Assessment of Phycocyanin Extraction from Cyanidium caldarium by Spark Discharges, Compared to Freeze-Thaw Cycles, Sonication, and Pulsed Electric Fields.

Marie-Christine Sommer,Martina Balazinski,Katja Zocher,Raphael Rataj,Juergen F Kolb,Sebastian Wenske

doi:10.3390/microorganisms9071452

Marie-Christine Sommer, Martina Balazinski + Show 4 more

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https://doi.org/10.3390/microorganisms9071452

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Abstract

Phycocyanin is a blue colored pigment, synthesized by several species of cyanobacteria and red algae. Besides the application as a food-colorant, the pigmented protein is of high interest as a pharmaceutically and nutritionally valuable compound. Since cyanobacteria-derived phycocyanin is thermolabile, red algae that are adapted to high temperatures are an interesting source for phycocyanin extraction. Still, the extraction of high quality phycocyanin from red algae is challenging due to the strong and rigid cell wall. Since standard techniques show low yields, alternative methods are needed. Recently, spark discharges have been shown to gently disintegrate microalgae and thereby enable the efficient extraction of susceptible proteins. In this study, the applicability of spark discharges for phycocyanin extraction from the red alga Cyanidium caldarium was investigated. The efficiency of 30 min spark discharges was compared with standard treatment protocols, such as three times repeated freeze-thaw cycles, sonication, and pulsed electric fields. Input energy for all physical methods were kept constant at 11,880 J to ensure comparability. The obtained extracts were evaluated by photometric and fluorescent spectroscopy. Highest extraction yields were achieved with sonication (53 mg/g dry weight (dw)) and disintegration by spark discharges (4 mg/g dw) while neither freeze-thawing nor pulsed electric field disintegration proved effective. The protein analysis via LC-MS of the former two extracts revealed a comparable composition of phycobiliproteins. Despite the lower total concentration of phycocyanin after application of spark discharges, the purity in the raw extract was higher in comparison to the extract attained by sonication.

Highlights

The bright blue colour of the pigment phycocyanin is of great interest as a natural colorant in food industry
Phycobiliprotein extractability of Cyanidium caldarium with standard extraction methods and spark discharges was determined by absorption and fluorescence spectroscopy with respect to phycocyanin, allophycocyanin and phycoerythrin content released to the supernatant
Disintegration by spark discharges, as well as disintegration by sonication facilitated the extraction of phycocyanin from the red algae Cyanidium caldarium

Summary

Introduction

The bright blue colour of the pigment phycocyanin is of great interest as a natural colorant in food industry. Its good water solubility especially allows for the processing of extracted phycocyanin as a food colorant for ice cream, jelly or chewing gum [1]. Beyond the safe application of naturally derived phycocyanin as a food colorant, the pigment has been shown to have beneficial effects on health [4]. Phycocyanin acts as an anti-inflammatory agent and an antioxidant [5,6], and is considered a potential drug for cancer treatment [7]. Most commonly, cyanobacteria such as Arthrospira sp. The outstanding preference of Cyanidium caldarium to live in extreme habitats such as hot, acidic springs [9]

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