AOP Journal of Environmental
Waste Management
http://dx.doi.org/10.14437/AOPJEWM-1-101
Review
Received: Nov 24, 2015
Accepted: Dec 02, 2015
Published: Dec 05, 2015
Dolores Hidalgo, AOP J Environ Waste Management 2015, 1:1
Heterotrophic Microalgae Cultivation to Synergize Anaerobic Digestate Treatment with
Slow-Release Fertilizers and Biostimulants Production
Dolores Hidalgo1,2*
1
CARTIF Technology Centre, 47151 Boecillo, Valladolid, Spain
2
ITAP Institute, University of Valladolid, 47011 Valladolid, Spain
Abstract
Keywords: Anaerobic Digestate; Biostimulants; Fertilizers;
Microalgae are a highly diverse and specialized group of
Heterotrophic Growth; Microalgae; Manure
microorganisms. The flexibility to switch their nutritional mode
*
based on substrate availability and light condition is one of their
Boecillo, 205. 47151 Boecillo, Valladolid, Spain; Tel: +34 983
multiple advantages. This paper analyze the current state of a
546504; Fax: +34 983 546521; E-mail: [email protected]
specific niche of microalgae growth: heterotrophic cultivation,
Introduction
Corresponding Author: Dolores Hidalgo, Parque Tecnológico de
specifically supported by anaerobic digestate as carbon and
The term “microalgae” traditionally refers to eukaryotic or
nutrients source, replacing in this way the traditional support of
prokaryotic photosynthetic microorganisms that can grow rapidly
light
cultivation,
and live in harsh conditions due to their unicellular or simple multi
heterotrophic systems are more suitable for producing high cell
cellular structure [1]. Nowadays, strictly speaking, the term
densities of microalgae which can be converted into valuable
excludes cyanobacteria and prokaryotic microorganisms in general,
products. Apart from that, heterotrophic cultivation is far simpler to
although most of the references found in bibliography still maintain
construct facilities, cheaper to operate and easier to maintain on a
the traditional definition.
energy.
When
compared
to
autotrophic
large scale than autotrophic cultivation. This capacity allows large
Microalgae are present in all existing earth ecosystems
volume applications, as organic waste streams treatment combined,
representing a big variety of species living in a wide range of
or separated, with production of slow release fertilizers and
environmental conditions. An in depth description of microalgae is
biostimulants. Recycling the nutrients from anaerobic digestion an
presented by Richmond and Ho [2]. These authors estimates that
assimilating them into algal biomass can result in high quality
more than 50,000 species exist, but only a limited number, of
fertilizers without incurring the environmental and monetary costs
around 30,000, have been studied and analyzed, so their potential
of using chemical fertilizers while simultaneously remediating the
still awaits exploitation in the biotechnological sector.
waste effluent from this process. Manure digestate is an especially
attractive
feedstock
to
grow
microalgae
for
Today micro algal production is a burning issue given the
biofertilizers
wide variety of practical and potential metabolic products that can
production, as it is less contaminated than untreated effluents and
be obtained, such as food supplements, fertilizers, biostimulants,
rich in nitrogen and phosphorus. The application of biofertilizers
soil amendments, lipids, enzymes, biomass, polymers, toxins,
has been shown to decrease soil erosion, pest infestation, and water
pigments, tertiary wastewater treatment, and “green energy”
requirements, and improve soil tilth. The use of algae as
products. Also a growing market for algae products exists [3]
biofertilizers of biostimulants is particularly appealing. In this
turning the interest in microalgae from scientific to economic.
paper the challenges faced during heterotrophic microalgae large
The most common procedure for microalgae cultivation is
scale production and limiting factors which hinder the microalgae
autotrophic growth [4]. In this case, photosynthetic microalgae are
growth are enumerated. A general perspective of the field is
cultivated in naturally or artificially illuminated environments.
presented, describing the best-known examples from the literature
Under autotrophic cultivation, the cells harvest light energy and use
and analyzing the prospect of heterotrophic cultures to produce
CO2 as a carbon source. The limiting factor of the cultivation in this
sustainable fertilizers and biostimulants.
