Methods in Molecular Biology (2020) 1980: 233–242
DOI 10.1007/7651_2018_126
© Springer Science+Business Media New York 2018
Published online: 20 April 2018
Total Protein Content Determination of Microalgal Biomass
by Elemental Nitrogen Analysis and a Dedicated Nitrogento-Protein Conversion Factor
L. M. L. Laurens, J. L. Olstad, and D. W. Templeton
Abstract
Accurately determining protein content is important in the valorization of algal biomass in food, feed, and
fuel markets, where these values are used for component balance calculations. Conversion of elemental
nitrogen to protein is a well-accepted and widely practiced method, but depends on developing an
applicable nitrogen-to-protein conversion factor. The methodology reported here covers the quantitative
assessment of the total nitrogen content of algal biomass and a description of the methodology that
underpins the accurate de novo calculation of a dedicated nitrogen-to-protein conversion factor.
Keywords Amino acids, Nitrogen analysis, Nitrogen-to-protein conversion factor, Protein
1 Introduction
The protein content of algae has a strong influence in determining
potential food, feed, co-product, and fuel uses for algal biomass.
The protein content of microalgae can range from 7 to 40% [1–4]
and can change dramatically over the course of the algae lifecycle.
One source of biomass that is currently commercialized for food
supplement sale is Spirulina, thanks to the high protein content
(reported to be 50–60% of the biomass) [5].
Spectrophotometric protein measurement methods are ubiquitously used throughout the literature and can be useful for generating relative protein data or concentrations of protein in purified
extract. However, colorimetric methods are significantly less useful
for determining absolute protein values in complex materials such
as whole algal biomass, where the values are important for component balance calculations. In the case of the Lowry spectrophotometric procedure, the color development is based on the reduction
of the Folin reagent (Cu2+ to Cu+) by aromatic residues and
peptide bonds in protein, after which the Cu+ is chelated by
bicinchoninic acid (BCA) to form the detected color [6–8]. Perhaps
233
DOI 10.1007/7651_2018_126
© Springer Science+Business Media New York 2018
Published online: 20 April 2018
Total Protein Content Determination of Microalgal Biomass
by Elemental Nitrogen Analysis and a Dedicated Nitrogento-Protein Conversion Factor
L. M. L. Laurens, J. L. Olstad, and D. W. Templeton
Abstract
Accurately determining protein content is important in the valorization of algal biomass in food, feed, and
fuel markets, where these values are used for component balance calculations. Conversion of elemental
nitrogen to protein is a well-accepted and widely practiced method, but depends on developing an
applicable nitrogen-to-protein conversion factor. The methodology reported here covers the quantitative
assessment of the total nitrogen content of algal biomass and a description of the methodology that
underpins the accurate de novo calculation of a dedicated nitrogen-to-protein conversion factor.
Keywords Amino acids, Nitrogen analysis, Nitrogen-to-protein conversion factor, Protein
1 Introduction
The protein content of algae has a strong influence in determining
potential food, feed, co-product, and fuel uses for algal biomass.
The protein content of microalgae can range from 7 to 40% [1–4]
and can change dramatically over the course of the algae lifecycle.
One source of biomass that is currently commercialized for food
supplement sale is Spirulina, thanks to the high protein content
(reported to be 50–60% of the biomass) [5].
Spectrophotometric protein measurement methods are ubiquitously used throughout the literature and can be useful for generating relative protein data or concentrations of protein in purified
extract. However, colorimetric methods are significantly less useful
for determining absolute protein values in complex materials such
as whole algal biomass, where the values are important for component balance calculations. In the case of the Lowry spectrophotometric procedure, the color development is based on the reduction
of the Folin reagent (Cu2+ to Cu+) by aromatic residues and
peptide bonds in protein, after which the Cu+ is chelated by
bicinchoninic acid (BCA) to form the detected color [6–8]. Perhaps
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