Lipid production by Rhodosporidium toruloides growing on media presenting composition similarities with the spent sulfite liquor in batch and fed-batch cultures

Aim of this study is to explore the effect of sodium lignosulfonate (SL), a paper industry by-product, on cell growth and lipid production by the yeast Rhodosporidium toruloides, cultivated on xylose-based media, that mimic the principal waste-stream originated from paper production facilities (viz. the spent-sulfite liquor). Yeast lipids present increasing interest as alternative non-food feedstocks for biodiesel production. Strains DSM 444 and NRRL Y-27012 were shake-flask cultured under nitrogen-limiting conditions using xylose at 50 g/L, and SL was added at varying concentrations. Finally, a fed-batch bioreactor trial of the strain NRRL Y-27012 with optimum SL addition was carried out. In the strain DSM 4444, maximum lipid production was obtained in media supplemented with 20 g/L SL, where lipid of 4.77 g/L occurred. In NRRL Y-27012 strain, maximum lipid production was seen with the addition of 10 g/L SL (lipid =5.30 g/L). In fed-batch bioreactor experiments carried out with the strain NRRL Y-27012, lipid =17.0 g/L (corresponding dry biomass =29.7 g/L) was achieved. The yield of lipid produced per unit of xylose consumed was 0.19 g/g. Lipids containing increased concentrations of oleic acid, constituting thus perfect materials amenable to be converted into “2nd generation” biodiesel were synthesized.