Enhanced production of butyric acid through immobilization of Clostridium tyrobutyricum in a novel inner disc-shaped matrix bioreactor

Abstract

Cell immobilization coupled with the fermentation process and subsequent separation procedure has a great potential to improve the tolerance and efficiency of microorganisms, simplify the production process, and reduce production cost. A novel inner disc-shaped matrix (IDSM), composed of a stainless steel wire mesh and covered with fabric in a disc-shaped configuration, has been developed for butyric acid production by Clostridium tyrobutyricum. Our systematic investigation of the effects of fibrous materials, matrix size, and quantity on cell loading and butyric acid production resulted in a system, namely, fed-batch mode in an IDSMB, which achieved a high butyric acid concentration of 61.87 g/L, a productivity of 0.72 g/L·h productivity, and a yield of 0.42 g/g. The system was also evaluated for its long-term performance in a repeated-batch mode for 10 cycles. The highest concentration of butyric acid reached in 1 cycle was approximately 25.5 g/L, and the butyric yield varied from 0.41 to 0.47 g/g, with an average yield of 0.44 g/g per cycle. The volumetric productivity of butyric acid varied from 0.91 to 1.31 g/L·h, with an average of 1.16 g/L·h. The IDSMB system developed in this work for butyric acid production could be extremely applicable for industrial applications in organic acid biosynthesis.