Copyright: © 2015 AOPJEWM. This is an open-access article distributed under the terms of the Creative Commons Attribution License, Version 3.0, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author and source are credited.
Volume 1 • Issue 1 • 101
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Citation: Dolores Hidalgo (2015), Heterotrophic Microalgae Cultivation to Synergize Anaerobic Digestate Treatment with Slow-Release
Fertilizers and Biostimulants Production. AOP J Environ Waste Management 1:101
http://dx.doi.org/10.14437/AOPJEWM-1-101
Page 2 of 12
case is the introduction of enough natural or artificial light to allow
massive growth and dense populations [5].
This paper focuses its attention on heterotrophic
cultivation of microalgae and how they can be used for
As practiced with other microbial communities producing
biofertilizers and biostimulants production. Questions associated
economic products, open ponds that try to imitate natural
with production and processing of microalgae are considered, not
microalgae environments are the most common option for mass
only those directly related with biofertilizers production but also
cultivation
[6,
7].
However
these
systems
face
several
the possibilities of combining it with pollution control, in particular
disadvantages as: poor light diffusion inside the pond;
mono-
with waste effluents treatment, especially anaerobic digestate.
cultivation is difficult to maintain because of constant airborne
Heterotrophic Cultivation of Microalgae
contamination; uncontrollable local weather conditions make
During microalgae respiration, oxygen is consumed and
microalgae production seasonal; harvesting is laborious and costly
CO2 produced. The respiration rate is intrinsically related to growth
and; continuous and clean water is needed [4].
and cell division. In microalgae, dark respiration of an organic
To overcome disadvantages of open ponds numerous
substrate assimilated from the medium has rates varying from 0.01
photo-bioreactors prototypes have been designed [8-13], but these
to 0.6 d-1 [4]. This dark respiration plays two important roles in
systems
them
microalgae development: (a) it serves as the exclusive source of
uneconomical, especially for low-cost end products. Among other
energy for maintenance and biosynthesis under light absence
inconveniences, as the requirement of high initial investment and
conditions, and (b) it provides carbon skeletons for biosynthesis.
continuous maintenance [14], it is pointed out that photo-
During heterotrophic growth conditions biomass synthesis can
bioreactors of high volume do not achieve an efficient light
proceed at nearly the maximal theoretical efficiency [19].
dispersion during operation, due to the densification of the media
According to Chen and Chen [20], the main key issues to be
when the microalgae grow [15] or due to the formation of algal bio
considered in large-scale heterotrophic cultures of microalgae are:
film on bio-reactor surfaces [9]. In both cases, light penetration into
(a) good survival of the selected strain during cultivation, (b) low
the culture is limited.
cultivation costs, reflected as the ability of the strain to efficiently
have
their
own
shortcomings
that
make
A feasible alternative for microalgae cultivation (although
use inexpensive carbon sources (as those contained in residual
restricted to some micro algal species) is heterotrophic growth in
effluents),
tolerate
the absence of light. In this case, the photosynthetic process gets
economical worth (sub products), and (c) the strains must also be
suppressed and microalgae gain energy from alternative organic
easy to handle and robust (its cell walls must withstand
processes converting sugar into lipids [16]. Since light does not
hydrodynamic
need to penetrate the microalgae mass, irradiation is not now a
bioreactors).
and
environmental
mechanical
changes,
shear
and
occurring
generate
in
large
limiting factor, and the growth of the microalgae can be
Oxygen is a key factor in heterotrophic cultivation.
significantly more intense, allowing for greater operation yields.
Growth rates are enhanced by higher levels of aeration. The
Furthermore, microalgae through heterotrophic nutritional mode
limitation of oxygen in a microalgae heterotrophic culture may
facilitate high biomass productivities which provide an economic
reduce the specific growth rate and lower the productivity of
feasibility for large scale production [17, 18].
biomass when cell density is high [21- 23].
