Pilot scale production, extraction and purification of a thermostable phycocyanin from Synechocystis sp. PCC 6803

Anton Puzorjov,Suleyman Mert Unal,Martin A Wear,Alistair J Mccormick

doi:10.1016/j.biortech.2021.126459

Anton Puzorjov, Suleyman Mert Unal + Show 2 more

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https://doi.org/10.1016/j.biortech.2021.126459

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Journal: Biomass	Publication Date: Dec 1, 2021
Citations: 9	License type: cc-by

Affiliation: University of Edinburgh

Abstract

Phycocyanin (PC) is a soluble blue pigment-protein primarily harvested from the cyanobacterium Arthrospira platensis. PC is in high demand from several industries, but its narrow stability range limits potential applications. Here, a pilot scale (120 L total) batch production, extraction and purification process for thermostable PC (Te-PC) from a Synechocystis sp. PCC 6803 'Olive' strain expressing the PC operon cpcBACD from Thermosynechococcus elongatus BP-1 on a self-replicating vector is presented. Batch cultivation without antibiotics had no impact on growth or Te-PC production and optimisation of growth conditions resulted in Te-PC contents of 75.3 ± 1.7 mg g DW−1. Wet biomass was harvested following chitosan-based flocculation with a 97 ± 2% efficiency, and Te-PC was extracted by high pressure homogenisation. Subsequent purification by heat-treatment and two-step ammonium sulfate precipitation removed chlorophyll and allophycocyanin contamination, resulting in Te-PC purities of 2.9 ± 0.7 and a mean Te-PC recovery of 84 ± 12%.

Highlights

Phycocyanin (PC) is a soluble, pigment-protein found within the light-harvesting phycobilisome complex of cyanobacteria and red algae
PC from the thermophilic cyanobacterial species Synechococcus lividus PCC 6715, Thermosynechococcus elongates BP-1 and Synechococcus lividus SyI is stable at 60 ◦C, 70 ◦C and 80 ◦C, respectively (Puzorjov et al, 2021), while PC extracted from the red alga Galdieria phlegrea retains its fluorescent properties up to 85 ◦C (Ferraro et al, 2020)
TeBACD cultures were grown in 1xBG11 medium under white light (150 μmol photons m− 2 s− 1) in the presence or absence of kanamycin to assess the impact of the antibiotic on cyanobacterial growth and thermostable PC (Te-PC) production

Summary

Introduction

Phycocyanin (PC) is a soluble, pigment-protein found within the light-harvesting phycobilisome complex of cyanobacteria and red algae. Purified PC is characterised by a bright blue colour and red fluorescence, and is primarily harvested from the filamentous cyanobacterium Arthrospira platensis (Spirulina). PC extracted from A. platensis denatures at temperatures exceeding 45 ◦C and/or outside a pH range of 4–7, which results in a loss of its blue colour, fluorescence and anti-oxidant properties (Pan-utai et al, 2018). PC from the thermophilic cyanobacterial species Synechococcus lividus PCC 6715, Thermosynechococcus elongates BP-1 and Synechococcus lividus SyI is stable at 60 ◦C, 70 ◦C and 80 ◦C, respectively (Puzorjov et al, 2021), while PC extracted from the red alga Galdieria phlegrea retains its fluorescent properties up to 85 ◦C (Ferraro et al, 2020). Cultivation of extremophiles at the higher temperatures needed for optimal growth requires a substantial energy investment (Puzorjov et al, 2021)

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