A dose dependent response of yeast to HMF was demonstrated and a lag phase was http://www.selleckchem.com/products/dorsomorphin-2hcl.html used to measure levels of strain tol erance. The yeast Saccharomyces cerevisiae is able to in situ detoxify HMF into the less toxic com pound FDM through NADPH dependent reductions. Typically, yeast strains show a lag of delayed cell growth after inhibitor challenge such as with fur fural and HMF, under sublethal doses. Once HMF and furfural inhibitor levels were chemically reduced to a certain lower concentration, cell growth recovered and the glucose to ethanol conversion accelerated at a faster rate than would normally occur. It was suggested that genomic adaptation occurred during the lag phase. In fact, inhibitor tolerant yeast strains showed significant shorter lag phases under the inhibitor chal lenges compared with a wild type strain.

Gene expressions of selected pathways of the tolerant yeast are distinct from the wild type control. Sequence mutations are common and a large number of single nucleotide polymorphism mutations were observed throughout all 16 chromosomes for a tolerant yeast strain. Adaptations appear to occur at the genome level. However, little is known about gene expression response and regulatory events for yeast dur ing the adaptation lag phase. The objective of this study was to characterize transcriptome response of yeast dur ing the lag phase after the HMF challenge. Using a com parative time course study, we investigated the dynamics of transcriptome profiling during this critical stage applying DNA microarray assays and regulatory analysis.

Important genes, together with transcription factors involved in the HMF stress response, were identi fied. The functions of selective candidate genes were verified by corresponding gene deletion mutation strains. Significant regulatory interaction networks were uncovered during the genome adaptation in yeast. Results of this study provide insight into mechanisms of yeast adaptation and tolerance to lignocellulose derived inhibitors. This will directly aid engineering efforts for more tolerant strain development. Results Cell growth response and metabolic conversion profiles Compared to a non treated control, yeast challenged by HMF displayed a significant drop in cell growth as mea sured by OD600 absorbance 2 h after the treatment.

Although the cell growth was recovered at a later time, cell density of the HMF treated yeast was relatively low throughout the course of the study. Simi larly, glucose consumption for the HMF treated culture was slower and glucose was depleted at 16 h, approxi mately 4 h later than the non treated control. As AV-951 expected, HMF was undetectable and FDM was detected as HMF conversion product in HMF treated cultures less than 24 h after incubation. No HMF or FDM was detected from the control culture.