The main attractions of the heterotrophic growth approach
The ability of a number of micro algal species to grow
are cost effectiveness, relative simplicity in operations and easy
with organic carbon substrates in the presence of light has been
maintenance. This modality allows the use of practically any
broadly studied [24- 26] but it not easy to predict which specific
fermentor as a bioreactor [4]. Growth of heterotrophic algae
substrates can be used or preferred by any given microalgae [21].
remains constant as carbon and nutrients are available but
On the contrary, the number of current commercially
productive growth of autotrophic microalgae increases in day light
microalgae that are capable of growth on organic carbon substrates
and decreases at night [18].
in the dark, and where experience of fed batch cultivation has been
gained, is very limited [23]. Fortunately, some of the most common
Volume 1 • Issue 1 • 101
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Citation: Dolores Hidalgo (2015), Heterotrophic Microalgae Cultivation to Synergize Anaerobic Digestate Treatment with Slow-Release
Fertilizers and Biostimulants Production. AOP J Environ Waste Management 1:101
http://dx.doi.org/10.14437/AOPJEWM-1-101
Page 3 of 12
and best-studies microalgae, such as Chlorella [27, 28],
wastewaters kept in the dark and in oxidation ponds [17] found that
Scenedesmus [29, 30] or Muriellopsis [31, 32] are also
adding several carbon sources to municipal wastewater that
heterotrophs.
normally do not support micro algal growth allowed heterotrophic
Microalgae heterotrophic cultivation without light and
growth of Chlorella vulgaris. Table 2 shows some studies
with the controlled addition of an organic source of carbon,
conducted on wastewater treatment with microalgae.
nutrients and energy is similar to procedures established with
Table 2. Examples of wastewater treatment with algae in
bacteria in multipurpose stirred closed tanks. In order to be able to
heterotrophic mode (adapted from Mohan et al. [18]).
cultivate heterotrophic microalgae at large-scale in conventional
While several carbon sources were proposed for
stirred bioreactors, a micro algal species should meet a number of
heterotrophic growth of microalgae (such as sucrose, lactate,
criteria, starting by its resistance to mechanical stress and the
lactose, ethanol), practical evaluation of these sources shows that
ability to grow in an inexpensive medium. These criteria were
only a few substrates are supported by solid evidence. Those
gathered by Bumbak et al. [23] and included 1) the availability of
include glucose, glycerol, and acetate. None of the other carbon
the species as axenic culture, 2) a reasonable specific grow rate, 3)
sources tested supported sufficient growth [4].
temperature achievable with conventional cooling (25-40ºC) and,
4) micro alga robustness and resistance.
Table 1 summarizes the characteristics of some microalgae
species growing in controlled heterotrophic environments. The
Of special interest are those wastewater streams than
contain the assimilated low molecular substrates that microalgae
can use and can be mixed with water to create a substrate for
microalgae, as for example, anaerobic digestates.
different genera show a wide rate of growth rates depending on the
Anaerobic digestate is a very abundant effluent. The use of
species and assay conditions, such as temperature, pH or dissolved
anaerobic digestion has been spread in Europe, thanks to the
oxygen levels. Table 1: Growth characteristics of microalgae in
support of specific legislative tools aimed at increasing the
heterotrophic batch cultures (adapted from Bumbak et al. [23]).
production of biogas in different economic sectors [39]. But the
Fed batch cultivation is the most effective technique for
anaerobic digestion process does not significantly reduce the
reaching high biomass concentrations in a short time and controlled
amount of nutrients in the digestate, in fact, it favors the presence in
manner in cultures grown heterotrophically [22]. This is commonly
these streams of more bioavailable nitrogen forms such as
achieved through controlling the rate of addition of the organic
ammonium, and organic phosphorus is partly released from the
carbon and energy source (i.e. the substrate feed), that helps to
organic
avoid inhibitory effects due to high substrate concentrations [33].
phosphorus [40]. As a result of the digestion process, it might be
Varying feed strategies can lead to different efficiencies of biomass
anticipated that the proportion of readily available nutrients
and/or product formation.
