Lactic acid production from hemicellulosic hydrolyzate by cells of Lactobacillus bifermentans immobilized in Ca-alginate using response surface methodology

Abstract

Consumption of hexoses/pentoses and production of lactic acid by Lactobacillus bifermentans were investigated in optimized culture medium and hemicellulosic hydrolyzates. The hydrolyzate used had the following composition (expressed in gL -1 ): xylose 50 ± 5 gL -1 ; glucose 18 ± 3 gL -1 ; arabinose 29 ± 5 gL -1 . The immobilization experiments were conducted with microbial cells entrapped in calcium alginate beads. The results indicate that maximum concentrations of lactic acid were produced after 54 h of fermentation. All glucose and arabinose in wheat bran hydrolyzate were consumed during fermentation. Only xylose was not completely consumed. The substrate consumption rate was 3.2 gh -1 , 1.9 gh -1 , 1.6 gh -1 respectively for glucose, arabinose, and xylose. The optimized culture condition gave a lactic acid concentration and metabolic yield of 62.77 gL -1 and 0.83 gg -1 . These parameters improved to 41.3 gL -1 and 0.47 gg -1 respectively, when cell free was used.

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Growth kinetic models of five species of Lactobacilli and lactose consumption in batch submerged culture

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