Lipid Production for Microbial Biodiesel by the Oleagenious Yeast Rhodotorula glutinis Using Hydrolysates of Wheat Straw and Miscanthus as Carbon Sources

Abstract

This study investigated the lipid production potential of the red-yeast Rhodotorula glutinis grown on non-detoxified hydrolysates from wheat straw and Miscanthus. The experiments were carried out as batch fermentation experiments in a five liter fermenter. Generally, wheat straw was found to provide a higher sugar content (24.2 g L−1) compared to Miscanthus (20.7 g L−1) which resulted in a higher lipid production. When wheat straw hydrolysate was used as a carbon source, cell mass and lipid production showed a significant increase in maximum cell mass and lipid yield of 11.8 and 1.4 g L−1, respectively. Maximum cell mass growth of R. glutinis on Miscanthus hydrolysate as a carbon source fell within the same range (11.8 g L−1), whereas maximum lipid production after 96 h was lower (0.93 g L−1). A major limitation for cell growth and lipid production was the rapid exhaustion of the total sugar content after 96 h of fermentation in both hydrolysates. This resulted in a decelerated cell growth and lipid production. Lipids from both hydrolysates were dominated by long chain fatty acids, in particular C 16:0, C 18:1 and C 18:2. This composition of lipids corresponds to the common fatty acid obtained from oleaginous microorganisms and indicates a good level of suitability for biodiesel production.