CHEMICAL ENGINEERING TRANSACTIONS VOL. 80, 2020 A publication of The Italian Association of Chemical Engineering Online at www.cetjournal.it Guest Editors: Eliseo Maria Ranzi, Rubens Maciel Filho Copyright © 2020, AIDIC Servizi S.r.l. I SBN 978-88-95608-78-5; I SSN 2283-9216 Use of FTIR Spectroscopy and PLS-Regression in Monitoring Biomolecules in Spirulina platensis during its Growth in an Internally-Illuminated Photobioreactor Butch G. Bataller a, *, Sergio C. Capareda b a University of the Philippines Los Baños, Laguna, Philippines b Texas A&M University, Texas, USA bgbataller@up.edu.ph This study developed a rapid and non-destructive analytical method for biochemical analysis of the Spirulina biomass via FTIR spectroscopy and PLS regression. It was then used to monitor the biochemical changes in the biomass during an 8-day cultivation period in a 3-L internally-illuminated concentric-tube airlift photobioreactor at different light intensities (69, 110, and 166 μmol photons m -2 s -1 ). It was found that PLS- regression have better predictive power than multipoint regression. It also yielded statistically similar results with conventional biochemical methods. This new method reduced the time for sample preparation and eliminated the extraction of target biomolecule for analysis. It was also found to be valuable in monitoring the changes in the total protein, carbohydrate and lipid content (% w/w of total biomolecules) in Spirulina biomass during its growth. It was observed that the protein content of the biomass decreased initially, which was compensated by an increase in the carbohydrate content. This may imply that biomass production may be driven by production of more carbohydrates during the early period of growth. Protein content then started to increase until the third day of growth and remained constant thereafter. Carbohydrate and lipid content also remained constant from the third day of growth. The lowest light intensity was found to have the highest protein content (60.4± 0.87 %w/w) but it has the lowest overall biomass productivity (0.090 ± 0.017 g L -1 d -1 ). While at the highest light intensity, protein content was slightly lower (57.3 ± 0.777 %w/w) than that of the lowest light intensity. But it has the highest overall biomass productivity (0.141 ±0.007 g L -1 d -1 ). 1. Introduction Conventional biochemical methods in quantifying biomolecules such as proteins, carbohydrates, and lipids in algal biomass are usually time-consuming due to the series of steps that need to be undertaken during the analysis. These steps usually require sample preparation and extraction steps before measurement can be done. In extracting the target analyte, conventional biochemical methods often require high temperature that may be destructive to the sample. For example, the proteins are extracted from the biomass at high temperature using alkaline solution or a detergent-containing buffer. To prevent underestimation of protein content, several extraction steps are necessary to ensure maximum extraction of protein. In carbohydrate analysis via the phenol-sulfuric acid method, breaking down the polysaccharides and oligosaccharides to their constituent monosaccharides often uses strong acids and often takes four hours in boiling water baths. These methods also often require toxic and corrosive reagents that are harmful to human health and the environment. These methods are also sensitive to other interfering substances. For example, Lowry assay for protein analysis is sensitive to the presence of carbohydrate, glycerol, and EDTA that are typically present in algal extracts or in extraction buffers (Quiang and Richmond 2013). Detergents like sodium dodecyl sulfate and Triton X-100 may also interfere with color development in Bradford protein assay. Overestimation of protein may also result due to high presence of arginine and/or phenylalanine that bind disproportionately with the Coomassie Brilliant Blue G250 dye (Quiang and Richmond 2013). Phenol-sulfuric acid method for DOI: 10.3303/CET2080018 Paper Received: 13 November 2019; Revised: 3 February 2020; Accepted: 29 April 2020 Please cite this article as: Bataller B., Capareda S., 2020, Use of Ftir Spectroscopy and Pls-regression in Monitoring Biomolecules in Spirulina Platensis During Its Growth in an Internally-illuminated Photobioreactor , Chemical Engineering Transactions, 80, 103-108 DOI:10.3303/CET2080018 103