concentration in algal biomass ranges from 6 to 12% for an
early harvest, fully nutrient replete grown culture, to between
1 and 5% for biomass harvested from a nutrient deplete grown
culture.
7. Quality control: A report should always include both the nitrogen and the calculated protein content with the respective
conversion factor. The average of replicate measurements as
well as the relative standard deviation (RSD) and the relative
percent different (RPD) between samples should be included
in a report. Every analysis should include a reagent blank, a
standard such as EDTA, and ideally triplicates of a QC sample
in each run. Choosing QC samples should be done by matching the nitrogen concentration levels and matrices of QC samples to the samples in the run. The overall accuracy of system is
demonstrated by making 10 successive determinations of nitrogen in EDTA or another reference standard and 10 successive
determinations in a QC algal biomass material. If an EDTA
sample within the run is more than Æ0.2 from its calculated
protein equivalent, a drift correction is performed. Means of
determinations must be within 0.15 of the respective theoretical values, with standard deviations 0.15. An acceptable average
standard deviation among replicated analyses for crude protein
(CP) ranges from about 0.10 for samples with 10% CP to 0.20
for samples with 20% CP, which results in warning limits (2Â
standard deviation) ranging from 0.20 to 0.40 and control
limits (3Â standard deviation) ranging from 0.30 to 0.60.
Plot the results of the control sample(s) on a X-control chart
and examine the chart for trends. Results outside of upper or
lower warning limits, or 2Â standard deviation (95% confidence limits), are evidence of possible problems with the analytical system. Results outside of upper or lower control limits,
or 3Â standard deviation (99% confidence limits), indicate loss
of control and results of the run should be discarded. Two
consecutive analyses falling on one side of the mean between
the warning limits and the control limits also indicate loss of
control.
8. Amino acid make up and respective nitrogen concentration in
each amino acid can be used to derive a nitrogen-to-protein
conversion factor. Typically for an algal biomass sample for a
new species of algae the total amino acid profile should be
determined. In addition to a typical 24 h HCl hydrolysis for
full protein hydrolysis to constituent amino acids, separate
hydrolyses are needed for tryptophan (Trp) and for the sulfur
containing AAs (Met and Cys). Two additional hydrolysis time
points (12 and 48 h) are run to account for AAs (Thr, Ser, and
238
L. M. L. Laurens et al.
early harvest, fully nutrient replete grown culture, to between
1 and 5% for biomass harvested from a nutrient deplete grown
culture.
7. Quality control: A report should always include both the nitrogen and the calculated protein content with the respective
conversion factor. The average of replicate measurements as
well as the relative standard deviation (RSD) and the relative
percent different (RPD) between samples should be included
in a report. Every analysis should include a reagent blank, a
standard such as EDTA, and ideally triplicates of a QC sample
in each run. Choosing QC samples should be done by matching the nitrogen concentration levels and matrices of QC samples to the samples in the run. The overall accuracy of system is
demonstrated by making 10 successive determinations of nitrogen in EDTA or another reference standard and 10 successive
determinations in a QC algal biomass material. If an EDTA
sample within the run is more than Æ0.2 from its calculated
protein equivalent, a drift correction is performed. Means of
determinations must be within 0.15 of the respective theoretical values, with standard deviations 0.15. An acceptable average
standard deviation among replicated analyses for crude protein
(CP) ranges from about 0.10 for samples with 10% CP to 0.20
for samples with 20% CP, which results in warning limits (2Â
standard deviation) ranging from 0.20 to 0.40 and control
limits (3Â standard deviation) ranging from 0.30 to 0.60.
Plot the results of the control sample(s) on a X-control chart
and examine the chart for trends. Results outside of upper or
lower warning limits, or 2Â standard deviation (95% confidence limits), are evidence of possible problems with the analytical system. Results outside of upper or lower control limits,
or 3Â standard deviation (99% confidence limits), indicate loss
of control and results of the run should be discarded. Two
consecutive analyses falling on one side of the mean between
the warning limits and the control limits also indicate loss of
control.
8. Amino acid make up and respective nitrogen concentration in
each amino acid can be used to derive a nitrogen-to-protein
conversion factor. Typically for an algal biomass sample for a
new species of algae the total amino acid profile should be
determined. In addition to a typical 24 h HCl hydrolysis for
full protein hydrolysis to constituent amino acids, separate
hydrolyses are needed for tryptophan (Trp) and for the sulfur
containing AAs (Met and Cys). Two additional hydrolysis time
points (12 and 48 h) are run to account for AAs (Thr, Ser, and
238
L. M. L. Laurens et al.