Dialysis Continuous Process for Ammonium-Lactate Fermentation of Whey: Mathematical Model and Computer Simulation

Abstract

A mathematical model was developed to describe a dialysis process for the continuous fermentation of whey lactose to lactic acid, with neutralization to a constant pH by ammonia. In the process, whey of a relatively high concentration is fed into the fermentor circuit at a relatively low rate so that the residual concentration of lactose is low. The fernentor effluent contains ammonium lactate, bacterial cells, and residual whey solids and could be used as a nitrogenenriched feedstuff for ruminant animals. Only water is fed into the dialysate circuit at a relatively high rate. The dialysate effluent contains purified ammonium lactate and could be converted to lactic acid and ammonium sulfate for industry. The fermentation was specifically modeled as a set of equations representing material balances and rate relationships in the two circuits. Dialysis continuous fermentations, in general, were modeled by combining these equations and by using dimensionless parameters. The generalized model was then solved for the steady state and used to simulate the specific fermentation on a digital computer. The results showed the effects of various material and operational and kinetic parameters on the process and predicted that it could be operated efficiently.

Dialysis Continuous Process for Ammonium-Lactate Fermentation: Improved Mathematical Model and Use of Deproteinized Whey

“…Altogether, the results demonstrated the validity of the mathematical model, which then was used to guide experimental tests for the ammonium-lactate fermentation of deproteinized whey. The improved model predicted the same effects of changes in the various parameters on the process and the same regions for experimental tests as did the previous model (4).…”

“…Thus, by 4 weeks into the fermentation, the permeability factor decreased by 50%. Coulman et al (4) showed that a fl of 2.0 should be used for the process to obtain suitable relief from product inhibition.…”

“…A background for this development exists in studies of the fermentation using whole whey as the substrate. The fermentation can be managed as a batch process (18), continuous process (11), or dialysis continuous process (4,22). The latter process relative to the nondialysis processes enables the use of more concentrated substrate, is more efficient-in the rate of substrate conversion, and additionally produces a dialysate effluent of less concentrated but purer ammonium lactate.…”

“…In the studies reported here, a rate expression for bacterial growth was developed containing separate terms for substrate limitation and product inhibition. The expression was incorporated into a mathematical model of the dialysis continuous process generalized with dimensionless parameters so that it could be widely applied (4). The resulting improved set of equations was employed to simulate the fermentation on a digital computer, and the results were verified using previous experimental results with whole whey as the substrate (22).…”

Modelling Fed-Batch Fermentation Processes: An Approach Based on Artificial Neural Networks

“…This work aims to demonstrate that Artificial Neural Networks (ANNs) are adequate to this task, due to their features of massive parallel computing and representation, ability to learn, adaptability and generalization [4]. ANNs, and in particular Multilayer Perceptrons (MLPs) used in this case, are mainly characterized by the topology of connections between neurons, the training algorithm and the activation function [3,2]. The choice of which ANN will be used to represent a process depends on the characteristics of the problem in question [7].…”