Accurate and reliable structural characterization of
technical
lignins is still challenging and inhibits industrial utilization as
only poor understanding of structure–property relationship
is available. Especially, molar mass analysis of technical lignins
is of paramount interest; however, the usage of conventional size
exclusion chromatography (SEC) and synthetic polymer standards as
a consequence of inaccessible lignin standards is predominantly found
in academia. This leads to a huge discrepancy in molecular weight
analyses of lignins between different laboratories and consequently
to fragile comparability. In this study, organosolv (OS) lignin from
beech wood was exemplarily used to develop and evaluate a new acetone–water-based
SEC method with the ability to be coupled to an electrospray ionization-mass
spectrometer (ESI-MS) or to a multi-angle light scattering detector
(MALLS or short MALS). The eluent system used shows very good solubility
for the lignins investigated and hence lowers the probability for
molecular aggregation of lignin molecules in solution. Solvent fractionation
in acetone–water mixtures was conducted to acquire molecular
weight classes. The starting lignin (parent lignin) was initially
dissolved in 80 wt % acetone–water. Various fractions of the
parent lignin were produced by a stepwise reduction of the acetone
content. Molecular weights based on narrow polyethylene glycol (PEG)/polyethylene
oxide (PEO) standards and absolute molar masses by coupling SEC with
MALS were obtained, and the drawback of using polymer standards is
discussed in detail. At a lower acetone content, low-molecular-weight
fractions were found. Additionally, the specific refractive index
increments (dn/dc) were determined
for the parent lignin and its fractions. The impact of dn/dc on the final molecular weight (M
W) was evaluated considering the chemical composition
obtained by nuclear magnetic resonance spectroscopy (NMR) analysis.
Furthermore, light scattering revealed that the absorption behavior
for this OS lignin is low and neglectable. This article proposes a
new acetone-based analytical method for direct determination of absolute
molar masses of OS lignin molecules.
glucose when using hydrolyzed straw and ryegrass supplemented with medium, respectively. These results are similar to the hydrogen yields when using Thermotoga basal medium with glucose (TBGY) as control group.In order to minimize the supplementation of the hydrolysate and thus increase the economic efficiency of the process, the essential media components were identified. The experiments revealed NaCl, KCl, and glucose as essential components for cell growth as well as biohydrogen production. When excluding NaCl, a decrease of 96 % in hydrogen production occured.
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