A comparison study on the production and recovery of lactic acid by fermenting dairy by-products with P. acidilactici and Lb. delbrüeckii spp. bulgaricus
This paper provides a comparative study on the fermentative production of lactic acid (LA) by the novel Pediococcus acidilactici KTU05-7, previously isolated from rye sourdough, and the common dairy Lactobacillus delbrüeckii spp. bulgaricus using dairy by-products as a substrate. Lactic acid bacteria growth in different fermentation medium, v-d-galactosidase activity, lactose consumption, distribution of l(+)/d(−)-lactic acid isomers and LA purification using a system of membranes were also examined. The highest LA yield (1.9 g/g) was obtained fermenting the whey permeate for 24 h with the novel P. acidilactici. This strain also showed a better growth in whey permeate, a higher tolerance to low pH conditions and tended to produce mainly l(+)-lactic acid, compared to the standard L. bulgaricus. Furthermore, the proteolytic action of P. acidilactici simplified the membrane filtration procedure, and hindered the formation of protein aggregate in fermented broth as compared to L. bulgaricus. The findings of this research suggest that the Pediococcus acidilactici strain has a potential to improve the biotechnological production of LA from dairy industry waste and its recovery by membrane processes.