Biomass pretreatment affects Ustilago maydis in producing itaconic acid

Abstract

BackgroundIn 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.ResultsU. 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.ConclusionThe 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.

Nitrogen Source Affects Glycolipid Production and Lipid Accumulation in the Phytopathogen Fungus <i>Ustilago maydis</i>

“…Cytosolic ATP-Citrate lyase is necessary to recover the Acetyl CoA in the cytosol for use in lipid synthesis, and U. maydis must use this route due to the presence of an ATP-Citrate lyase gene (UM 01005.1) [26] [27]. During the production of itaconic acid (methylene succinic acid) in U. mayids during nitrogen-limited conditions, it has been suggested that the relative oxygen content decreased, making the biomass more reduced and allowing for the accumulation of less oxygenated compounds as hydrocabons [28]. These authors also included in their study the influence of nitrogen supply and found that nitrogen limitation increased the cell size, probably due to the accumulation of lipids.…”

Activating Intrinsic Carbohydrate-Active Enzymes of the Smut Fungus Ustilago maydis for the Degradation of Plant Cell Wall Components

“…Numerous molecular tools have been developed over the last few years, including resistance markers, protein tags (39), and efficient strain generation by Golden Gate cloning (40). In addition, in bioreactors, the fungus confers a remarkably high resistance to shearing forces and to impurities in the fermentation broth, like those observed after biomass pretreatment (26,41). The largescale cultivation in bioreactors is well established, for instance, for the closely related fungus Pseudozyma tsukubaensis (42).…”

Effect of Lignocellulose Related Compounds on Microalgae Growth and Product Biosynthesis: A Review

“…Xylitol, a sweetener, was produced from xylose by Candida guilliermondii [17], while Saccharomyces cerevisae [54] and Clostridium beijerinckii [55] convert sugars to ethanol and butanol, respectively-second generation biofuels. Itaconic acid, a building block for fibers and rubbers, was produced by Ustilago maydis from xylose or glucose [18] and hydrogen, a third generation biofuel, is obtained from sugars with the use of Caldicellulosiruptor saccharolyticus [16]. However, the presence of three major polymers and other minor substances in lignocellulose, their rigidity and strong structure make the access to valuable carbohydrates very complicated.…”

“…The ability of microalgae to grow on organic substrates raises the possibility of cultivating microalgae on lignocellulose feedstock and thus reduce cultivation costs and increase productivity. Lignocellulose is the world's most abundantly available raw plant material that can become a promising feedstock for microorganisms such as bacteria, yeasts and fungi to produce high value added products and biofuels [16][17][18]. Energies 2014, 7…”

“…Hot water extraction [57] and dilute acid treatment [58,64,65] are implemented to release sugars and organic acids localized in the hemicellulose structure. Xylans in hemicellulose can also be selectively extracted by organic solvents [18] such as oxalic acid combined with methyltetrahydrofuran (2-MTHF) or hydrolyzed enzymatically by xylanases into oligomers and simple sugars [66]. Alkaline treatment with NaOH or Ca(OH) 2 [16] and Na 2 CO 3 [59] breaks linkages in the lignin structure and removes phenolic compounds.…”