FERMENTATIVE PRODUCTION OF POLY(BETA-HYDROXYBUTYRIC ACID) FROM XYLOSE VIA L-LACTATE BY A 2-STAGE CULTURE METHOD EMPLOYING LACTOCOCCUS-LACTIS IO-1 AND ALCALIGENES-EUTROPHUS

A two-stage culture method employing Lactococcus lactis IO-1 and Alcaligenes eutrophus was developed for the production of polyhydroxyalkanoic acid (PHA) from xylose via L-lactate. In this culture method, xylose was converted into L-lactic acid and acetic acid by a culture oft. lactis IO-1, and the organic acids were then converted into PHA by a culture of A. eutrophus. Alcaligenes eutrophus grew at a specific growth rate of 0.61/h; however, the growth rate decreased as the lactate concentration in the medium increased. When the supernatant of the IO-1 culture broth containing 10-g/L L-lactate was used as a medium for A, eutrophus in batch culture, the cell concentration increased to 8.5 g/L in 24 h and 55% (w/w) of the content of the cells was found to be poly(beta-hydroxybutyric acid), P(3HB). Furthermore, fed-batch culture of A, eutrophus was carried out with feeding of L-lactic acid to maintain the L-lactate concentration around 3.0 g/L. As a result, 41.0 g/L of cells and 28.7 g/L of P(3HB) were produced after 17 h of cultivation.