Encapsulation-Induced Stress Helps <em>Saccharomyces cerevisiae </em>Resist Convertible Lignocellulose Derived Inhibitors

• Main Authors: Johan O. Westman, Ramesh Babu Manikondu, Carl Johan Franzén, Mohammad J. Taherzadeh
• Format: Article
• Language: English
• Published: MDPI AG 2012-09-01
• Series: International Journal of Molecular Sciences
• Subjects: lignocellulosic hydrolysate; ethanol; furfural; HMF (5-hydroxymethyl furfural); carboxylic acids; encapsulation; <em>Saccharomyces cerevisiae</em> biofuel; inhibitors; q-PCR
• Online Access: http://www.mdpi.com/1422-0067/13/9/11881

The ability of macroencapsulated <em>Saccharomyces cerevisiae </em>CBS8066<em> </em>to withstand readily and not readily <em>in situ</em> convertible lignocellulose-derived inhibitors was investigated in anaerobic batch cultivations. It was shown that encapsulation increased the tolerance against readily convertible furan aldehyde inhibitors and to dilute acid spruce hydrolysate, but not to organic acid inhibitors that cannot be metabolized anaerobically. Gene expression analysis showed that the protective effect arising from the encapsulation is evident also on the transcriptome level, as the expression of the stress-related genes <em>YAP1</em>, <em>ATR1</em> and <em>FLR1</em> was induced upon encapsulation. The transcript levels were increased due to encapsulation already in the medium without added inhibitors, indicating that the cells sensed low stress level arising from the encapsulation itself. We present a model, where the stress response is induced by nutrient limitation, that this helps the cells to cope with the increased stress added by a toxic medium, and that superficial cells in the capsules degrade convertible inhibitors, alleviating the inhibition for the cells deeper in the capsule.