Cellulose utilization by Clostridium thermocellum: Bioenergetics and hydrolysis product assimilation Export

@article{citeulike:1911977, abstract = {The bioenergetics of cellulose utilization by Clostridium thermocellum was investigated. Cell yield and maintenance parameters, [IMG]f1.gif" BORDER="0"> g cell/mol ATP and m = 3.27 mmol ATP/g cell per hour, were obtained from cellobiose-grown chemostats, and it was shown that one ATP is required per glucan transported. Experimentally determined values for [IMG]f2.gif" BORDER="0"> (ATP from phosphorolytic {beta}-glucan cleavage minus ATP for substrate transport, mol ATP/mol hexose) from chemostats fed {beta}-glucans with degree of polymerization (DP) 2-6 agreed well with the predicted value of (n-1)/n (n = mean cellodextrin DP assimilated). A mean [IMG]f2.gif" BORDER="0"> value of 0.52 {+/-} 0.06 was calculated for cellulose-grown chemostat cultures, corresponding to n = 4.20 {+/-} 0.46. Determination of intracellular {beta}-glucan radioactivity resulting from 14C-labeled substrates showed that uptake is different for cellulose and cellobiose (G2). For 14C-cellobiose, radioactivity was greatest for G2; substantially smaller but measurable for G1, G3, and G4; undetectable for G5 and G6; and n was {approx}2. For 14C-cellulose, radioactivity was greatest for G5; lower but substantial for G6, G2, and G1; very low for G3 and G4; and n was {approx}4. These results indicate that: (i) C. thermocellum hydrolyzes cellulose by a different mode of action from the classical mechanism involving solubilization by cellobiohydrolase; (ii) bioenergetic benefits specific to growth on cellulose are realized, resulting from the efficiency of oligosaccharide uptake combined with intracellular phosphorolytic cleavage of {beta}-glucosidic bonds; and (iii) these benefits exceed the bioenergetic cost of cellulase synthesis, supporting the feasibility of anaerobic biotechnological processing of cellulosic biomass without added saccharolytic enzymes. 10.1073/pnas.0408734102}, author = {Zhang, Yi-Heng P. and Lynd, Lee R.}, citeulike-article-id = {1911977}, citeulike-linkout-0 = {http://dx.doi.org/10.1073/pnas.0408734102}, citeulike-linkout-1 = {http://www.pnas.org/content/102/20/7321.abstract}, citeulike-linkout-2 = {http://www.pnas.org/content/102/20/7321.full.pdf}, citeulike-linkout-3 = {http://www.pnas.org/cgi/content/abstract/102/20/7321}, citeulike-linkout-4 = {http://view.ncbi.nlm.nih.gov/pubmed/15883376}, citeulike-linkout-5 = {http://www.hubmed.org/display.cgi?uids=15883376}, day = {17}, doi = {10.1073/pnas.0408734102}, journal = {Proceedings of the National Academy of Sciences}, keywords = {assimilation, bioenergetics, cellulose, clostridium, hydrolysis, thermocellum, utilization}, month = {May}, number = {20}, pages = {7321--7325}, posted-at = {2009-04-27 14:03:30}, priority = {2}, title = {Cellulose utilization by Clostridium thermocellum: Bioenergetics and hydrolysis product assimilation}, url = {http://dx.doi.org/10.1073/pnas.0408734102}, volume = {102}, year = {2005} }

TY - JOUR ID - citeulike:1911977 L3 - citeulike-article-id:1911977 N2 - The bioenergetics of cellulose utilization by Clostridium thermocellum was investigated. Cell yield and maintenance parameters, [IMG]f1.gif" BORDER="0"> g cell/mol ATP and m = 3.27 mmol ATP/g cell per hour, were obtained from cellobiose-grown chemostats, and it was shown that one ATP is required per glucan transported. Experimentally determined values for [IMG]f2.gif" BORDER="0"> (ATP from phosphorolytic {beta}-glucan cleavage minus ATP for substrate transport, mol ATP/mol hexose) from chemostats fed {beta}-glucans with degree of polymerization (DP) 2-6 agreed well with the predicted value of (n-1)/n (n = mean cellodextrin DP assimilated). A mean [IMG]f2.gif" BORDER="0"> value of 0.52 {+/-} 0.06 was calculated for cellulose-grown chemostat cultures, corresponding to n = 4.20 {+/-} 0.46. Determination of intracellular {beta}-glucan radioactivity resulting from 14C-labeled substrates showed that uptake is different for cellulose and cellobiose (G2). For 14C-cellobiose, radioactivity was greatest for G2; substantially smaller but measurable for G1, G3, and G4; undetectable for G5 and G6; and n was {approx}2. For 14C-cellulose, radioactivity was greatest for G5; lower but substantial for G6, G2, and G1; very low for G3 and G4; and n was {approx}4. These results indicate that: (i) C. thermocellum hydrolyzes cellulose by a different mode of action from the classical mechanism involving solubilization by cellobiohydrolase; (ii) bioenergetic benefits specific to growth on cellulose are realized, resulting from the efficiency of oligosaccharide uptake combined with intracellular phosphorolytic cleavage of {beta}-glucosidic bonds; and (iii) these benefits exceed the bioenergetic cost of cellulase synthesis, supporting the feasibility of anaerobic biotechnological processing of cellulosic biomass without added saccharolytic enzymes. 10.1073/pnas.0408734102 IS - 20 JF - Proceedings of the National Academy of Sciences EP - 7325 TI - Cellulose utilization by Clostridium thermocellum: Bioenergetics and hydrolysis product assimilation VL - 102 SP - 7321 KW - assimilation KW - bioenergetics KW - cellulose KW - clostridium KW - hydrolysis KW - thermocellum KW - utilization AU - Zhang, Yi-Heng AU - Lynd, Lee PY - 2005/05/17/ UR - http://dx.doi.org/10.1073/pnas.0408734102 ER -