Optimization of biomolecule extraction from Spirulina platensis with [bmim][Cl]

Abstract

Spirulina platensis stands out as a promising raw material for various industries due to its composition, rich in proteins and carbohydrates, and its valuable phycobiliprotein content. This study explored the influence of four key factors – incubation time, incubation temperature, ultrasound exposure, and IL mass fraction – on the single-step extraction of these cyanobacterial ingredients using [bmim][Cl]. Results were analysed through a four-factor surface response analysis, allowing the identification of the most relevant operational factors for the extraction of each biomolecule.

The IL mass fraction in its linear and quadratic form emerged as the primary factor influencing protein and phycobiliprotein recoveries, although other factors such as the interaction between incubation time and incubation temperature were also deemed significant. In these experiments, protein recovery ranged over a wide yet low range, going from 2.37 to 24.30 %, while phycobiliprotein recovery did not reach 10 % for any of the three studied pigments. In contrast, carbohydrate recovery was higher. It ranged between 35.85 and 63.25 %, and was only influenced by the linear term for the incubation temperature.

The excellent fit of the protein recovery model and its pronounced ascending trend with increasing IL mass fractions prompted further experimental work into the influence of this factor. These additional experiments, focusing solely on the IL mass fraction, confirmed the observations derived from the surface response analysis, with IL mass fractions outside the studied range following the observed ascending trend. Such post-model experiments led to higher recoveries even when operating at low IL mass fractions due to the suppression of negatively-influencing factors, leading to single-step protein recoveries ranging between 15.92 and 28.95 %.

The purity of the obtained extracts from both model and post-model experiment was also evaluated. Purity in model experiments was driven by practically the same factors influencing biomolecule recovery, while post-model experiments revealed how the change of the operational conditions not only increased protein recovery, but also boosted its purity.