초록
Mannosylerythritol lipids (MEL) are glycolipid biosurfactants, produced by Pseudozyma spp., with increasing commercial interest. While MEL can be produced from d-glucose and d-xylose, the direct conversion of the respective lignocellulosic polysaccharides, cellulose and xylan, was not reported yet. The ability of Pseudozyma antarctica PYCC 5048<SUP>T</SUP> and Pseudozyma aphidis PYCC 5535<SUP>T</SUP> to use cellulose (Avicel<SUP>®</SUP>) and xylan (beechwood) as carbon and energy source has been assessed along with their capacity of producing cellulolytic and hemicellulolytic enzymes, toward a consolidated bioprocess (CBP) for MEL production. The yeasts assessed were neither able to grow in medium containing Avicel<SUP>®</SUP> nor produce cellulolytic enzymes under the conditions tested. On contrary, both yeasts were able to efficiently grow in xylan, but MEL production was only detected in P. antarctica PYCC 5048<SUP>T</SUP> cultures. MEL titers reached 1.3g/l after 10 days in batch cultures with 40g/l xylan, and 2.0g/l in fed-batch cultures with xylan feeding (additional 40g/l) at day 4. High levels of xylanase activities were detected in xylan cultures, reaching 47-62U/ml (31-32U/mg) at 50<SUP>o</SUP>C, and still exhibiting more than 10U/ml under physiological temperature (28<SUP>o</SUP>C). Total β-xylosidase activities, displayed mainly as wall-bounded and extracellular activity, accounted for 0.154 and 0.176U/ml in P. antarctica PYCC 5048<SUP>T</SUP> and P. aphidis PYCC 5535<SUP>T</SUP> cultures, respectively. The present results demonstrate the potential of Pseudozyma spp. for using directly a fraction of lignocellulosic biomass, xylan, and combining in the same bioprocess the production of xylanolytic enzymes with MEL production.