2-12: One-step production of fumarate from pretreated corn stover by using recombinant cellulolytic Bacillus subtilis

Fumaric acid (or fumarate, an equivalent compound) was identified to be among the top 12 building block chemicals by the U.S. DOE in 2004. Currently, fumaric acid is produced chemically from maleic anhydride, which in turn is produced from butane – a key product made from crude oil. Its production relies heavily on crude oil, generates air pollution, and produces greenhouse gases. The adverse effects of high crude oil prices, climate change concerns, and threats to energy security caused by fumaric acid production may be mitigated through the use of an alternative method: fermentation from renewable sugars. Consolidated bioprocessing (CBP) is a low-cost cellulosic biomass processing by integrating cellulase production, cellulose hydrolysis, and sugar fermentation into a single step. Unlike Gram-positive Clostridium spp., Gram-negative Escherichia coli, or yeast, Bacillus subtilis has many unbeatable advantages for industrial biocommodities production as the potential CBP microorganism. A most recent study demonstrated that the recombinant Bacillus subtilis with surface-displayed minicellulosome can grow on untreated plant biomass. In this work, we successfully converted B. subtilis to become a fumarate producer. We further introduced two heterologous pathways into the recombinant microorganism, increasing fumarate yield about 10-fold. In order to make fumarate the major fermentation product, we systematically optimized the fermentation conditions to achieve the one-step production of fumarate from pretreated lignocellulosic biomass (corn stover), with fumarate as the dominant fermentation product. The production of renewable building block chemicals such as fumaric acid from cellulosic materials would be a key component of a future sustainable biomanufacturing industry.