9 research outputs found
Feasibility of Spectroscopic Characterization of Algal Lipids: Chemometric Correlation of NIR and FTIR Spectra with Exogenous Lipids in Algal Biomass
Accurate and reliable quantification of total microalgal fuel potential as fatty acid methyl esters by in situ transesterification
In the context of algal biofuels, lipids, or better aliphatic chains of the fatty acids, are perhaps the most important constituents of algal biomass. Accurate quantification of lipids and their respective fuel yield is crucial for comparison of algal strains and growth conditions and for process monitoring. As an alternative to traditional solvent-based lipid extraction procedures, we have developed a robust whole-biomass in situ transesterification procedure for quantification of algal lipids (as fatty acid methyl esters, FAMEs) that (a) can be carried out on a small scale (using 4–7 mg of biomass), (b) is applicable to a range of different species, (c) consists of a single-step reaction, (d) is robust over a range of different temperature and time combinations, and (e) tolerant to at least 50% water in the biomass. Unlike gravimetric lipid quantification, which can over- or underestimate the lipid content, whole biomass transesterification reflects the true potential fuel yield of algal biomass. We report here on the comparison of the yield of FAMEs by using different catalysts and catalyst combinations, with the acid catalyst HCl providing a consistently high level of conversion of fatty acids with a precision of 1.9% relative standard deviation. We investigate the influence of reaction time, temperature, and biomass water content on the measured FAME content and profile for 4 different samples of algae (replete and deplete Chlorella vulgaris, replete Phaeodactylum tricornutum, and replete Nannochloropsis sp.). We conclude by demonstrating a full mass balance closure of all fatty acids around a traditional lipid extraction process
Starch metabolism in maize leaves
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Fatty Amide Determination in Neutral Molecular Fractions of Green Crude Hydrothermal Liquefaction Oils From Algal Biomass
Even though hydrothermal liquefaction (HTL) is a promising route
to produce crude oils (referred to as “green crude”),
the molecular composition of the nitrogen fraction of such green crude
oils is not fully understood. The goal of this work was to identify
and quantify the fraction of fatty amides in green crude oils obtained
from five different samples derived from Desmodesmus
armatus, Tetraselmis sp., and Chlorella sp. biomass treated
under different HTL conditions (260 or 340 °C as batch or continuous
processes). The goal of this work was to elucidate the nature of the
high nitrogen content of the green crude oils. We identified at least
19 distinct fatty amides present in green crude oils and quantified
them based on relevant standards in purified fractions after functional
group-based separation and enrichment. It was not known how much these
compounds contributed to the oils or which molecular fraction they
are associated with. We found that fatty amides exclusively partitioned
with the neutral fraction of the oils and belonged mainly to one of
five categories, based on their functional group substitution, i.e.,
fatty amides, monomethyl, dimethyl, monoethanolamide, and diethanolamide.
The quantification of fatty amides in the neutral oil fraction was
based on respective fatty amide standards, after verification of consistency
in response factors between molecules with different substitutions
of the amide group. We found that the amount of fatty amides found
in each of the five samples varied considerably and ranged between
1.4 and 3.0% of the green crude oils, with the highest levels detected
in the sample with the highest oil content, after HTL of biomass derived
from a nutrient deprived Chlorella sp.
