OPTIMIZATION OF THE COMPOSITION OF THE MEDIUM FOR OBTAINING LACTIC ACID WITHLACTOBACILLUS HELVETICUS SSP. RHAMNOSUS NBIMCC 507
Goranov B., M.Angelov, I.Dobrev, G. Kostov, Z.Denkova
Microorganisms need an appropriate medium and cultivation conditions for their development and the synthesis of metabolites. The medium for obtaining lactic acid by free cells of Lactobacillus helveticus ssp.rhamnosus NBIMCC 507 has been modeled and optimized. The managing factors and the limits of their variation have been determined through single factor experiments and statistical analysis.Modeling and optimizing of the composition of the medium is done by orthogonal central composition plan. Based on the conducted optimization the content of the medium for obtaining lactic acid has been obtained (g/dm3): glucose - 70.4; meat extract - 17:07; yeast extract - 10.9; CH3COONa - 10; K2HPO4 - 0.25; KH2PO4 - 0.25; MgSO4.7H2O - 0.1; MnSO4.7H2O - 0.05; FeSO4 - 0.05. The maximum specific growth rate of the lactic acid bacteria during cultivation in a laboratory bioreactor (µm = 0.637h-1) and the constants of utilization of glucose and the accumulation of lactic acid in the cultural medium have been determined.
Poster
OBTAINING LACTIC ACID WITH IMMOBILIZED LACTIC ACID BACTERIA
Angelov M., Z.Denkova, G.Kostov, B.Goranov, I.Dobrev
The obtaining of lactic acid with immobilized cells is a recent trend. The usage of various matrices increases the concentration of cells in the working volume of the bioreactor and the yield of the final product. Immobilization of the lactic acid bacteria Lactobacillus casei ssp.rhamnosus NBIMCC 1013 and Lactobacillus helveticus ssp. rhamnosus NBIMCC 507 in the Ca-alginate and k-carrageenan has been carried out. The dynamics of the growth of the cells in the gel matrix for 60 h atcultivation temperature of 37 ºC have been monitored. It has been shown that immobilized lactic acid bacteria retain their activity during the fermentation process. It was found that cell immobilization reduces the fermentation time during cultivation in laboratory column bioreactor with a thick layer reaching a threefold higher concentration of lactic acid in the medium - 65 g/dm3 compared tofree cells. It has been shown that the cells embedded in the gel structures increase their number to 1016 cfu/g.
Poster
COMPARATIVE STUDY OF OBTAINING OF LACTIC ACID WITH FREE AND IMMOBILIZED CELLS OF LACTOBACILLUS CASEI SSP. RHAMNOSUS NBIMCC 1013
Angelov M., P.Dimitrova, B.Goranov, G.Kostov, Z.Denkova
In recent years research on the application of immobilized microbial cells through their inclusion in various gel structures is expanding.The obtaining of lactic acid by free and immobilized cells of Lactobacillus casei ssp.rhamnosus NBIMCC 1013 has been examined. Lactic acid bacteria are immobilized in Ca-alginate. Periodic fermentation processes in a laboratory bioreactor with agitation and in a column bioreactor with thick layer of immobilized biocatalysts have been carried out.The main process parameters such as pH, Eh, concentration of lactic acid have been monitored. Differences in the physiological status of the free and immobilized cells due to the presence of diffusion barrier formed by the matrix of the medium, have been observed.
Poster