An economic evaluation of the fermentative production of lactic acid from wheat flour

A process for the fermentative production of lactic acid from whole-wheat f lour consisting of starch and bran containing nutrients is presented and an economical evaluation of the lactic acid production cost performed. Bottle necks were identified and alternative processes were evaluated and compared . The costs of raw material, the sodium hydroxide in the fermentation step, and the conversion of lactate to lactic acid using electrodialysis were fo und to contribute considerably to the total production cost. Performing the fermentation step as a batchwise step was economically better than continu ous fermentation. The lactic acid production cost can be reduced by lowerin g the pH and/or by recycling the sodium hydroxide produced by electrodialys is to the fermentor. Using higher wheat flour concentrations reduced the la ctic acid production cost and numerical optimisation of the process, with r espect to the wheat flour concentration, showed that the optimal concentrat ion corresponded to 116 g glucose/l, which resulted in a production cost of 0.833 US$/kg product. A Monte Carlo simulation of the total production cos t for this concentration when the investment and operational cost and the p rice of the raw material were varied showed that the probability that the p roduction cost could be lower than 0.90 or 1.0 US$/kg was 61% or 91%, respe ctively. (C) 2000 Elsevier Science Ltd. All rights reserved.