Monday, July 27, 2009
P132

A Mathematical Model for the Production of D-Arabitol from Lactose by Kluyveromyces lactis

Tomoyuki Toyoda and Kazuhisa Ohtaguchi. Department of Chemical Engineering, Tokyo Institute of Technology, #464, S-1 bldg., 2-12-1, O-okayama, Meguroku, Tokyo, Japan, Tokyo, Japan

The waste water treatment for the industrial effluent from the process for ultra-filtration of cheese whey presents a problem of high loading of recalcitrant lactose. Studies on biological transformation of lactose in whey permit the production of foods, food supplements or clinically useful compounds. We have found the direct D-arabitol production from lactose by Kluyveromyces lactis, however, the properties of this microbiological reaction are not well understood. It has been reported that production of sugar alcohols by yeasts are enhanced by addition of stress. The objective of this study is to investigate effect of initial lactose concentration on D-arabitol production by K. lactis. Cells were cultivated in 2 mL medium in 20 mL test tubes, shaken at 200 rpm, at 303 K. The basal medium used in this experiment contained 190 g/L lactose and 40 g/L yeast extract. Initial concentration of lactose was changed ranging from 47.5 to 190 g/L. Of special interest is the initial lactose concentration which triggers D-arabitol production. D-arabitol was detected when initial lactose concentration was higher than 95 g/L. Highest D-arabitol concentration of 12.1 g/L was observed in the run with 190 g/L of initial lactose. This observation suggests that D-arabitol production of K.lactis might be the outcome of shifting-up of osmotic stress by lactose at the beginning of cell growth. A mathematical model for D-arabitol production by K.lactis was formulated. It was confirmed that the simulated data corresponded with the experimental data.

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