increases. On the other hand, the methanogenic process keeps in the
Algal Based Digestate Treatment Systems
digestate also a remaining fraction (highly significant in some
fraction
and
becomes
available
as
water-soluble
Waste effluents treatment is a technically feasible
cases) of semi-transformed organic carbon. The presence of
application of autotrophically grown microalgae [34, 35]. The
ammonium and other nutrients, together with medium and short-
major advantages of these treatments are that additional pollution is
chain carbon compounds makes these streams ideal for microalgae
not generated when the biomass is harvested and a removal of
culture.
heavy metals and xenobiotics [31, 36] plus an efficient recycling of
From the point of view of anaerobic digestion plants
nutrients [37] is possible. On the other hand, an important
managers, algae growth using digestate has significant economic
disadvantage is the cost involved in treating very large volumes of
and environmental benefits. Biogas plants are rich sources of
wastewater in a timely manner under autotrophic conditions [38].
mineral nutrients, CO2 and heat. By algal treatment of biogas
To date, wastewater treatment using microalgae has hardly
digestate, it is possible to improve the quality of digestate liquid
been tested under heterotrophic conditions [38]. Nonetheless,
fraction, reduce energy consumption compared to classical
Chlorella spp. and strains of Scenedesmus were isolated from
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Citation: Dolores Hidalgo (2015), Heterotrophic Microalgae Cultivation to Synergize Anaerobic Digestate Treatment with Slow-Release
Fertilizers and Biostimulants Production. AOP J Environ Waste Management 1:101
http://dx.doi.org/10.14437/AOPJEWM-1-101
Page 4 of 12
wastewater treatment, solve digestate logistic problems, produce
for algal growth in swine manure digestates. On the other hand, the
algae which can be used as an energetic substrate or processed in
digestate phosphorus concentration was found to have no impact on
biorefineries, recycle CO2 emissions, effectively use excess heat
micro algal growth due to the phosphorus storage capacity of
and reduce odor of digestate. Furthermore, nutrients are recovered
microalgae [50]. Uggetti et al. [44] grew mixed micro algal culture
and cycled on-site.
dominated by Scenedesmus sp. in municipal treatment plant
However the use of anaerobic digestate as a nutrient
digestate detecting that biomass production was positively
source for microalgae may affect sometimes growth rates, lipid
correlated with the inoculum and substrate concentrations.
production, and the growth of undesired organisms when compared
Algal based biofertilizers and biostimulants production
to levels achieved with expensive defined media [41, 42]. As
The main driving force to grow microalgae is harvesting
previously mentioned, a major source of nitrogen within the
products of commercial interest, such as feed for animals (livestock
anaerobic digestate is ammonia. In general, nitrogen has a marked
and fishes), food supplements for humans, fertilizers, biofuels, and
positive effect on microalgae growth but some studies have
phytoremediation of toxic wastes. Many initiatives have been
observed micro algal growth inhibition with the use of anaerobic
investigated; being the production of biofuels the most studied
digestate that is high in ammonia [43].With the use of an optimal
option up to now.
concentration of anaerobic digestate, growth inhibition can be
avoided and the growth of microalgae can be supported [44].
The main attractiveness of heterotrophic cultivation is that
it is potentially substantially cheaper that autotrophic cultivation.
After carbon, nitrogen is quantitatively the most important
There are many products in the agricultural, chemical or food
element contributing to the dry matter of micro algal cells. Carbon
industry that could be produced using more sustainable inputs
and nitrogen metabolism are linked in microalgae because they
through heterotrophic microalgae cultivation and which can be
share the energy generated during metabolic processes inside the
produced locally with a lower impact on natural resources.
cell. Microalgae are able to assimilate a variety of nitrogen sources,
Biofertilizers and biostimulants are a good example.
mainly ammonia, nitrate and urea, among other sources [20, 45],
Economical way of algal cultivation for biofertilizers
although a preference for ammonium has clearly been demonstrated
depends on the source of nutrients and organic carbon used.
for Chlorella spp. and Dunalliela spp., [2].
