Cell Disruption and Pressurized Liquid Extraction of Carotenoids from Microalgae

Josef Taucher,Sascha Baer

doi:10.4172/2157-7544.1000158

Josef Taucher, Sascha Baer

Open Access

https://doi.org/10.4172/2157-7544.1000158

Copy DOI

Abstract

Microalgae are very promising organisms for the production of high-value compounds such as carotenoids. Nevertheless, their commercial use is so far hampered by the lack of efficient processes and currently feasible for very few strains. One of the most relevant factors is the high effort for downstream processing, e.g., cell disruption and extraction. Thus, the presented studies were dedicated to investigate and optimize these two steps for carotenoid production with microalgae. Six different cell disruption techniques (high pressure homogenizer, ball mill, Ultra Turrax, repeated freeze and thaw, freeze-drying, ultra-sonication) were compared in lab scale for three species: Haemotococcus pluvialis, Chromochloris zofingiensis and Chlorella sorokiniana. The carotenoid recovery was determined via HPLC-UV/Vis after pressurized solvent extraction. Furthermore, factors influencing the applied extraction methods such as solvent, temperature, duration and number of cycles were optimized in order to reach highest recovery rates. While rough mechanical methods such as ball mill and high pressure homogenizer showed the highest effectivity for cell disruption of all three investigated strains, the influence of non-mechanical methods - i.e., repeated freeze and thaw cycles - on the efficiency of the extraction of astaxanthin, lutein and β carotene increased reversely proportional to cell size and cell wall rigidity. For H. pluvialis repeated freezing and thawing resulted in a factor 240 times lower extraction yield compared to high pressure homogenizer, while both methods were comparable for C. sorokiniana. From six tested solvents, dichloromethane resulted in the highest carotene recovery yield, three times higher in comparison to n-hexane. Variation of the extraction temperature from room temperature to 120°C showed an optimum at 60°C. Nearly complete extraction was reached after one cycle of 10 minutes. The data presented here demonstrate the necessity of lab scale optimization of cell disruption and extraction process for future upscaling

Highlights

Microalgae, including cyanobacteria, play an increasing role in science and industry, due to their wide range of commercial and potential novel products [1,2,3]
The highest disruption yield - around 80% - of the thick encysted cell walls was reached by using mechanical methods such as ball mill, Ultra Turrax and high pressure homogenizer, while other mechanical and non-mechanical methods, such as repeated freeze and thaw cycles resulted in disruption yields of ≤ 10%
The highest carotenoid extraction yield was measured after disruption with the high pressure homogenizer (4.21 μg total carotenoid·mg-1 dry weight (d.w.), taken as 1 for normalization purpose), ball mill (3.56 μg total carotenoid·mg-1 d.w.) and Ultra Turrax (3.42 μg total carotenoid·mg-1 d.w.)

Summary

Introduction

Microalgae, including cyanobacteria, play an increasing role in science and industry, due to their wide range of commercial and potential novel products [1,2,3]. Carotenoids are a group of structurally highly diverse terpenoid pigments (more than 750 have been isolated), which can be divided into carotenes and oxygenated derivatives of carotenes, so called xanthophylls [10,11,12]. They act as light-harvesting pigments, absorb light in a range of λ=400-550 nm and transfer the light to chlorophyll [12,13]. Market prices vary from 300 3,000 US$∙kg-1 and 2,500-10,000 US$∙kg-1 in case of β-carotene and astaxanthin, respectively [16,17]

Methods

Results

Conclusion