**Author details**

the industrial production of xylanases at low costs [35]. *Pichia pastoris* has also emerged as an excellent host for the commercial production of xylanases due to very high expression under its own promoters [35]. However, the success of this methylotrophic yeast, similar to *Hansenula polymorpha*, is reached with the promoters of alcohol oxidase, an enzyme involved in the methanol-utilization pathway [23]. Therefore, these promoters have limited use at the large

266 Sustainable Degradation of Lignocellulosic Biomass - Techniques, Applications and Commercialization

Filamentous fungi are capable producers of xylanases, via both heterologous and homologous gene expression, and reach high expression yields with their own promoters [35]. Filamentous fungi have already undergone intricate strain improvement for high-level protein secretion and are feasible when using the native xylanase-expressing machinery for functional expres‐ sion of foreign xylanases from remote sources. The xylanase gene from *P. griseofulvum* has been

Xylan, the major hemicellulose component, requires the synergistic action of several hemicel‐ lulase enzymes for its complete hydrolysis to monomer sugars. The principle enzyme in this processes is endo-1,4-β-xylanase, which cleaves the glycosidic bonds between xylosides, generating short xylooligosaccharides. The majority of the studied xylanases have been classified into the GH10 or GH11 families, whereas studies of the xylanases in families 5, 7, 8

The conversion of xylan to useful products represents part of our efforts to strengthen the overall economics of the processing of lignocellulosic biomass and to develop new means of energy production from renewable resources. Among these products are xyla‐ nases, enzymes that have a wide range of important industrial applications. Therefore, in the future, new methods will be developed for easier and cheaper production of these enzymes to fulfill the demands of various industries. In this context, the use of lignocel‐ lulosic agricultural waste for the production of these enzymes by either submerged or solid-sate fermentation has been very attractive, in addition to molecular techniques that are being tested to improve the enzyme's characteristics and increase its expression rates. Moreover, as the native enzyme does not fulfill all of the process requirements, biopro‐ specting for new genes, rational engineering and directed evolution of known genes are

The authors acknowledge the financial support of Fapesp (Fundação de Amparo à Pesquisa

scale due to the health and fire hazards of methanol [35].

powerful tools that can be used to improve these enzymes.

*3.6.3. Expression in filamentous fungi*

successfully expressed in *A. oryzae* [120].

**4. Conclusion**

and 43 are still emerging.

**Acknowledgements**

do Estado de São Paulo).

F. L. Motta1\*, C. C. P. Andrade2 and M. H. A. Santana1

\*Address all correspondence to: flopesmotta@gmail.com

1 Development of Biotechnological Processes Laboratory, School of Chemical Engineering, University of Campinas, Campinas, Brazil

2 Bioprocess Engineering Laboratory, Food Engineering Department, University of Campinas, Campinas, Brazil
