Factors affecting the fermentative lactic acid production from renewable resources1

The immobilization of whole cells: Engineering principles

Bioutilisation of whey for lactic acid production

The biosynthesis of ammonium lactate, a product of lactic acid fermentation was studied from corn and glucose at five different pH values of 5.4 to 7.8. In the glucose fermentations, a 100% conversion of substrate was obtained resulting in a maximum lactic acid production yield of 93.2%. The optimum pH for the maximum volumetric rate of lactic acid biosynthesis (1.56 g dm−3 h−1) was between 6.0 and 6.5. The corn fermentations were slower than the glucose fermentations with a resulting lactic acid yield of 67.5%. Hydrolysis of corn by enzymatic or chemical methods as well as the use of ammonium hydroxide for pH control increased both the final concentration and the rates of lactic acid production. An enhanced yield of more than 90% was finally obtained in the corn fermentations. A logistic model adequately described the kinetics of biomass growth, lactic acid production and sugar utilization in the glucose fermentations at different pH values. The dynamics of lactic acid formation in the corn fermentations were also successfully described by the developed model. The dependence of the model parameters on pH was investigated.

Kinetics of lactic acid fermentation on glucose and corn by Lactobacillus amylophilus

In lactic acid fermentation by Lactobacillus delbrueckii, the produced lactic acid affected the lactic acid productivity. Therefore, for the purpose of alleviating this inhibitory effect, an electrodialysis fermentation method which can continuously remove produced lactic acid from the fermentation broth was applied to this fermentation process. As a result, the continuation of fermentation activity was obtained, and the productivity was three times higher than in non-pH-controlled fermentation. In electrodialysis fermentation, the amount of produced lactic acid was 82.2 g/liter, which was about 5.5 times greater than that produced in non-pH-controlled fermentation. It was concluded that these good results were obtained on account of alleviating the lactic acid inhibitory effect by electrodialysis fermentation. However, the fouling of anion-exchange membranes by cells was observed in electrodialysis fermentation.

Novel Method of Lactic Acid Production by Electrodialysis Fermentation

Lactic acid was produced by viable Lactobacillus delbreuckii NRRL-B445 in a hollow fiber fermenter. Final cell densities in the fluid surrounding the fibers in the fermenter were apparently as high as 480 gms DW/L, and volumetric productivities reached 100 gms/L-hr lactic acid. The observed cell yields were appreciably lower than batch cell yields.

Lactic acid production by Lactobacillus delbreuckii in a hollow fiber fermenter

A method and apparatus for continuous cultivation of microbial, animal or plant cells, particularly bacteria for producing lactic acid, employing a reactor comprising at least two microporous walled hollow fibers (13, 14) having an open port at one end and a sealed port (15) at the other end. The mass transfer of nutrients to the cells in the reactor shell space (19) and of products from the cells is enhanced by convective currents between the first (13) and second (14) fibers which results in attainment of improved cell density and productivity of desirable cell products.

T. Bruce Vick Roy

Papers

Lactic acid production by Lactobacillus delbreuckii in a hollow fiber fermenter

Rapid production of biological products by fermentation in a densely-packed microbial membrane reactor.