Search

International audience; Lactic 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.

Flours differing in water content of 10% (F10), 12% (F12), and 14% (F14) were stored for 16 weeks at 22, 32, and 45 degrees C. The major changes in lipids concerned the free fatty acids (increase) and the triglycerides (decrease). In all cases, the changes increased with increasing storage temperature and water content. After 16 weeks of storage, the losses in lipoxygenase (LOX) activity increased with increasing flour moisture and storage temperature from 10% for F10 at 22 degrees C to 100% for F14 at 45 degrees C. At the end of storage at 22 and 32 degrees C, the bread volumes decreased by 10 and 25%, respectively, with no statistical differences (P < 0.05) between the samples. At 45 degrees C, the volume losses were equal to 35, 46, and 61% for the F10, F12, and F14 samples, respectively. In the same time, the flour oxidative ability (oxygen uptake during dough mixing) increased for the F10 and F12 samples with increasing storage temperature, whereas it decreased for the F14 samples stored at 45 degrees C. Therefore, provided the residual LOX activity is sufficient (omission of the F14 samples stored at 45 degrees C), the flour oxidative ability increased during storage and is positively correlated to its oxidable PUFA content.

Purification of lactic acid obtained by the fermentation of cereal co-products was investigated (wheatflour with partial bran removing). Presence of proteins or arabino-xylans from wheat hemicellulose makes filtration difficult. Increasing pH up to 12 followed by 5000 g centrifugation and 15 kDa ultrafiltration allowed a limpid permeate to be obtained (, La purification d’acide lactique obtenu par fermentation d’une mouture de blé plus ou moins abrasé a été étudiée. La filtration des moûts est limitée par la présence de substances très colmatantes, protéinesou arabino-xylanes provenant des hémicelluloses du blé, Alcalinisation à pH 12, puis centrifugation et ultrafiltration à 15 kDa ont permis d’obtenir un perméat limpide, d’éviter le colmatage en profondeur de la membrane et de maintenir des flux de filtrat stables pendant plusieurs heures jusqu’à FRV 6. Les ions Ca2+et Mg2+ sont partiellement éliminés lors des étapes de précipitation et d’ultrafiltration. L’électrodialyse bipolaire a permis d’obtenir une solution contenant plus de 78 g.L-1 d’acide lactique avec un rendement faradique de 85 % et un flux de transfert d’environ 24 éq.h-1.m-2. La base utilisée pour l’alcalinisation pourra être récupérée à l’étape d’électrodialyse bipolaire (compartiment base) et recyclée.