Karynne Bernardine G. SiclotBS ChE-5 CHE 515N August 13, 2015

Critique: Production of L(+) lactic acid from cassava starch hydrolyzate by immobilized Lactobacillus delbrueckii

Biological fermentation to produce lactic acid is an attractive method compared to chemical synthesis because optically pure lactic acid (such as L(+) lactic acid) can be produced in biological fermentation. However, there are limitations in the use of biological method. The problems stated in the fermentation in a bioreactor involve washout of the cells, but immobilizing the cells can allow high concentration of the cells in the reactor.

The article discussed the advantages of using immobilized cells for the production of lactic acid. Aside from preventing washout of the cells, immobilization can also protect the cells from bacteriophages, contamination, and physic-chemical changes. The study utilized Lactobacillus delbreuckii for lactic acid fermentation and entrapping them in gel matrices.

The gel used to entrap the cells is easy to produce, but the concentration and type of alginate material to make the gel beads affect its properties. Therefore, the concentration and type of the alginate would depend on the cell to be immobilized. Optimization of the parameters to produce the gel beads with the desired properties to immobilize the particular strain of lactic acid bacteria was also discussed in the article. The parameters include concentration of alginate and CaCl2, initial cell concentration, curing time, bead size, agitation and incubation time of fermentation.

The gel beads can also be regenerated. The limit of regenerating the beads in the study was investigated by repeated batch fermentations. The results show that the gel beads can be reused for 6 batches of fermentation.

The use of immobilization gives more advantages in the production of lactic acid by biological fermentation. Selectivity, high yield, and lesser chances of contamination make immobilization a more preferred method in many fermentation processes.