BACKGROUND: In the last years, the biotechnological production of platform 
chemicals for fuel components has become a major focus of interest. Although 
ligno-cellulosic material is considered as suitable feedstock, the almost 
inevitable pretreatment of this recalcitrant material may interfere with the 
subsequent fermentation steps. In this study, the fungus Ustilago maydis was 
used to produce itaconic acid as platform chemical for the synthesis of 
potential biofuels such as 3-methyltetrahydrofuran. No studies, however, have 
investigated how pretreatment of ligno-cellulosic biomass precisely influences 
the subsequent fermentation by U. maydis. Thus, this current study aims to first 
characterize U. maydis in shake flasks and then to evaluate the influence of 
three exemplary pretreatment methods on the cultivation and itaconic acid 
production of this fungus. Cellulose enzymatically hydrolysed in seawater and 
salt-assisted organic-acid catalysed cellulose were investigated as substrates. 
Lastly, hydrolysed hemicellulose from fractionated beech wood was applied as 
substrate.
RESULTS: U. maydis was characterized on shake flask level regarding its itaconic 
acid production on glucose. Nitrogen limitation was shown to be a crucial 
condition for the production of itaconic acid. For itaconic acid concentrations 
above 25 g/L, a significant product inhibition was observed. Performing 
experiments that simulated influences of possible pretreatment methods, U. 
maydis was only slightly affected by high osmolarities up to 3.5 osmol/L as well 
as of 0.1 M oxalic acid. The production of itaconic acid was achieved on 
pretreated cellulose in seawater and on the hydrolysed hemicellulosic fraction 
of pretreated beech wood.
CONCLUSION: The fungus U. maydis is a promising producer of itaconic acid, since 
it grows as single cells (yeast-like) in submerged cultivations and it is 
extremely robust in high osmotic media and real seawater. Moreover, U. maydis 
can grow on the hemicellulosic fraction of pretreated beech wood. Thereby, this 
fungus combines important advantages of yeasts and filamentous fungi. 
Nevertheless, the biomass pretreatment does indeed affect the subsequent 
itaconic acid production. Although U. maydis is insusceptible to most possible 
impurities from pretreatment, high amounts of salts or residues of organic acids 
can slow microbial growth and decrease the production. Consequently, the 
pretreatment step needs to fit the prerequisites defined by the actual 
microorganisms applied for fermentation.