|LIN, HUI - University Of California
|HILDEBRAND, AMANDA - University Of California
|ZHILIANG, FAN - University Of California
Submitted to: Enzyme and Microbial Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2016
Publication Date: 1/6/2017
Citation: Lin, H., Hildebrand, A., Kasuga, T., Zhiliang, F. 2017. Engineering Neurospora crassa for cellobionate production directly from cellulose without any enzyme addition. Enzyme and Microbial Technology. 99:25-31. doi: 10.1016/j.enzmictec.2016.12.009.
Interpretive Summary: Both plant pathogenic fungi and oomycetes produce cellulases to degrade plant cell wall materials. Cellobiose, the main product of cellulases will then be converted to cellobionate by the action of cellobiose dehydrogenase. We found that the exogenous addition of laccase and redox mediator to the culture was able to improve the yield of cellobionate from cellulose. This is the first report of conversion of cellulose to a sugar-like chemical without any enzyme addition.
Technical Abstract: A previously engineered strain of N. crassa F5'ace-1'cre-1'ndvB) with six out of seven ß-glucosidase (bgl) genes, two transcription factors (cre1 and ace-1) and cellobionate phosphorylase (ndvB) deleted was able to produce cellobiose and cellobionate directly from cellulose without the addition of exogenous enzymes. The exogenous addition of laccase and redox mediator to the culture was found to be able to improve the yield of cellobionate from cellulose. In this study, the F5'ace-1'cre-1'ndvB strain was engineered to produce laccase heterologously. Laccase from two different sources were expressed under three different promoters.The laccase expression by different recombinant strains was characterized. The strain express laccase from Botrytis aclada produced the highest activity. Using this strain, cellulose was converted to cellobionate without any enzyme addition. The yield of cellobionate from hydrolyzed cellulose was about 90%. This is the first report of conversion of cellulose to a sugar-like chemical without any enzyme addition.