초록
<P><B>Background</B></P><P>Butyric acid is an important chemical currently produced from petrochemical feedstocks. Its production from renewable, low-cost biomass in fermentation has attracted large attention in recent years. In this study, the feasibility of corn husk, an abundant agricultural residue, for butyric acid production by using <I>Clostridium tyrobutyricum</I> immobilized in a fibrous bed bioreactor (FBB) was evaluated.</P><P><B>Results</B></P><P>Hydrolysis of corn husk (10% solid loading) with 0.4 M H<SUB>2</SUB>SO<SUB>4</SUB> at 110 °C for 6 h resulted in a hydrolysate containing ~ 50 g/L total reducing sugars (glucose:xylose = 1.3:1.0). The hydrolysate was used for butyric acid fermentation by <I>C. tyrobutyricum</I> in a FBB, which gave 42.6 and 53.0% higher butyric acid production from glucose and xylose, respectively, compared to free-cell fermentations. Fermentation with glucose and xylose mixture (1:1) produced 50.37 ± 0.04 g L<SUP>−1</SUP> butyric acid with a yield of 0.38 ± 0.02 g g<SUP>−1</SUP> and productivity of 0.34 ± 0.03 g L<SUP>−1</SUP> h<SUP>−1</SUP>. Batch fermentation with corn husk hydrolysate produced 21.80 g L<SUP>−1</SUP> butyric acid with a yield of 0.39 g g<SUP>−1</SUP>, comparable to those from glucose. Repeated-batch fermentations consistently produced 20.75 ± 0.65 g L<SUP>−1</SUP> butyric acid with an average yield of 0.39 ± 0.02 g g<SUP>−1</SUP> in three consecutive batches. An extractive fermentation process can be used to produce, separate, and concentrate butyric acid to > 30% (w/v) sodium butyrate at an economically attractive cost for application as an animal feed supplement.</P><P><B>Conclusion</B></P><P>A high concentration of total reducing sugars at ~ 50% (w/w) yield was obtained from corn husk after acid hydrolysis. Stable butyric acid production from corn husk hydrolysate was achieved in repeated-batch fermentation with <I>C. tyrobutyricum</I> immobilized in a FBB, demonstrating that corn husk can be used as an economical substrate for butyric acid production.</P>