Fermentation of bioenergy crops into ethanol using biological abatement for removal of inhibitors

Abstract

Biological abatement was used to condition dilute acid-pretreated hydrolysates of three perennial herbaceous crops that are potential bioenergy feedstocks: switchgrass, reed canarygrass, and alfalfa stems. Fungal isolate Coniochaeta ligniaria was inoculated into the hydrolysates to metabolize and remove inhibitory compounds prior to yeast fermentation of glucose. Switchgrass, reed canarygrass, and alfalfa stem samples were pretreated with dilute acid at 10% w/w biomass loading and subjected to bioabatement with strain NRRL30616, to prepare the material for simultaneous saccharification of cellulose and fermentation by Saccharomyces cerevisiae. Bioabatement eliminated the extended fermentation lag times associated with inhibitory compounds and observed for the unconditioned biomass hydrolysates controls. Bioabatement was as effective as lime conditioning at reducing fermentation lag times. Prolonged incubations with the bioabatement microbe resulted in consumption of some glucose and reduced production of ethanol.