Acetate-detoxification of wood hydrolysates with alkali tolerant Bacillus sp. as a strategy to enhance the lipid production from Rhodosporidium toruloides

The aim of the current work was to convert an acetate-rich hemicellulose liquid fraction (LF) from hot-water extraction of Betula pendula to oils for biodiesel, with Rhodosporidium toruloides. The toxicity of acetate was circumvented by biological detoxification with an isolated alkali-tolerant and acetate-resistant Bacillus sp. strain. Removal of other lignocellulose-derived inhibitors, such as furfural and phenols, was evaluated by two strategies; an activated carbon (AC) treatment of the undiluted LF, and dilution of the LF by 25% (0.75LF) and 50%. (0.50LF). The bacterium consumed most of the acetic acid in 6-8 days in the treated or diluted media, which were subsequently used for cultivation of the yeast, for conversion of sugars to oils. The oil concentration reached 2.8 and 1.8 g/L, in the AC LF and 0.75LF medium, respectively. In comparison, the oil accumulation in the same media without prior cultivation of Bacillus sp. was 0.86 and 0.03 g/L, respectively.