Kinetic limitations in xylan conversion to caproate

Abstract

The aim of this work is to identify the kinetic bottleneck during xylan fermentation targeting caproic acid production by shortening the hydraulic retention time (HRT) in a continuous reactor. The highest caproic acid yield (0.09 Cmol/Cmol-s) was achieved at an HRT of 4 d, suggesting that chain elongation process is optimised at these conditions. At shorter HRT (2 and 1 day), caproic acid yield decreased in favour of butyric acid, but xylan was always fully converted. The latter indicates that xylan conversion rate is faster that the chain elongation process, and therefore, the bottleneck of caproate production from xylan fermentation is the chain elongation step.