RESUMO
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