Neutral sugars determination in Chlorella: Use of a one-step dilute sulfuric acid hydrolysis with reduced sample size followed by HPAEC analysis

• Published in: Algal research (Amsterdam) 2017-06, Vol.24, p.130-137
• Main Authors: Souza, Marcella Fernandes de, Pereira, Daniel Santos, Freitas, Suely Pereira, Bon, Elba Pinto da Silva, Rodrigues, Marcoaurélio Almenara
• Format: Article
• Language: English
• Subjects: Carbohydrate analysis; Chlorella sugar composition; Dilute sulfuric acid hydrolysis; HPAEC-PAD
• ISSN: 2211-9264; 2211-9264
• DOI: 10.1016/j.algal.2017.03.019

The accurate determination of the chemical composition of microalgae is essential when evaluating their potential as feedstock for the production of biofuels and biochemicals. The usual methodology for the determination of total microalgal carbohydrate content combines a two-step acid hydrolysis of the microalgal biomass with an analysis of the released monosaccharides using phenol-sulfuric acid, but the latter is a hazardous procedure. Alternatively, the sugar monomers that are present in the acid hydrolysate can be identified using high performance liquid chromatography (HPLC), whose accuracy may be compromised by compounds derived from the complex cell composition of the microalgae. Aiming to further the extant analytical procedures for determination of the neutral sugar content in microalgae of the Chlorella genus, the present study evaluated a one-step dilute sulfuric acid hydrolysis followed by the analysis of the released monosaccharides using high performance anion exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). The proposed HPAEC-PAD method proved to be specific, sensitive, accurate, precise and robust. The one-step dilute sulfuric acid hydrolysis process showed an acceptable correlation with the widely used two-step technique for the determination of total neutral sugars in Chlorella, despite the use of a sixfold smaller sample size. The method was also successfully applied to Mychonastes homosphaera, another green microalga of the phylum Chlorophyta, indicating its applicability for broader use beyond the Chlorella genus. Furthermore, the combination of both methods is proposed as a useful tool to evaluate recalcitrant glucose moieties in microalgal biomass. [Display omitted] •HPAEC-PAD was validated for the analysis of Chlorella carbohydrates.•The one-step acid hydrolysis was efficient for profiling Chlorella neutral sugars.•The one-step hydrolysis used a sixfold smaller sample than the two-step hydrolysis.•Structural polysaccharides, like cellulose, were not hydrolyzed by this method.•Chlorella cellulose content is discussed vis-à-vis the current analytical procedures.