Butyric Acid Production from Wheat Straw Biomass by Simultaneous Saccharification and Fermentation and High-Productivity Reactors

Sustainable production of biofuels and chemicals by green fermentation routes is becoming attractive. In this paper, the production of butyric acid by fermentation of wheat straw is studied. This conversion process requires biomass milling, pretreatment, hydrolysis, fermentation, and recovery. Of these five processing steps, pretreatment, hydrolysis, fermentation, and recovery are particularly cost-intensive. In the current study we combined simultaneous saccharification and fermentation in one unit operation for the substrate of wheat straw. In the integrated process, 90 g L−1 of wheat straw was simultaneously saccharified and fermented to 20.8 g L−1 of total acetic and butyric acids, of which butyric acid is the main product. As a result of the integration of saccharification with fermentation into a single streamlined workflow, the economics of the process significantly improved. In the fermentation process in which water was recycled, 39.9 g L−1 total acid (acetic acid + butyric acids) was produced. This is comparable to 40.8 g L−1 total acid produced in the glucose-fed control fermentation. Using cell-recycling technology, acid productivity was increased by 8–10 fold (800–1000%) from wheat straw hydrolysate as a feed. In this article, product yield, productivity, and selectivity were deemed to have high potential.