Integrating fertilizers production and waste streams treatment is a
Several studies have tested algal strains for the treatment
highly selective strategy in enhancing the cost effectiveness and
of the manure digestate. The results are still preliminary but
environmental sustainability of the whole process.
promising. Scenedesmus sp. cultivation in fermented swine
On the other hand, Europe is marked by intensive livestock
wastewater yielded good value added production in association
production. This has led to manure surpluses and excessive manure
with nutrient removal [29, 39]. Wang et al. [46], Levine et al. [47],
application on agricultural fields. As a direct consequence, the
Yang et al. [48] and Franchino et al. [39] concluded that using
amount of unconsumed nutrients in the soil has gradually increased,
microalgae may be an appropriate way of digestate treatment.
resulting in phosphorus-saturated soils, eutrophicated surface
These authors have studied the biomass growth and nutrient
waters and groundwater too rich in nitrate [51]. Microalgae can be
recovery by the green algae Neochloris oleoabundans and
implemented to convert nutrient rich streams from different
Chlorella sp. Results showed a high removal efficiency of main
processes to slow-release fertilizers that have less adverse effects
nutrients. Franchino et al. [39] compare the behavior of three
on the environment than direct application of these streams or
microalgae strains: Neochloris oleoabundans, Chlorella vulgaris
conventional fertilizers.
and Scenedesmus obliquus, when cultivated on agro-zootechnical
The European Commission, through the Nitrates Directive
digestate concluding that the three strains almost completely
(91/676/EEC), aims to reduce nitrate pollution from agricultural
remove different nitrogen forms and phosphate with C. vulgaris
sources in surface and groundwater by imposing measures such as
presenting the highest elimination capacity of ammonium.
limitation of manure application, requiring a minimum manure
Bjornsson et al. [49] showed that magnesium was critically limiting
storage capacity and manure treatment in designated “nitrate
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Citation: Dolores Hidalgo (2015), Heterotrophic Microalgae Cultivation to Synergize Anaerobic Digestate Treatment with Slow-Release
Fertilizers and Biostimulants Production. AOP J Environ Waste Management 1:101
http://dx.doi.org/10.14437/AOPJEWM-1-101
Page 5 of 12
vulnerable zones” (> 50 mg NO3/L in groundwater). Outside
By reducing the volume of the liquid digestate, the nutrients
“nitrate vulnerable zones” the voluntary adoption of codes of good
become more manageable and some reclaimed water may be
practice is encouraged [52].
produced. Several authors have shown that dried algal biomass
In contrast to nitrogen whose supply is not limited,
produced from the treatment of anaerobically digested manure
phosphorus is considered a strategic resource. The main source of
could be a good substitute for commercial fertilizers [44, 57, 58].
phosphorus is mined as phosphate rock. The demand for
According these authors, dry algae do not contain free ammonia or
phosphorus has been increasing rapidly since 1960. Phosphate rock
nitrate that can leach into the environment or volatize at the time of
is only found in a limited number of countries, all of which are
application. Furthermore, concentration of heavy metals in
outside of Europe [53].
microalgae grown on manure digestate are low enough not to
In 2008, year characterized by changing economic and
reduce its value as soil or feed amendment.
geopolitical conditions, fertilizer prices increased rapidly by 800%,
Living microalgae can also be used as a nitrogen fixator to
as a result of an increase in energy prices, increased demand for
bring atmospheric nitrogen into the soil and as soil conditioner [3].
fertilizers due to increased meat-based diets, increase in biofuel
Microalgae can be also further processed (e.g. hydrolyzed) in order
production, and panic buying by large consumers [53]. Since 2010
to obtain more elaborated biofertilizers and biostimulants.
Microalgae based products can increase the plants’
phosphate prices have experienced a gradual increase, and it is
believed that they will continue to rise in the future [54].
resistance against biotic and abiotic stresses. Several studies show
Trying to face this situation, the European Commission
that the application of microalgae extracts on agricultural crops
has identified minimizing losses from agro-ecosystems and
lead to better growth and yield performance [59-62]. Increased
recovering and reuse of nutrients (NPK) from all kinds of waste
antioxidant content, higher antioxidant activity, better root
streams as a key area of research. On-going EU funded research is
development, and higher number and weight of fruits and seeds are
addressing the question of how to reduce the use of mineral
some of the effects that were observed during the experiments.
fertilizers in agriculture and optimize the application of nutrients [3,
Voort et al. [3] mention different researches carried out on this
53].
issue: Oancea et al. [63] demonstrated the Nannochloris sp.
