Starch determination in Chlorella vulgaris-a comparison between acid and enzymatic methods

Different methods for estimating starch in Chlorella vulgaris were compared with the view of establishing a procedure suitable for rapid and accurate determination of starch content in this microalgal species. A close agreement was observed between methods that use perchloric acid and enzymatic methods that use α-amylase and amyloglucosidase to hydrolyze the starch of microalgae grown under different nitrogen culture conditions. Starch values obtained by these methods were significantly higher than those estimated by using hydrochloric acid as solubilizing and hydrolyzing agent. The enzymatic method (EM1) proved to be the most rapid and precise method for microalgal starch quantification. Furthermore, the evaluation of resistant starch by enzymatic methods assayed in nitrogen-sufficient and nitrogen-starved cells showed that no formation of this type of starch occurred in microalgae, meaning that this should not interfere with starch content determinations.This research work was supported by the grants SFRH/BD/44724/2008 (Bruno Fernandes) from Fundacao para a Ciencia e a Tecnologia (Portugal) and SFRH/BPD/44935/2008 (Giuliano Dragone). The authors also acknowledge the financial support received through the projects INNOVALGAE (FCT PTDC/AAC-AMB/108511/2008) and ALGANOL