Thermostable endoglucanases in the liquefaction of hydrothermally pretreated wheat straw.
BACKGROUND
Thermostable enzymes have several benefits in lignocellulose processing. In particular, they potentially allow the use of increased substrate concentrations (because the substrate viscosity decreases as the temperature increases), resulting in improved product yields and reduced capital and processing costs. A short pre-hydrolysis step at an elevated temperature using thermostable enzymes aimed at rapid liquefaction of the feedstock is seen as an attractive way to overcome the technical problems (such as poor mixing and mass transfer properties) connected with high initial solid loadings in the lignocellulose to ethanol process.


RESULTS
The capability of novel thermostable enzymes to reduce the viscosity of high-solid biomass suspensions using a real-time viscometric measurement method was investigated. Heterologously expressed enzymes from various thermophilic organisms were compared for their ability to liquefy the lignocellulosic substrate, hydrothermally pretreated wheat straw. Once the best enzymes were identified, the optimal temperatures for these enzymes to decrease substrate viscosity were compared. The combined hydrolytic properties of the thermostable preparations were tested in hydrolysis experiments. The studied mixtures were primarily designed to have good liquefaction potential, and therefore contained an enhanced proportion of the key liquefying enzyme, EGII/Cel5A.


CONCLUSIONS
Endoglucanases were shown to have a superior ability to rapidly reduce the viscosity of the 15% (w/w; dry matter) hydrothermally pretreated wheat straw. Based on temperature profiling studies, Thermoascus aurantiacus EGII/Cel5A was the most promising enzyme for biomass liquefaction. Even though they were not optimized for saccharification, many of the thermostable enzyme mixtures had superior hydrolytic properties compared with the commercial reference enzymes at 55°C.
University of Helsinki, Department of Food and Environmental Sciences, P,O, Box 27, FIN-00014, Helsinki, Finland. nora.szijarto@helsinki.fi.
Nóra
N
Szijártó
Emma
E
Horan
Junhua
J
Zhang
Terhi
T
Puranen
Matti
M
Siika-Aho
Liisa
L
Viikari
Appl Biochem Biotechnol. 2010 Jan;160(2):360-9
18626577
Biotechnol Bioeng. 2008 Oct 15;101(3):515-28
18512263
Appl Microbiol Biotechnol. 2006 Feb;69(6):627-42
16331454
Appl Biochem Biotechnol. 2003 Spring;105 -108:383-92
12721461
J Biotechnol. 2000 Mar 10;78(2):149-61
10725538
Bioresour Technol. 2010 Apr;101(7):2405-11
20006928
J Biotechnol. 2000 Feb 28;78(1):39-48
10702909
Curr Opin Biotechnol. 2009 Jun;20(3):372-80
19502048
Bioresour Technol. 2009 Jan;100(2):925-34
18760597
Appl Microbiol Biotechnol. 2005 Jun;67(4):495-505
15650852
Biotechnol Bioeng. 2007 Apr 1;96(5):862-70
16865734
Appl Biochem Biotechnol. 2010 Feb;160(4):1102-15
19333558
Biotechnol Bioeng. 2009 Oct 1;104(2):290-300
19472300
Bioresour Technol. 2009 Jan;100(1):10-8
18599291
Adv Biochem Eng Biotechnol. 2007;108:121-45
17589813
Bioresour Technol. 2011 Jan;102(2):1968-74
20884202
Appl Biochem Biotechnol. 2004 Spring;113-116:723-32
15054288
Bioresour Technol. 2005 Apr;96(6):673-86
15588770
Bioresour Technol. 2007 Sep;98(12):2415-57
17336061
Appl Biochem Biotechnol. 1998 Spring;70-72:395-403
9627391
Biotechnol Prog. 2003 Jul-Aug;19(4):1109-17
12892470
Bioresour Technol. 2010 Jul;101(13):4842-50
20194021
Biotechnol Bioeng. 2007 Aug 1;97(5):1028-38
17221887