16-07: Large scale verification of butyric acid fermentations at the EPAB Demo Plant in Örnsköldsvik

The global chemical industry has an annual increased market demand for butyric acid. The increased application of 4 carbon oxychemicals is not only limited to direct use but often for utilization as chemical feedstocks to generate other commercially important compounds, for example the plasticizer cellulose acetate butyrate. There are also synergistic possibilities with ethanol production. One such example is the production of ethyl butyrate, a 100% biobased solvent and specialty chemical.

Microorganisms from the genus Clostridiumare the most studied in terms of butyrate fermentations owing to their comparatively high productivities and final concentrations. One of the major costs of butyric acid fermentations is the carbon/energy sources. In this respect hydrolyzates of lignocellulosic wastes from the forest- and agricultural industry are highly interesting as they are economically available and can provide fermentable sugars of which the major components are glucose, mannose, galactose, arabinose and xylose.

We have been investigating the feasibility of using dilute sulfuric acid corn-cob and spruce hydrolyzates as feed stocks for butyric acid fermentation using C. tyrobutyricumin lab-scale fermenters. Fermentation optimization, i.e. media composition and feeding profile resulted in 27 g/L butyric acid. The process was transferred from 1L scale to 3000L at the Ethanol Demo Plant in Örnsköldsvik, Sweden, using dilute sulfuric acid corn-cob hydrolyzate and a subsequent simultaneous saccharification and fermentation (SSF).

Here we present the use of cellulosic based raw materials at demo scale resulting in the production of second generation butyric acid, i.e., not using starch based raw materials.