A simple and efficient strategy for fucoxanthin extraction from the microalga Phaeodactylum tricornutum
Graphical abstract
Introduction
Marine diatoms have a siliceous skeleton and are found in the upper waters of the world ocean [1]. Significant progress has been made in the development of Phaeodactylum tricornutum for a rich source of fucoxanthin over the past two decades. The whole genome of P. tricornutum has been sequenced and functionally identified in recent years [2], [3], [4]. Moreover, fucoxanthin production of P. tricornutum culture under light and agitation conditions has been investigated [5]. In outdoor microalgal mass culture systems, P. tricornutum is rather tolerant to high pH and can grow under low light intensity [1], [6]. Several procedures developed for fucoxanthin extraction from P. tricornutum have been evaluated and optimized [7]. In general, P. tricornutum has been used as a potential feedstock for fucoxanthin production and an ideal species in the microalgal industry due to its high photosynthetic efficiency, vigorous growth, as well as being a rich source of fucoxanthin [8].
As one of the most abundant marine carotenoids derived from microalgae [9], the global market demand for fucoxanthin production in increasing [10], [11]. Fucoxanthin is not only responsible for capturing solar energy to carry out photosynthesis [12] but also has become widely recognized as a bioactive compound of great importance for human health [13]. Moreover, fucoxanthin has been proved to be safe for consumption by humans or animals. Functional healthy food supplemented with fucoxanthin has been proven safe for human consumption [10].
The methods to prepare high-quality fucoxanthin have attracted much attention from researchers worldwide because of its broad application prospects. Fucoxanthin has a unique structure consisting of an allenic bond, a 5, 6-monoepoxide, and a conjugated carbonyl group in the polyene chain of the molecule [14]. However, fucoxanthin can be easily isomerized and even degraded by heating, aerobic exposure, and illumination during the process of extraction, purification, and storage, which is attributed to the functional groups of fucoxanthin [15]. Presently, fucoxanthin may be chemically produced [16], while most commercially available fucoxanthin is extracted from diverse brown seaweeds due to their relatively low cost [11]. Compared with the brown seaweeds, the content of fucoxanthin in marine microalgae is 5 to 10 times higher, and marine microalgae have great potential as a promising source of fucoxanthin for commercial applications [17]. Lipids and fucoxanthin are successfully co-extracted from microalga P. tricornutum by ethanol extraction. Then, a biphasic partitioning system consisting of n-hexane/ethanol/water 20:60:40 (v/v/v) has been investigated for the recovery of lipids and the preliminary separation of fucoxanthin [7], [18]. The purification of fucoxanthin has been mainly accomplished using several chromatographic technologies, including silica gel column chromatography [19], centrifugal partition chromatography [20], thin-layer chromatography [21], and preparative high-performance liquid chromatography [19]. However, two disadvantages are associated with the fucoxanthin prepared by the above-mentioned methods. Most importantly, the above-mentioned approaches for the preparation of high-purity fucoxanthin require harmful organic solvents, which cannot meet the consumers' needs and the environmental requirements. In addition, the commercial purification of fucoxanthin by these methods is costly, and supplies can be limited. Therefore, the development of the preparation strategy for high-quality and industrial-scale fucoxanthin via eco-friendly routes is a major research challenge for the food industry and nutrition fields.
Currently, ethanol extraction has been widely used for the preparation of traditional Chinese medicine (TCM). For example, flavonoids are successfully extracted from the leaf of Ginkgo biloba using the ethanol extraction method [22]. As a common purification method, ethanol precipitation has been extensively used in the purification of many compounds [23], [24]. Interestingly, as environmentally sustainable production processes, both ethanol extraction and ethanol precipitation possess several distinct advantages, including simple operation, ease of scaling-up, solvent safety, and green products [25]. To produce high-quality fucoxanthin for the food industry and nutrition fields, we proposed a novel and industry-oriented method to obtain high-purity fucoxanthin from the marine diatom P. tricornutum. This approach was composed of three steps, including algal culture, ethanol extraction, and ethanol precipitation. The high-quality fucoxanthin produced via the above-mentioned eco-friendly routes demonstrated a great application potential in meeting the ever-increasingly high-quality fucoxanthin demands for food and nutrition fields.
Section snippets
Microalgal culture
The marine diatom P. tricornutum used in this study was provided by the Microalgae Collection at Ningbo University. The microalgal cultivation was carried out in 30-L plastic cylinders at 20 °C, and the air was continuously supplied at 5 L/min by air-lift. The light was provided by 60-W fluorescent lamps at an intensity of 3000 lx. The microalga was cultured in an F/2 medium prepared from filter-sterilized seawater. All cultures were harvested after 11 days of cultivation in the late
Fucoxanthin content in the lyophilized microalgal powder
In this study, fucoxanthin has been quantified in the lyophilized microalgal powder by the analytical HPLC. Briefly, the methanol extracts of P. tricornutum were analyzed by HPLC to detect the fucoxanthin content. The results showed that the fucoxanthin content in dry weight sample was 8.92 ± 0.31 mg/g. The results demonstrated that P. tricornutum contained more fucoxanthin than brown seaweeds previously evaluated [17]. Clearly, the diatom P. tricornutum had more potential as source of
Conclusions
This study provided an innovative fucoxanthin extraction strategy for the fucoxanthin preparation from the microalga P. tricornutum. This approach was composed of three steps, including algal culture, ethanol extraction, and ethanol precipitation. The optimum organic solvent extraction conditions of fucoxanthin were as follows: solvent-to-solid ratio of 40 mL/g, 70% ethanol, extraction duration of 90 min, extraction temperature of 25 °C, and extraction of one time, while fucoxanthin extraction
Statement of informed consent, human/animal rights
No conflicts, informed consent, or human or animal rights are applicable to this study.
CRediT authorship contribution statement
Jingwen Sun: Conceptualization, Methodology, Formal analysis, Investigation, Writing – original draft, Writing – review & editing. Chengxu Zhou: Conceptualization, Methodology, Resources, Writing – review & editing. Pengfei Cheng: Conceptualization, Methodology, Resources, Writing – review & editing. Junwang Zhu: Formal analysis, Investigation, Writing – review & editing. Yuqin Hou: Formal analysis, Investigation, Writing – review & editing. Yanrong Li: Conceptualization, Methodology,
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work was financially supported by the National Key Research and Development Program of China (2018YFA0903003, 2018YFD0901504, 2018YFC0310901), the Science and Technology Program of Zhejiang Province (LGG22D060001), Ningbo Public Service Platform for High-Value Utilization of Marine Biological Resources (NBHY-2017-P2), the National Natural Science Foundation of China (41406163), the LiDakSum Marine Biopharmaceutical Development Fund, and the National 111 Project of China.
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