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3 Biotech (2011) 1:187–192 DOI 10.1007/s13205-011-0011-y

ORIGINAL ARTICLE

Synergy between EngE, XynA and ManA from Clostridium cellulovorans on corn stalk, grass and pineapple pulp substrates
B. Olver • J. S. Van Dyk • N. Beukes B. I. Pletschke
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Received: 19 April 2011 / Accepted: 24 May 2011 / Published online: 18 June 2011 Ó The Author(s) 2011. This article is published with openaccess at Springerlink.com

Abstract The synergistic interaction between various hemi/cellulolytic enzymes has become more important in order to achieve effective and optimal degradation of complex lignocellulose substrates for biofuel production. This study investigated the synergistic effect of three enzymes endoglucanase (EngE), mannanase (ManA) and xylanase (XynA) on the degradation of cornstalk, grass, and pineapple fruit pulp and determined the optimal degree of synergy between combinations of these enzymes. It was established that EngE was essential for degradation of all of the substrates, while the hemicellulases were able to contribute in a synergistic fashion to increase the activity on these substrates. Maximum specific activity and degree of synergy on the corn stalk and grasswas found with EngE:XynA in a ratio of 75:25%, with a specific activity of 41.1 U/mg protein and a degree of synergy of 6.3 for corn stalk, and 44.1 U/mg protein and 3.4 for grass, respectively. The pineapple fruit pulp was optimally digested using a ManA:EngE combination in a 50:50% ratio; the specific activity and degree of synergy achieved were 52.4 U/mg protein and 2.7, respectively. This studyhighlights the importance of hemicellulases for the synergistic degradation of complex lignocellulose. The inclusion of a mannanase in an enzyme consortium for biomass degradation should be examined further as this study suggests that it may play an important, although mostly overlooked, role in the synergistic saccharification of lignocellulose. Keywords Corn stalk Á EngE Á Grass Á ManA ÁPineapple pulp Á XynA
B. Olver Á J. S. Van Dyk Á N. Beukes Á B. I. Pletschke (&) Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, Grahamstown 6139, South Africa e-mail: B.Pletschke@ru.ac.za

Introduction Lignocellulose consists of approximately 75% carbohydrates which makes it an ideal feedstock for biofuel production (Bayer et al. 2007; Lynd et al. 1991). A whole rangeof enzymes is required to work in synergy to degrade these substrates. Synergy is established when the combined action of enzymes is greater than the sum of the individual activities on the same substrate. While synergy between cellulases on cellulose has been well studied (Andersen et al. 2008; Boisset et al. 2001; Teeri 1997; Woodward 1991) the synergy between cellulases and hemicellulases andbetween hemicellulases on their own has only recently garnered more attention (Banerjee et al. 2010; Gao et al. 2010; Prior and Day 2008; Selig et al. 2009). This is most probably because the main focus in biofuel production has been the production of glucose which is the optimal substrate for ethanol fermentation in prominent fermentation organisms such as Saccharomyces cerevisiae (Himmel et al.2007). However, ignoring the hemicellulose fraction of a lignocellulose substrate for eventual fermentation reduces the total yield of sugars obtainable (Merino and Cherry 2007). The hemicellulose fraction and its saccharification have therefore gained prominence even though it may only form a small percentage of the carbohydrates in the substrate. Thus, hemicellulases such as xylanases andmannanases are increasingly being investigated for their role in enhancing the saccharification of substrates and increasing the overall yield of sugars obtained. The enzymes in this study are all cellulosomal enzymes derived from Clostridium cellulovorans. EngE is a glycosyl hydrolase family 5 endoglucanase and is one of the three major subunits of the C. cellulovorans cellulosome (Tamaru and Doi 1999)....