Enzymes for biofuels research


Enzymes for biofuels research

Cellulases

Cellulases are a particularly confusing group of enzymes (for some cellulase clarity, I suggest checking out our review article on bacterial cellulases here).  Cellulases are classified into two categories, endocellulases and exocellulases (Figure 1).  Endocellulases cleave randomly in the center of cellulose chains; an example of an endocellulase is T. reesei EG1 as well as a number of C. thermocellum cellulases.  Exocellulases cleave at the ends of the cellulose chains, generating either cellobiose (cellobiohydrolases) or glucose (β-glucosidase).  Cellobiohydrolases are further classified by the end of the chain from which they generate cellobiose, reducing end cellobiohydrolases and non-reducing end cellobiohydrolases.  β-Glucosidases cleave only from the non-reducing end of the chain.

Figure 1

C5-6 supplies a wide range of cellulases from a variety of organisms.  Among the enzymes available are endocellulases – T. reesei EG1 , C. thermocellum CelE, CelD, CelH, CelL, CelC, D. turgidum CelA, and A. cellulolyticus Cellulase 40 (Acel_0615). Cellobiohydrolases are also available from a range of organisms – T. reesei CBHI and CBHII,and  C. thermocellum CelA, CelI, CelK, CelR,and CbhA.  Other available cellulases have not been classified by  category, including enzymes from A. cellulolyticusCellulomonas species, and F. succinogenes. C5-6 supplies β-glucosidases  from the widest range of organisms including T. reesei , C. thermocellum, B. cellulosilyticus, F. succinogenes, D. turgidum, and Geobacillus  species.  The most popular β-glucosidase with our customers is the A. acidocaldarius β-glucosidase.  Still have questions about cellulases?  Drop us a line and we’ll be happy to help you out.

 

 Enzymes for xyloglucan degradation

Xyloglucan consists of  β-1,4 linked glucose chains, similar to cellulose, substituted with α-1,6 linked xylose.  Depending on the plant source, the xylose can be further substituted with galactose or galactose and fucose.  Xyloglucanases cleave the β-1,4 linkages in xyloglucan.  Most endocellulases and β-glucanases cannot cleave xyloglucan, however exceptions exist.  The xylose resiudes can be cleaved from xyloglucan using an α-xylosidase (Figure 2).   β-Glucosidases cleave glucose from the non-reducing end of the chain.

Figure 2

Xyloglucan

 C5-6 supplies a number of enzymes with xyloglucanase activity including Streptomyces flavogriseus xyloglucanase  and F. succinogenes xyloglucanase.  Other available enzymes with xyloglucanase activity include D. turgidum CelA and C. thermocellum CelD, CelE and CelH.  C5-6 is the only supplier of  fungal α-xylosidase from A. niger.  The most popular β-glucosidase with our customers is the A. acidocaldarius β-glucosidase.  

Enzymes for xylan degradation

Xylan contains a backbone of  β-1,4 linked xylose residues.  Depending on the source, the backbone can be substituted with α-1,2 linked glucuronic acid (glucuronoxylan, GX), α-1,2 and  α-1,3 linked arabinose (arabinoxylan, AX) or α-1,2 linked glucuronic acid and  α-1,3 linked arabinose (glucuronoarabinoxylan, GAX) (Figure 3).  Additional substitutions such as acetyl and methyl groups can be present, and the material can be crosslinked to components of lignin such as ferrulic acid.  Xylanases (technically endoxylanases) cleave β-1,4 xylose linkages in the backbone.  β-xylosidases cleave xylose from the nonreducing end of the xylan chain.  α-Glucuronidases cleave the α-1,2 linked glucuronic acid from the backbone and α-arabinosidases (arabinofuranosidases) cleave the α-1,2 and  α-1,3 linked arabinose from the backbone.

Figure 3  

 

Xylan

 C5-6 supplies a complete set of xylan-degrading activities to advance your research.  Xylanases from C. thermocellumD. turgidum, and Geobacillus sp. all possess the stability to work under the conditions of  biomass pretreatment. A wide range of thermostable bacterial β-xylosidases,  α-glucuronidases, and α-arabinosidases are also available that complement these bacterial xylanases.  Many of these enzymes are available only through C-6.  A number of these thermostable bacterial enzymes have been shown to be superior to their fungal counterparts in producing both xylose and glucose from pretreated biomass (Gao D, Chundawat S, Liu T, Hermanson S, Gowda K, Brumm P, Dale BE, Balan V. Strategy for identification of novel fungal and bacterial glycosyl hydrolase hybrid mixtures that can efficiently saccharify pretreated lignocellulosic biomass. Bioenergy Research. 2010. 3(1):67-8).   All these enzymes can be easily scaled-up for pilot and production testing. C5-6 is also the only source for the full set of T. reesei xylan-degrading enzymes (xylanases, β-xylosidase,  α-glucuronidase, and α-arabinosidase).