Continuous production of lactic acid in a cell recycle reactor

High-rate continuous production of lactic acid byLactobacillus rhamnosus in a two-stage membrane cell-recycle bioreactor

“…With greatly increased density of biocatalysts, i.e., microbial cells, the volumetric productivity of lactic acid could go up to 160 g L −1 h −1 as reported in the study of Ohleyer et al (1985), which is more than 20 times higher than that of the conventional batch and chemostat processes.…”

“…If the cell concentrations in the reports could be increased to 140 g/L, the performances would increase as shown at Figure 8b. About half of the data reported by Ohleyer et al (1985) showed greater productivities than the simulation; this is because a higher concentration of yeast extract was used and also, the data were taken when glucose concentration was above 7 g/L. It is noteworthy that there were only four results that obtained lactic acid concentration above 85 g/L with greater productivities than the simulation, which might be roughly reasoned from the difference in the strains employed (L. bulgaricus: ᭡, Mehaia and Cheryan, 1987;, Tejayadi and Cheryan, 1995) or, the data were taken before steady state (90 h operation time: ᭞, Xavier et al, 1995).…”

“…The results of the simulation studies and current experiments are presented in Figure 8 together with previous re- (7): solid line, b is equation (9); dashed line, b ‫ס‬ 0.1 g g −1 h −1 ; dotted line, b ‫ס‬ 0.38 g g −1 h −1 , and points are data from others' experiments: ᭺, Vick Roy, 1983;᭹, Ohleyer et al, 1985;᭝, Mehaia and Cheryan, 1986;᭡, Mehaia and Cheryan, 1987;ᮀ, Bibal et al, 1991;, Tejayadi and Cheryan, 1995;᭞, Xavier et al, 1995;᭢, OlmosDichara et al, 1997;ࡗ, Börgardts et al, 1998; छ, this work. In plot b, the data used in the plot a were modified to compare at the same cell concentration (140 g/L), for example, if a productivity value in plot a was obtained at 100 g/L cell, it was multiplied by 1.4 ‫ס(‬ 140/100) in plot b.…”

“…From this point, MCRB has an important problem to be tackled: The concentrations of lactic acid are significantly low when compared with batch processes where the lactic acid concentration above 120 g/L is easily attainable. Except for a report showing 117 g/L D(−)-lactic acid with a volumetric productivity of 84 g L −1 h −1 (Mehaia and Cheryan, 1987), all other MCRB operations resulted in lactic acid concentrations of less than 90 g/L and, moreover, most of them had concentrations below 60 g/L (Cheryan, 1998;Litchfield, 1996;Ohleyer et al, 1985). The microorganisms cannot grow above a certain range of lactic acid concentration and the MCRBs are run under continuous manner with continuous bleeding of cells to prevent the loss of fluidity that occurs when cell concentration goes too high.…”

Lactic Acid Production to Purification: A Review

“…If investment costs are high, the volumetric productivity is maximized by continuous operation (John et al 2007). A high volumetric productivity is achieved by a cell recycle system, which results in a high cell density with complete glucose conversion (Ohleyer et al 1985).…”