P34: Submerged lignocellulose fermentations at high dry matter concentrations

Monday, November 7, 2011
Capri Ballroom (Marriott Marco Island)
Johan van Groenestijn, Earth, Environmental and Life Sciences, TNO, Zeist, Netherlands and Peter J. Punt, Microbiology & Systems Biology, TNO, Zeist, Netherlands

Companies are interested to shift from sucrose and starch to lignocellulosic biomass as feedstock for fermentation processes. Two challenges are (1) the application of high concentrations of substrate and product, which is important for the economy of fermentation, and (2) production of toxic by-products in lignocellulose pretreatment. Recently TNO developed a pretreatment method in which biomass is heated using superheated steam under acidic conditions at 30-60 % w/w/ dry matter without producing much inhibitors. The process is followed by fed-batch preliquefaction with hydrolytic enzymes, and subsequent simultaneous saccharification and fermentation with hydrolytic enzymes and microorganisms. This way an anaerobic SSF with Saccharomyces cerevisiae could be carried out at a concentration of 38% (w/w) wheat straw dry matter. In this way, 51 g ethanol L-1 was produced. More accessible cellulose was still available for production of yet more ethanol, but the ethanol production was limited by the reversible inactivation of the enzymes and irreversible inactivation of the yeast by high concentrations of toxic compounds in the straw hydrolysate. The production method developed yielded low amounts of by-products, such as furfural, 5-hydroxymethyl furfural, levulinic acid, and lactic acid. Similar SSF were carried out using Pseudomonas putida and Aspergillus niger to demonstrate that submerged aerobic fermentations can be carried out as well using 30% dry matter wheat straw as a substrate in conventional fermenters.

See more of: Poster Session
See more of: Invited Oral Papers