Yeast fermentation of carboxylic acids obtained from pyrolytic aqueous phases for lipid production Jieni Lian a , Manuel Garcia-Perez a , Ralph Coates b , Hongwei Wu c , Shulin Chen a,⇑ a Biological Systems Engineering, Washington State University, WA 99164-6120, USA b Amaron Energy, Salt Lake City, UT 84103, USA c Fuels and Energy Tech. Institute, Curtin University, Box U1987, Perth WA 6845, Australia highlights " A fractional condenser was used to separate pyrolytic aqueous phase and bio-oil. " Model compounds representing C1–C4 pyrolytic molecules were fermented. " The optimal acetate concentration for fermentation with C. curvatus was determined. " A technology to produce lipid from the pyrolytic aqueous phase was proposed. graphical abstract article info Article history: Received 5 March 2012 Received in revised form 1 May 2012 Accepted 3 May 2012 Available online 18 May 2012 Keywords: Acetate Formate Yeast Lipid fermentation Pyroligneous water abstract The presence of very reactive C1–C4 molecules adversely affects the quality bio-oils produced from the pyrolysis of lignocellulosic materials. In this paper a scheme to produce lipids with Cryptococcus curvatus from the carboxylic acids in the pyrolytic aqueous phase collected in fractional condensers is proposed. The capacities of three oleaginous yeasts C. curvatus, Rhodotorula glutinis, Lipomyces starkeyi to ferment acetate, formate, hydroxylacat-aldehyde, phenol and acetol were investigated. While acetate could be a good carbon source for lipid production, formate provides additional energy and contributes to yeast growth and lipid production as auxiliary energy resource. Acetol could slightly support yeast growth, but it inhibits lipid accumulation. Hydroxyacetaldehyde and phenols showed high yeast growth and lipid accumulation inhibition. A pyrolytic aqueous phase with 20 g/L acetate was fermented with C. curvatus, after neutralization and detoxification to produce 6.9 g/L dry biomass and 2.2 g/L lipid. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The ever growing demand for goods and services and global warming require new approaches to produce higher quantities of fuels and chemicals which are currently produced mostly from non renewable sources (Doma, 2011). As a natural, abundant and renewable resource, biomass is being considered as the only option for the production of renewable C-based fuels and chemicals to mit- igate the potential detrimental effects of a gradual depletion of petroleum resources. Pyrolysis oil, a product of biomass simulta- neous depolymerization and fragmentation at temperatures be- tween 300 and 600 °C is being studied as a promising platform for fuels and chemicals production (Jarboe et al., 2011; Garcia-Perez et al., 2007, 2008). However, the complex composition of these oils, with more than 400 chemicals identified, makes their refining difficult. The pres- ence of carboxylic acids is particularly troublesome (Garcia-Perez et al., 2010). These compounds cause phase separation, reduce 0960-8524/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2012.05.010 ⇑ Corresponding author. Address: Biological Systems Engineering Department, Washington State University, Pullman, WA 99164-6120, USA. E-mail address: chens@wsu.edu (S. Chen). Bioresource Technology 118 (2012) 177–186 Contents lists available at SciVerse ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech