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Abstract Biodetoxification fungus selectively degrades toxic inhibitors generated from pretreatment of lignocellulose without consuming fermentable sugars. However, one barrier for practical application is the sustained cell viability in the consequent fermentation step to compete the fermentable sugars with fermenting strains, resulting in sugar loss and reduced target product yield. This study investigated the competitive growth property between the biodetoxification fungus Paecilomyces variotii FN89 and the L-lactic acid bacterium Pediococcus acidilactici ZY271 under varying temperature and lactic acid osmatic stress. The results show that the L-lactic acid bacterium Ped. acidilactici ZY271 showed less thermotolerance to Pae. variotii FN89 at high temperature of 45 °C to 50 °C in both synthetic medium and wheat straw hydrolysate. In the higher temperature environment, the growth of the biodetoxification strian failed to compete with the lactic acid fermentation strain and was quickly eliminated from the fermentation system. The high temperature fermentation facilitated a fast transition from the detoxification stage to the fermentation stage for higher production of L-lactic acid.

Abstract Background The efficient removal of toxic inhibitors from pretreated lignocellulose biomass is crucially important for consequent cellulosic ethanol fermentation. A. resinae ZN1 biodetoxifies all toxic inhibitors at the neutral pH of 4–6, and the neutralization of acid catalyst in the pretreated lignocellulose is required. However, aqueous alkaline solutions such as sodium hydroxide solution and calcium hydroxide slurry are used which generate several difficulties. Results In this study, a dry biodetoxification method was investigated using dry calcium carbonate (CaCO3) powder as an acid-neutralizing reagent to avoid the use of an aqueous alkaline solution. Dry biodetoxification provides a mild and stable pH without the generation of phenolic compounds. The acid pretreated and dry biodetoxified wheat straw was used as the feedstock of ethanol fermentation and the same performance with the wet biodetoxification using aqueous Ca(OH)2 slurry. The 72 g/L or 9.1% (v/v) of ethanol produced from wheat straw was very close to that of ethanol from corn starch. Conclusions Dry biodetoxification provided a practical method to simplify the process of conventional wet biodetoxification to reduce the time, cost and labor.