Cell entrapment of Lactobacillus casei subsp. casei ATCC 39392 for lactic acid production

In this study, lactic acid production by repeated batch fermentation using cell entrapped methods was compared. Barium alginate beads, agar gel and polyurethane foam cubes were employed as carriers to immobilize Lactobacillus casei subsp. casei for the purpose of L [+]-lactic acid production. Increasing concentrations of lactic acid during fermentation were better tolerated by barium alginate entrapped cells. Alginate beads had a considerable effect on lactic acid production and reduced the fermentation time by half. The volumetric productivity with barium alginate and agar immobilized cells were 0.625 and 0.425 [g/lh] respectively, whereas it was 0.375 [g/lh for conventional free-cell fermentation. Beside biocompatibility, barium alginate immobilized cells exhibited good mechanical strength during repetitive fermentations and could be used in repetitive batch cultures for more than 40 days. The novelty of this study is lactic acid production by repeated batch fermentation with immobilized L. casei using polyurethane foam [PUF] in an economical culture medium composed of whey and corn steep liquor supplemented by glucose

Comparison of lactic acid isomers produced by fungal and bacterial strains

Many organisms produce lactic acid by fermentation, but most industrially important strains are from the genus Lactobacillus and Rhizopus oryzae. L[+]-Lactic acid is the only optical isomer for use in pharmaceutical and food industries because human body is only adapted to assimilate this form. In this research, six strains of Lactobacillus and four strains of R. oryzae [known as high producer] were examined for optical isomers of lactic acid. The production of lactic acid was improved and lactic acid produced in submerged media on rotary shaker incubator. The optical isomers of lactic acid were examined by L[+] and D[-] lactate dehydrogenase kit. All the R. oryzae strains tested produced only L[+] isomer of lactic acid. The highest fungal and bacterial producer strains were R. oryzae PTCC 5263, Lactobacillus plantarum PTCC 1058, L. Bulgaricus PTCC 1332 and L. delbruekii subsp delbruekii PTCC 1333. Lactobacilli strains produced combination of both optical isomers of lactic acid. Among them, L. casei subsp. Casei produced the low amount of D[-]-lactic acid [2%]. The optimum concentration of glucose for lactic acid production by R. oryzae and Lactobacillus strains were 180 g/l and 80-120 g/l, respectively