Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

PP-V-5THE PROCESS FOR PRODUCING ORGANIC ACIDSBY MEMBRANE BIOREACTOR SYSTEMI.V. Ilushka, V.V. Kolbakov*, V.F. ShvetsD.I. Mendeleev University of Chemical Technology of Russia, Chair of PetrochemicalSynthesis, 9 Miusskaya Square, Moscow, 125047, Russia,tel/fax: +7(499)978-95-54, e-mail: agro3000@inbox.ru*Nordbiochem Ltd., Kuuse 2, Põlva, 63303 Estonia, e-mail: info@nordbiochem.euIntroductionLactic acid has been manufactured by employing the batch-type fermentation processwhich comprises the steps of culturing lactic acid bacteria for more than 60 hours afterinoculation and isolating lactic acid from the culture medium. The batch process has anadvantage of high-concentration lactic acid production of over 120 g/L, though it has revealeda critical shortcoming of low volumetric productivity of less than 5 g/L/h. To compensate forthe low productivity, the fermentation volume is enlarged, which in turn increases the cost forthe construction of fermentation facilities and the maintenance of the facilities. As analternative approach to overcome the low productivity of batch-type fermentation process,cell-recycling process by which microorganisms are concentrated in a fermenter to increasethe productivity, has been suggested.Results and conclusionsAccording to present experiments, the lactic acid and other organic acids can be producedin a simple and inexpensive manner, so as to eliminate the disadvantages of the priorprocesses discussed above. It has been surprisingly found, that if to create such conditions atwhich growth rate of cells is minimal but sufficient for replacement cells death, in this casedecrease of the specific consumption of carbohydrates per unit of lactate is take place.The growth rate of cells can be reduced by increase of temperature and decrease of pH upto critical and supercritical values for each microorganism and as well by decrease of amountsnutrients fed into the fermenter and by use of additives bacteriostatics.It has been surprisingly found, that for each microorganism there are optimal conditions -temperature, рН, amounts of nutrients and bacteriostatics fed into the fermenter, at whichgrowth rate of cells is minimal but sufficient for replacement cells death.Preferably, the optimal growth rate of cells is reached by combination of temperature, рН,by amount of used nutrients and bacteriostatics fed into the fermenter.Concentration of cells of microorganisms has been reached about 100 g/L (dried cellweight) and more, in the membrane recycle bioreactor system. With combinations ofparametres described above, we can get volumetric productivity more then 100 g/L/h.466