New-to-nature sophorose analog: a potent inducer for gene expression in Trichoderma reesei

• Novel sophorose ester of previously unknown structure is described.
• This sophorose ester is shown to be a potent inducer of the cellulase gene in Trichoderma.
• The inducer is very slowly metabolized by the host, allowing it to be added only once.
• A method of preparing the inducer from lactone-form sophorolipid is described.

Controlled hydrolysis of lactonic sophorolipids from Starmerella bombicola yields a previously undescribed sophorose analog that potently induces cellulase in Trichoderma reesei Rut-C30. Acid treatment of natural sophorolipids results in a mixture of monoacetylated, deacetylated, and diacetylated sophorolipids in acidic and lactonic forms. Isolation of the active components of the mixture, followed by structure determination by MS and NMR, reveals a new chemical entity, in which the lactone ring has been opened at the C-1′ rather than at the C-4″ position of the sophorose moiety. This sophorose ester is resistant to degradation by the host and is at least 28 times more powerful an inducer than sophorose in shake-flask culture. Even at low concentrations (0.05 mM), the chemically modified sophorolipid effectively induces cellulase. With further improvements, this highly enabling technology can potentially reduce the cost of enzymes produced in T. reesei and can facilitate the rapid deployment of enzyme plants to support the nascent cellulosic biofuels and biochemicals industries.