Butyric acid fermentation from pretreated and hydrolysed wheat straw by an adapted C lostridium tyrobutyricum strain

Butyric acid is a valuable building‐block for the production of chemicals and materials and nowadays it is produced exclusively from petroleum. The aim of this study was to develop a suitable and robust strain of C lostridium tyrobutyricum that produces butyric acid at a high yield and selectivity from lignocellulosic biomasses. Pretreated (by wet explosion) and enzymatically hydrolysed wheat straw ( PHWS ), rich in C6 and C5 sugars (71.6 and 55.4 g l −1 of glucose and xylose respectively), was used as substrate. After one year of serial selections, an adapted strain of C . tyrobutyricum was developed. The adapted strain was able to grow in 80% (v v −1 ) PHWS without addition of yeast extract compared with an initial tolerance to less than 10% PHWS and was able to ferment both glucose and xylose. It is noticeable that the adapted C . tyrobutyricum strain was characterized by a high yield and selectivity to butyric acid. Specifically, the butyric acid yield at 60–80% PHWS lie between 0.37 and 0.46 g g −1 of sugar, while the selectivity for butyric acid was as high as 0.9–1.0 g g −1 of acid. Moreover, the strain exhibited a robust response in regards to growth and product profile at pH 6 and 7.