As
previously
mentioned,
manure
digestate
is
alleviates the negative effects of drought stress on plant
characterized by a high mineral load, mainly nitrogen and
development in tomatoes; El-Naggar et al. [64] observed that
phosphorus and it is usually directly used as fertilizer in agriculture.
aqueous extracts of Chlorella kessleri increased the percentage of
A potential method of nutrient extraction from organic wastes is the
germination, seedling growth parameters, leaf area, pigments
production of proteinaceous biomass by cultivating algae [55]. This
content and the fresh and dry weights of roots and shoots of Vivia
increases the value and manageability of the nutrients. Harvested
faba (broad bean); Dasgan et al. [65] showed that Chlorella extracts
algal biomass can be used as a slow release fertilizer with reduced
allowed reducing the nutrient input and still obtain the same growth
risk of losing nutrients to the environment by leaching or by
characteristics in soilless-grown squash.
gaseous emissions of ammonia [49]. Manure digestate is an
The work on micro algal biostimulants is a rather recent
especially attractive feedstock to grow microalgae, as it is less
phenomenon in comparison to biostimulants made from seaweed
contaminated than sewage sludge digestate, for example [3].
that have been on the market since the early 1980s. The
There is increased interest in creating improved fertilizer
products from manure digestate, in order to increase its value,
commercialization of biostimulants from microalgae is starting to
take off.
secure outlets and potentially generate an additional revenue stream
Almost all the commercial microalgae biostimulants are
for the biogas plant [56]. Microalgae could be used to recover
based on the commonly produced microalgae, like Spirulina,
nutrients from the liquid fraction of digestate and as microalgae
Chlorella, Nannochloropsis and Scenedesmus. To avoid variability
incorporate these nutrients into their biomass, a fertilizer is created
in the microalgae composition, producers prefer to grow these
that is less prone to nutrient losses towards the environment [55].
organisms in fresh water with chemical addition of nutrients and
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Citation: Dolores Hidalgo (2015), Heterotrophic Microalgae Cultivation to Synergize Anaerobic Digestate Treatment with Slow-Release
Fertilizers and Biostimulants Production. AOP J Environ Waste Management 1:101
http://dx.doi.org/10.14437/AOPJEWM-1-101
Page 6 of 12
CO2 as carbon source. The challenge here is to substitute
of algae biomass and favors sustainable economics.
the source of nutrients and carbon and the culture mode in order to
In conclusion, the growing interest in microalgae, either
reduce production costs and, thus, improve the competitiveness of
non-modified or with appropriate genetic modification, suggests
the final products.
that
heterotrophic
micro
algal
processes
offer
significant
According to Voort et al. [3], the market outlook for
commercial opportunities. However, key aspects in heterotrophic
biostimulants is good, as certain pesticides are (gradually)
cultivation such as effluents (source of carbon and nutrients)
withdrawn from the market due to the application of current
availability, cultivation system design, productivity of algal culture,
legislation (e.g. the EU Pesticide Authorization Directive, EC
nutrient uptake, strain improvement, biomass harvesting and
91/414). Furthermore, concerns about the development of
extraction, refining and residual biomass utilization, etc. needs
resistance against commonly used pesticides, increasing costs of
further attention.
fertilizers and the anticipated effects of climate change in Europe
The availability of water and nutrients to promote micro
provide an impetus for the development and commercialization of
algal growth are determinant to the success of this fertilizers
micro algal biostimulants.
source,
both in terms of economic
competitiveness and
Applying organic bio products to agricultural land could
environmental impact. In fact, based on the current technology,
increase the amount of carbon stored in these soils and contribute
micro algal cultivation for fertilizers production is economically
significantly to the reduction of greenhouse gas emissions by
viable only if wastewater is used as source of water and nutrients.