culture
Mechanism, kinetics and microbiology of inhibition caused by long-chain fatty acids in anaerobic digestion of algal biomass
BACKGROUND: Oleaginous microalgae contain a high level of lipids, which can be extracted and converted to biofuel. The lipid-extracted residue can then be further utilized through anaerobic digestion to produce biogas. However, long-chain fatty acids (LCFAs) have been identified as the main inhibitory factor on microbial activity of anaerobic consortium. In this study, the mechanism of LCFA inhibition on anaerobic digestion of whole and lipid-extracted algal biomass was investigated with a range of calcium concentrations against various inoculum to substrate ratios as a means to alleviate the LCFA inhibition. RESULTS: Whole algal biomass of Nannochloropsissalina represents high lipid content algal biomass while lipid-extracted residue represents its low lipid counterpart. The anaerobic digestion experiments were conducted in a series of serum bottles at 35 °C for 20 days. A kinetic model, considering LCFA inhibition on hydrolysis, acidogenesis as well as methanogenesis steps, was developed from the observed phenomenon of inhibition factors as a function of the LCFA concentration and specific biomass content or calcium concentration. The results showed that inoculum to substrate ratio had a stronger effect on biogas production than calcium, and calcium had no effect on biogas production when inoculum concentration was extremely low. The microbial community analysis by high-throughput Illumina Miseq sequencing indicated that diversity of both bacterial and methanogenic communities decreased with elevation of lipid concentration. Hydrolytic bacteria and aceticlastic methanogens dominated bacterial and archaea communities, respectively, in both high and low LCFA concentration digesters. CONCLUSIONS: This study demonstrated that inoculum concentration has a more significant effect on alleviating LCFA inhibition than calcium concentration, while calcium only played a role when inoculum concentration met a threshold level. The model revealed that each functional microbial group was subject to different levels of LCFA inhibition. Although methanogens were the most susceptible microbes to LCFA inhibition, the inhibition factor for hydrolytic bacteria was more highly affected by inoculum concentration. The microbial community analysis indicated that the bacterial community was affected more than the methanogenic community by high LCFAs concentration. Syntrophic acetogens were sensitive to high LCFA concentrations and thus showed a decreased abundance in such an environment. [Figure: see text
Profiling <i>Chlamydomonas</i> Metabolism under Dark, Anoxic H<sub>2</sub>‑Producing Conditions Using a Combined Proteomic, Transcriptomic, and Metabolomic Approach
<i>Chlamydomonas reinhardtii</i> is well adapted to survive
under different environmental conditions due to the unique flexibility
of its metabolism. Here we report metabolic pathways that are active
during acclimation to anoxia, but were previously not thoroughly studied
under dark, anoxic H<sub>2</sub>-producing conditions in this model
green alga. Proteomic analyses, using 2D-differential in-gel electrophoresis
in combination with shotgun mass fingerprinting, revealed increased
levels of proteins involved in the glycolytic pathway downstream of
3-phosphoglycerate, the glyoxylate pathway, and steps of the tricarboxylic
acid (TCA) reactions. Upregulation of the enzyme, isocitrate lyase
(ICL), was observed, which was accompanied by increased intracellular
succinate levels, suggesting the functioning of glyoxylate pathway
reactions. The ICL-inhibitor study revealed presence of reverse TCA
reactions under these conditions. Contributions of the serine-isocitrate
lyase pathway, glycine cleavage system, and c1-THF/serine hydroxymethyltransferase
pathway in the acclimation to dark anoxia were found. We also observed
increased levels of amino acids (AAs) suggesting nitrogen reorganization
in the form of de novo AA biosynthesis during anoxia. Overall, novel
routes for reductant utilization, in combination with redistribution
of carbon and nitrogen, are used by this alga during acclimation to
O<sub>2</sub> deprivation in the dark
Algal Biomass Constituent Analysis: Method Uncertainties and Investigation of the Underlying Measuring Chemistries
Algal biomass compositional analysis data form the basis
of a large
number of techno-economic process analysis models that are used to
investigate and compare different processes in algal biofuels production.
However, the analytical methods used to generate these data are far
from standardized. This work investigated the applicability of common
methods for rapid chemical analysis of biomass samples with respect
to accuracy and precision. This study measured lipids, protein, carbohydrates,
ash, and moisture of a single algal biomass sample at 3 institutions
by 8 independent researchers over 12 separate workdays. Results show
statistically significant differences in the results from a given
analytical method among laboratories but not between analysts at individual
laboratories, suggesting consistent training is a critical issue for
empirical analytical methods. Significantly different results from
multiple lipid and protein measurements were found to be due to different
measurement chemistries. We identified a set of compositional analysis
procedures that are in best agreement with data obtained by more advanced
analytical procedures. The methods described here and used for the
round robin experiment do not require specialized instrumentation,
and with detailed analytical documentation, the differences between
laboratories can be markedly reduced