experimental data sets of a solid‐state fermentation process. CONCLUSION Parameter models reparametrization procedure can be a very useful mathematical tool to obtain accurate and reliable models with fewer parameters to be estimated, providing less parameters correlation and increasing the degrees of freedom to perform the statistical analysis. In addition, the particle swarm optimization was found to be a very robust and efficient parameter estimation method. © 2015 Society of Chemical Industry

In this work, an artificial neural network (ANN) was used to predict the final temperature of chicken carcasses in an industrial scale. For this purpose, temperatures of chicken carcasses were obtained in a slaughterhouse at the end of the cooling process. The variables considered to influence the temperature of carcasses were average carcass weight, prechiller and chillers velocities, prechiller and chillers average temperatures, the absence or presence of bubbles in prechiller and chiller and bubbles intensity, which were considered as input for the ANN. For training and validation of the feed forward neural network, the above inputs were combined to minimize the weighted sum of the squares of the residues, being tested 10 transfer functions, three training algorithms and two different architectures. The best result was obtained using an ANN composed of two hidden layer (10 nodes in each layer), radial bias as transfer function and gradient descent backpropagation algorithm for training. Using this architecture, the regression coefficient was 0.9265. Even with many variables affecting the industrial cooling process of the chicken carcasses, the ANN developed showed satisfactory fitting of the final temperature of chicken carcasses. This model can be further used for optimization purposes, improving the process quality of chicken carcasses as well as process profitability. PRACTICAL APPLICATIONThe model used in this study can be further used for control and optimization purposes, improving the process quality of chicken carcasses as well as process profitability.bs_bs_banner Journal of Food Process Engineering