A new approach for the detection and quantification of microalgae in industrial-scale microalgal cultures

Abstract

In industrial-scale cultures, non-target microalgae compete with the desired species for nutrients and CO2, thus reducing the growth rate of the target species and the quality of the produced biomass. Microalgae identification is generally considered a complicated issue although, in the last few years, new molecular methods have helped to rectify this problem. Of the different techniques available, DNA barcoding has proven very useful in providing rapid, accurate and automatable species identification; in this work, it is used to assess the genomic identity of the microalga species Scenedesmus almeriensis, a common strain in industrial-scale cultures. Barcode markers rbcL and ITS1-5.8S-ITS2 were sequenced and the obtained genomic information was used to design a quantitative PCR assay to precisely quantify the S. almeriensis concentration in microalgal cultures of industrial interest. TaqMan chemistry was used to quantify down to 1 µg/L dry weight of S. almeriensis cells, as well as to detect the presence of other concentrated microalgae cultures. A simple direct PCR approach was also investigated to avoid classic DNA extraction and to reduce total experiment time to approximately 2 hours. The objective was to design strain-specific tools able to confirm and quantify the presence of different strains in any microalgae culture so as to achieve maximal productivity and quality of the produced biomass.