Improving the fermentable sugar yields of wheat straw by high-temperature pre-hydrolysis with thermophilic enzymes ofMalbranchea cinnamomea

Background Enzymatic hydrolysis is a key step in the conversion of lignocellulosic polysaccharides to fermentable sugars for the production of biofuels and high-value chemicals. However, current enzyme preparations from mesophilic fungi are deficient in their thermostability and biomass-hydrolyzing efficiency at high temperatures. Thermophilic fungi represent promising sources of thermostable and highly active enzymes for improving the biomass-to-sugar conversion process. Here we present a comprehensive study on the lignocellulosic biomass-degrading ability and enzyme system of thermophilic fungusMalbranchea cinnamomeaN12 and the application of its enzymes in the synergistic hydrolysis of lignocellulosic biomass. Results Malbranchea cinnamomeaN12 was capable of utilizing untreated wheat straw to produce high levels of xylanases and efficiently degrading lignocellulose under thermophilic conditions. Temporal analysis of the wheat straw-induced secretome revealed thatM. cinnamomeaN12 successively degraded the lignocellulosic polysaccharides through sequential secretion of enzymes targeting xylan and cellulose. Xylanase-enriched cocktail fromM. cinnamomeaN12 was more active on native and alkali-pretreated wheat straw than the commercial xylanases fromTrichoderma reeseiover temperatures ranging from 40 to 75 degrees C. Integration ofM. cinnamomeaN12 enzymes with the commercial cellulase preparation increased the glucose and xylose yields of alkali-pretreated wheat straw by 32 and 166%, respectively, with pronounced effects at elevated temperature. Conclusions This study demonstrated the remarkable xylanase-producing ability and strategy of sequential lignocellulose breakdown ofM. cinnamomeaN12. A new process for the hydrolysis of lignocellulosic biomass was proposed, comprising thermophilic enzymolysis by enzymes ofM. cinnamomeaN12 followed with mesophilic enzymolysis by commercial cellulases. DevelopingM. cinnamomeaN12 as platforms for thermophilic enzyme mixture production will provide new perspectives for improved conversion yields for current biomass saccharification schemes.