ARS | Publication request: Biological Abatement of Fermentation Inhibitors for Ethanol Production from Bioenergy Crops

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 27, 2010
Publication Date: N/A

Technical Abstract: Agricultural residues and energy crops are potential feedstocks for conversion to fuels and chemicals. However, lignocellulose is recalcitrant to biochemical conversion and requires extensive upfront processing. Dilute-acid pretreatment of biomass has been shown to be highly effective for extracting hemicellulose associated sugars and increasing the reactivity of cellulose to cellulase enzymes. The physical and/or chemical pretreatment conditions are necessarily harsh in order to deconstruct the plant cell wall, and as a result also generate side-products that are inhibitory to fermentation. These include furan aldehydes, phenolic compounds, and aromatic and aliphatic aldehydes and acids typically present in hydrolysed biomass. The inhibitory compounds prevent efficient conversion of lignocellulosic hydrolysates, because these various inhibitors retard microbial growth and decrease product productivity and yield. Because inhibitors from lignocellulose disrupt the biomass conversion process, the inhibitory compounds must be mitigated prior to fermentation. Inhibitors can be abated prior to fermentation through processes such as dilution, adsorption, extraction, and precipitation. Drawbacks to these methods, however, include costs and in some cases additional waste generation. We have developed an alternate method for eliminating inhibitors that relies on biological abatement, in which inhibitors are removed via microbial metabolism of undesirable compounds. This method has specific advantages compared to alternate methods including suitability for treating liquid-solid mixtures, minimal generation of waste streams, no need for chemical inputs, and no requirement for recharging, as required for example by adsorption resins. The cornerstone of the process is finding an effective microorganism that has the ability to efficiently metabolize the targeted chemicals and is itself able to tolerate the presence of these toxic compounds. Previously, Coniochaeta ligniaria NRRL30616 was discovered using a natural screen and shown to efficiently detoxify corn stover dilute acid hydrolysates prior to fermentation. Here, this initial work is expanded to include three additional biomass feedstocks, which include warm and cool season grasses and a legume.