Harnessing industrial waste for the co-production of mannosylerythritol and cellobiose lipids by Ustilago maydis

Abstract

Ustilago maydis, the fungus responsible for corn smut disease, produces valuable glycolipid biosurfactants: mannosylerythritol lipids (MELs) and cellobiose lipids (CBLs). These compounds have gained industrial interest due to their surface-active and antimicrobial properties. However, downstream processing challenges have hindered their commercial adoption, especially in the absence of hydrophobic substrates. This study explored the co-production of MELs and CBLs by U. maydis DSM 4500 using pure and waste-derived substrates. Results showed that CBLs were predominantly produced during the exponential growth phase, whereas MELs were favoured in the stationary phase. While acidic (pH 2.6) and nitrogen-limited conditions enhanced glycolipid production, microbial growth was inhibited, reducing overall yields. To overcome this, a two-stage strategy was implemented. Biomass formation was first optimized under neutral pH (6.0) and nitrogen-replete conditions. In the second stage, biomass was transferred to glycolipid-favouring conditions, leading to a 190 % and 108 % increase in MEL and CBL titres, respectively, compared to a single-stage process. Additionally, sugarcane molasses was explored as an alternative carbon source, achieving a final CBL titre of 0.43 g/L. Though relatively low, this represents the first report of CBL production from an industrial waste stream. These findings highlight the potential for sustainable co-production of MELs and CBLs from industrial waste, paving the way for future research on optimizing yields and scalability.