Yee K.L.,Oak Ridge National Laboratory |
Yee K.L.,Genomatica |
Rodriguez M.,Oak Ridge National Laboratory |
Hamilton C.Y.,Oak Ridge National Laboratory |
And 7 more authors.
Consolidated bioprocessing (CBP), which merges enzyme production, biomass hydrolysis, and fermentation into a single step, has the potential to become an efficient and economic strategy for the bioconversion of lignocellulosic feedstocks to transportation fuels or chemicals. In this study, we evaluated wild-type Clostridium thermocellum, Caldicellulosiruptor bescii, and Caldicellulosiruptor obsidiansis, three thermophilic, cellulolytic, mixed-acid fermenting candidate CBP microorganisms, for their fermentation capabilities using dilute acid pretreated Populus as a model biomass feedstock. Under pH-controlled anaerobic fermentation conditions, each candidate successfully digested a minimum of 75 % of the cellulose from dilute acid pretreated Populus, as indicated by an increase in planktonic cells and end-product metabolites and a concurrent decrease in glucan content. C. thermocellum, which employs a cellulosomal approach to biomass degradation, required approximately 50 h to achieve 75 % cellulose utilization. In contrast, the noncellulosomal, secreted hydrolytic enzyme system of the Caldicellulosiruptor sp. required about 100 h after a significant lag phase to achieve similar results. End-point fermentation conversions for C. thermocellum, C. bescii, and C. obsidiansis were determined to be 0.29, 0.34, and 0.38 g of total metabolites per gram of loaded glucan, respectively. These data provide a starting point for future strain engineering efforts that can serve to improve the biomass fermentation capabilities of these three promising candidate CBP platforms. © 2015, Springer Science+Business Media New York. Source
Maselli O.J.,University of Adelaide |
Maselli O.J.,Dessert Research Institute |
Gascooke J.R.,University of Adelaide |
Gascooke J.R.,University of South Australia |
And 3 more authors.
Chemical Physics Letters
We explore the collisional energy transfer dynamics of benzene molecules spontaneously evaporating from an in vacuo water-ethanol liquid beam. We find that rotations are cooled significantly more than the lowest-energy vibrational modes, while the rotational energy distributions are Boltzmann. Within experimental uncertainty, the rotational temperatures of vibrationally-excited evaporating molecules are the same as the ground state. Collision-induced gas phase energy transfer measurements reveal that benzene undergoes fast rotational relaxation, from which we deduce that the rotational temperature measured in the evaporation experiments (200-230 K) is an indication of the translational energy of the evaporate. Conversely, vibrational relaxation of the high frequency mode, ν6, is very inefficient, suggesting that the ν6 temperature (260-270 K) is an indication of the liquid surface temperature. Modelling of the relaxation dynamics by both 'temperature gap' and 'Master Equation' approaches indicates that the equivalent of 150-260 hard-sphere collisions occur during the transition from liquid to vacuum. © 2011 Elsevier B.V. All rights reserved. Source