Lipid products from agriculture by-products and pyrolytic oil

Abstract

Bio-oil derived from fast pyrolysis of lignocellulosic biomass contains various substrates that can be fermented by microorganisms to produce various fuels and chemicals. The aim of the present work was to utilize the acetic acid-rich fraction of bio-oil for growth and lipid production in the microalga Chlamydomonas reinhardtii. The acetic acid-rich fraction of bio-oil derived from fast pyrolysis of softwood contains around 26% (w/w) of acetic acid, formic acid, methanol, furfural, acetol, and various phenolics as identified compounds, and 13% (w/w) of unidentified compounds. Among those identified compounds, phenolics were most inhibitory to algal growth, followed by acetol. To enhance the fermentability of the acetic acid-rich bio-oil fraction by microalgae, activated carbon treatment was used to reduce the toxicity of this bio-oil fraction, while metabolic evolution was used to enhance the toxicity tolerance of the microalgae strain. Combining the activated carbon treatment and using adapted algal strain through metabolic evolution resulted in significant improvement of algal growth performance on acetic acid-rich bio-oil fraction; the algae were capable of growing in medium with 100% of acetic acid being replaced by bio-oil fraction. The biomass derived from different treatments exhibited similar fatty acid profiles, 28 with slightly decreasing total fatty acid content. The fast pyrolysis-fermentation process is a viable approach for producing fuels and chemicals from lignocellulosic biomass.