Effect of sodium alginate concentration, bead diameter, initial pH and temperature on lactic acid production from pineapple waste using immobilized Lactobacillus delbrueckii

Batch fermentation of liquid pineapple waste to lactic acid was performed using immobilized Lactobacillus delbrueckii subsp. Delbrueckii ATCC 9646 under anaerobic condition for 72 h. Calcium alginate was used as the immobilization matrix and the effects of sodium alginate concentration, bead diameter, initial pH and temperature on cell growth, glucose consumption and lactic acid production were investigated. The results indicate that maximum concentrations of lactic acid were produced after 56 h of fermentation when 2.0% sodium alginate concentration was used. Maximum lactic acid production was also obtained with a 1.0 mm bead diameter at initial pH of 6.5 and temperature of 37 °C. Simultaneously, the growth parameters for L. delbrueckii in Ca-alginate beads at the various temperature and pH were determined so as to describe the cell growth and lactic acid production rates.