Xylitol formation by Candida boidinii in oxygen limited chemostat culture

Summary Production of xylitol by Candida boidinii NRRL Y-17213 occurs under conditions of an oxygen limitation. The extent to which substrate is converted to xylitol and its coproducts (ethanol, other polyols, acetic acid), and the relative flow rates of substrate to energetic and biosynthetic pathways is controlled by the degree of oxygen limitation.With decrease in oxygen concentration in the inlet gas, for a constant dilution rate of 0.05 1/h. the specific oxygen uptake rate decreased from 1.30 to 0.36 mmol/gh Xylitol was not produced at specific oxygen uptake rates above 0.91 mmol/gh. Upon shift to lower oxygen rates, specific xylitol production rate increased more rapidly than specific ethanol production rate:Nomenclature D dilution rate (1/h) - DOT dissolved oxygen tension (%) - m_o2 maintenance coefficient (mmol O₂/g cell mass h) - q_o2 specific oxygen uptake rate (mmol O₂/g cell mass h) - q_s specific xylose uptake rate (g xylose/g cell mass h) or (mmol xylose/g cell mass h) - q_x specific xylitol production rate (g xylitol/ g cell mass h) or (mmol xylitol/ g cell mass h) - q_e specific ethanol production rate (g ethanol/ g cell mass h) or (mmol ethanol/ g cell mass h) - q_CO2 specific carbon dioxide production rate (mmol CO₂/g cell mass h) - S xylose concentration (g/1) - Y_cm/s cell mass yield coefficient, (g cell mass/mmol xylose) or (g cell mass/ g xylose consumed) - Y_cm/O2 cell mass yield coefficient, (g cell mass/mmol O₂) - Y_X/S xylitol yield coefficient (g xylitol/g xylose consumed) - Y_x/O2 xylitol yield coefficient (g xylitol/mmol O₂) - Y_e/s ethanol yield coefficient (g ethanol/g xylose consumed) - OUR oxygen uptake rate (mmol O₂/1h) - specific growth rate (1/h)