Cuttlebone is a highly organized calcium carbonate biomineral with an elaborate macroporous architecture consisting of mineralized sheets and supporting wall structures that are constructed on a β-chitin matrix (figure). Removal of the calcium carbonate by demineralization results in an intact polysaccharide matrix that has been remineralized in the presence of alkaline silicate solutions to produce ordered macroporous β-chitin−silica replicas of the cuttlebone architecture. By control of the supersaturation and extent of deacetylation of the organic matrix, high-fidelity biomimetic facsimiles of the 3-D interconnected organic framework can be obtained by facile processing at room temperature.
To develop a Trichoderma reesei strain appropriate for the saccharification of pretreated cellulosic biomass, a recombinant T. reesei strain, X3AB1, was constructed that expressed an Aspergillus aculeatus β-glucosidase 1 with high specific activity under the control of the xyn3 promoter. The culture supernatant from T. reesei X3AB1 grown on 1% Avicel as a carbon source had 63- and 25-fold higher β-glucosidase activity against cellobiose compared to that of the parent strain PC-3-7 and that of the T. reesei recombinant strain expressing an endogenous β-glucosidase I, respectively. Further, the xylanase activity was 30% lower than that of PC-3-7 due to the absence of xyn3. X3AB1 grown on 1% Avicel-0.5% xylan medium produced 2.3- and 3.3-fold more xylanase and β-xylosidase, respectively, than X3AB1 grown on 1% Avicel. The supernatant from X3AB1 grown on Avicel and xylan saccharified NaOH-pretreated rice straw efficiently at a low enzyme dose, indicating that the strain has good potential for use in cellulosic biomass conversion processes.
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