Lipid production from hemicellulose with Lipomyces starkeyi in a pH regulated fed batch cultivation

This study investigated lipid production from the hemicellulosic fraction of birch wood by the oleaginous yeast Lipomyces starkeyi. Birch wood chips were thermochemically pretreated by hot water extraction, and the liquid phase, containing 45.1 g/l xylose as the major sugar, 13.1 g/l acetic acid and 4.7 g/l furfural was used for cultivations of L. starkeyi CBS1807. The hydrolysate strongly inhibited yeast growth; the strain could only grow in medium containing 30% of hydrolysate, at pH 6. At pH 5, growth stopped already upon addition of about 10% hydrolysate. In fed‐batch cultures fed with hydrolysate or a model xylose/ acetic acid mixture, co‐consumption of xylose and acetic acid was observed, which resulted in a pH‐increase. This phenomenon was utilised to establish a pH‐stat fed batch cultivation, where, after an initial feeding hydrolysate or model mixture was connected to the pH‐regulation system of the bioreactor. Under those conditions we obtained growth and lipid production in cultures grown on either xylose or glucose during the batch phase. In cultivations fed with model mixture, a maximum lipid content of 60.5% of the cell dry weight (CDW) was obtained; however, not all xylose was consumed. When feeding hydrolysate, growth was promoted and carbon sources were completely consumed, resulting in higher CDW with maximum lipid content of 51.3%. In both cultures the lipid concentration was 8 g/l and a lipid yield 0.1 g/ g carbon source was obtaine...
Source: Yeast - Category: Molecular Biology Authors: Tags: ISSY32 Special Issue Source Type: research