Abstract
Microalgae, historically relevant to aquaculture sector, can effectively
contribute to the sustainability in several production chain. The
physical and chemical environmental factors play a direct or indirect
role in shaping the composition of their intracellular compounds of
these organisms. Among these compounds, fatty acids are particularly
noteworthy, with various species harboring an extensive array of them.
Notably, the marine dinoflagellate Prorocentrum micans excels in
the production of essential polyunsaturated fatty acids (PUFA),
including DHA and EPA. The objective was to determine which factors
contribute to the accumulation of the PUFA in a P. micans strain.
A factorial design of 3x3 composed by the following factors:
illumination (5, 12.5, 20 µmol photons m-2s-1), nitrate dose (0, 75, 150 mg
ml-1) and inoculum volume (50, 125, 200 ml) was
examined to determine the better growth conditions for P. micans .
Furthermore, lipid profile and the fatty acids profile were analyzed at
the end of the cultivation. The results determined that, maximum
averages of DHA (20%) and EPA (1%), in the biomass, were registered in
cultures without nitrate, low irradiance (5 µmol photons
m-2 s-1) and high volume of inoculum
(200 ml). The maximum cell concentration recorded was
3.1×104 cells ml-1, at the end of
the culture. So, it can be concluded that the evaluated strain is easily
adapted to the culture flow and, the culture conditions to which it was
subjected allows its biomass to be considered an interesting alternative
as lipid input in aquaculture activity.
Keyword : P. micans DHA, EPA, nitrate
Introduction
Due to the global changes that humanity faces to maintain, protect and
improve food security, aquaculture has several challenges to overcome,
mainly sustainability, biosecurity, regulatory structures in accordance
with ocean ecosystems and food supplies, since these charge greater
relevance due to the nutritional level they perform, especially as
unique and extremely diverse providers of omega-3 fatty acids and
essential bioavailable micronutrients (MUSTAFA and SHAPAWI, 2015; FAO
2022). In the aquatic environment, microalgae are the base of the
trophic chain, capable of accumulating a series of active compounds,
among which fatty acids stand out, especially polyunsaturated fatty
acids (PUFAs). important for the development and reproduction of
zooplankton organisms, seeds and other secondary consumers in their
initial levels of development (IKAWA, 2004; HERNÁNDEZ, 2016; GONÇALVEZ
et al., 2017; REMMENS et al., 2018; PELTOMA et al., 2019; OLIVEIRA et
al., 2022).
The importance of microalgae in the diet of the larval stages of various
aquatic organisms is mainly due to the presence of polyunsaturated fatty
acids such as; C22:6n‐3 docosahexaenoic acid (DHA) and C20:5n‐3
eicosapentaenoic acid (EPA) that are synthesized and transferred through
the food chain ingested by secondary consumers, as they play a crucial
role in development neural, tissue formation, physiological functions,
cell walls and energy storage of the latter, it is due to this, that
various studies refer to a connection between the nutritional value of
microalgae and their lipid profile (ADAME et al., 2012; GONÇALVEZ et
al., 2017; RAJA et al., 2018; PELTOMA et al., 2019).
With the development of the aquaculture industry and the demand that
this implies, in terms of quality and quantity of organisms produced in
closed or open spaces, inputs rich in lipid compounds are increasingly
scarce or are replaced by alternative products that lack the necessary
nutrients for a balanced feed of aquatic organisms (PELTOMA et al.,
2019). In this context and given that microalgae contain interesting
lipid profiles, they are positioned as a potential resource so that,
through mass cultivation processes, biomass or extracts can be obtained,
as raw material or biochemically adequate input for feeding cultivable
organisms, also considering that microalgal productivity does not
interfere with food safety and favors the environment (ATKINSON, 2013;
FU et al., 2017; LORENZEN et al., 2017; REMMENS et al., 2018; PELTOMA,
2019).
The microalgae with considerable lipid profiles are those of the group
of diatoms and dinoflagellates, the first of which is characterized by
accumulating EPA and the second DHA in a greater proportion compared to
other fatty acids (SEXTON and LOMAS 2018; ZULU et al., 2018; PELTOMA et
al., 2019), both groups are widely distributed in the aquatic
environment and even when some of them face certain factors such as;
temperature, irradiance, salinity tend to proliferate forming algal
blooms, only dinoflagellates can adapt very well due to their
mixotrophic or heterotrophic condition to sudden changes, losing their
inhibitory capacity on the development of other organisms (LEE et al.,
2017; ABD et al. ., 2022).
Within the group of dinoflagellates, Prorocentrum micansturns out to adapt quite easily to culture conditions, it stands out for
its high content of DHA over other lipid components, which makes it a
potential resource whose biomass would be an interesting input or raw
material in the production of aquaculture products (KATTNER and
BROCKMANN, 1978; SUH et al., 2015; HERNÁNDEZ et al., 2019).
In culture, P. micans is a species whose growth is mainly
impacted by thermal and light variation, as well as by nutrient levels,
especially nitrates (LEE et al., 2017; REMMENS et al., 2018). The
variations of these factors determine the lipid profile of the species;
among the fatty acids that can be recorded and are related to algal
bloom events are considered; octadecapentaenoic acid C18:5n3 (OPA) and
octadecatetraenoic acid C18:4n3 (ODTA), the latter quite toxic (IKAWA,
2004).
Therefore, to explore and evaluate the factors that contribute to the
accumulation of fatty acids of interest in the aquaculture industry inP. micans and minimize or inhibit toxic substances, light
intensity and nitrate content should be taken into account, given which
are critical factors that affect the photosynthesis of these algal
organisms, also considering that the toxic activity of PUFAs may be
related to photooxidation (IKAWA, 2004; LEE et al., 2017; REMMENS et
al., 2018).
In this sense, the objective of the present study was to evaluate the
culture conditions in a controlled environment that contribute to the
accumulation of fatty acids with emphasis on DHA and EPA in the marine
dinoflagellate P. micans strain IMP-BG-036, with the purpose of
that is considered a potential input for the preparation of enrichments
or other products that are required in the aquaculture activity. It is
necessary to mention that the afore mentioned strain was evaluated and
selected from a set of strains of the same species isolated from
different places on the Peruvian coast and was the one that best adapted
to the culture flow with high levels of various fatty acids, among which
stand out the DHA.
Material and methods