Butyric Acid Fermentation in Xylose and Glucose by Clostridium tyrobutyricum

Abstract

The objective of this study was to understand the effect of different concentrations of xylose and glucose on butyric acid production by Clostridium tyrobutyricum. C. tyrobutyricum was cultured in a medium containing xylose, glucose, or mixtures of xylose and glucose as the main carbon source. The butyric acid concentration increased from 3.5 to 16.3 g/L in the xylose media, and from 2.6 to 27.0 g/L in the glucose media when the initial sugar concentration increased from 5 to 75 g/L. The yield from xylose to butyric acid started to decrease as the sugar concentration was above 35 g/L, while for glucose media higher glucose concentration resulted in higher yield. At low sugar concentrations (5 g/L or 15 g/L), xylose was more efficient than glucose for butyric acid generation, but at high concentrations (55 or 75 g/L), glucose was more efficient. In mixtures containing both sugars, glucose was the preferred sugar for bacteria growth and xylose was rapidly consumed only after the glucose was exhausted. The xylose to glucose ratio affected bacterial growth and butyric acid production. High xylose to glucose ratios (4:1 or 3:2) showed better butyric acid production than low ratios (1:1, 2:3, or 1:4) when the total initial sugar content in the media was kept at 30 g/L.