Lactic acid production using the immobilized Rhizopusoryzae: effect of loofa sponge and mineral kissiris as the cell supports

Lactic acid-producing fungi, such as Rhizopusoryzae have received considerable attention because of their capabilities for the enzymatic production of this organic acid. Immobilization of cells offers several advantages such as higher productivity, operational stability and decreased contamination of the product by free cells. By following different cell-immobilization strategies, it is possible to considerably improve fermentation processes.Loofa sponge was used in the present experiment to study the R. oryzaePTCC 5263 immobilization. The mineral kissiris was also used for the fungal cell immobilization. In this study, the lactic acid production was determined when 1, 2 and 3 loofa pieces (2.5-cm diameter) or 5 g of kissiris pieces (1-cm diameter) were placed in 250-ml flasks containing 100 ml of soluble starch from potato and inoculated by adding the inoculum size of 3×105 spores/ml. The cultures were incubated at 30 oC with shaking speeds of 150 and 100 rpm, respectively, for pieces of loofa and kissiris. The immobilization of fungal cells on kissiris and loofa pieces was observed respectively after 48 and 72 hr of the inoculation. The highest concentration of lactic acid achieved in these immobilized-cells fermentation process was 5 g/L after 96 hr of fermentation time.