eliminating the requirement of fossil fuels for production through
For this reason, coupling microalgae culture for fertilizers
reclamation of N:P:K from wastewater streams. Furthermore,
production and manure digestate treatment is nowadays seen as an
increasing organic matter in soils may cause other greenhouse gas-
appropriate and economic solution.
saving effects, such as improved workability of soils, better water
Microalgae could be implemented in the short term as a
retention, less production and use of mineral fertilizers and
solution to convert nutrient rich streams from different processes to
pesticides, and reduced release of nitrous oxide [61].
slow-release fertilizers with less adverse effects on the environment
Concluding Remarks
than the direct application of these streams on soils or conventional
Microalgae of numerous heterotrophic genera show
considerable metabolic versatility and flexibility but they are
fertilizers.
Acknowledgments
currently underexploited in the biotechnological manufacturing.
The authors gratefully acknowledge support of this work by
Heterotrophic cultivation is an interesting niche of microalgae
the LIFE+ Program under the responsibility of the Directorate
research field mainly related with economic aspects (cost
General for the Environment of the European Commission (project
effectiveness of the processes), although a limitation exists due to
LIFE 12 ENV/ES/000107-REVAWASTE).
the short number of microalgae able to grow in the absence of light.
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Citation: Dolores Hidalgo (2015), Heterotrophic Microalgae Cultivation to Synergize Anaerobic Digestate Treatment with Slow-Release
Fertilizers and Biostimulants Production. AOP J Environ Waste Management 1:101
http://dx.doi.org/10.14437/AOPJEWM-1-101
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Page 11 of 12
Table 1: Growth characteristics of microalgae in heterotrophic batch cultures (adapted from Bumbak et al. [22])
Yx/s (gCDW g-1)
T
pH
Carbon soures
Sinhib (g l-1)
Products
0.035
0.52
(ºC)35
36
6.9
Acetate
>0.4
Biomass
P/H
0.090
0.47
28
6.6
Glucose (acetate, glycerol)
24
Lutein, lipids, biodiesel
P/H
0.201
0.50
35
6.9
Glucose (acetate, glutamate, lactate)
>10
violaxanthin
Ascorbic acid, lutein
Chlorella regularis
Chlorella vulgaris
Chlorella
P/H
P/H
P/H
0.240
0.180
0.031
0.60
0.55-0.69
0.44
36
36
30
6.5
6.0-7.5
5.5
Glucose (acetate, ethanol)
Glucose (acetate, glutamate, lactate)
Glucose (fructose, galactose, mannose,
>10
n.a.
>20
Biomass,intracellular phytochemicals
Biomass
Astaxanthin
zofingiensis
Crypthecodinium
H
0.089
0.56
25
7.2
lactose, sucrose)
Glucose (acetate)
>20
DHA
cohnii
Dunaliella sp.
P/H
<0.010
n.a.
26
7.5-8.3
Acetate, lactate, glucose, glutamate, glycerol
n.a.
Biomass beta-carotene
Euglena gracilis
P/H
0.045
0.43
25
2.8-3.5
Glucose, (acetate, alanine, aspartate, asparagine,
n.a.
Alpha-tocopherol
Galdieria
P/H
0.045-0.048
0.48-0.50
42
2.0
ethanol, glutamate)
Glucose
>200
Phycocyanin
>350
>1.6
Astaxanthin,
Species
Type
Chlamydomonas
P/H
reinhardtii
Chlorella
protothecoides
Chlorella
max (h
-1
)
pyrenoidosa
sulphuraria
Haematococcus
P/H
0.009
n.a.
25
8.0
Sugar beet molasses (fructose, sucrose)
Acetate (glucose, asparagine)
pulvialis
Nannochloropsis
P/H
<0.007
n.a.
26
7.5-8.3
Glucose (ethanol)
n.a.
cantaxanthin, lutein
Biomass, EPA
Nitzschia alba
H
0.106
n.a.
30
n.a.
Lactate, succinate, glucose, glutamate
n.a.
Biomass, EPA
Nitzschia laevis
H
0.017
0.44
20
8.2
Acetate, glucose
n.a.
EPA
Prototheca zopfii
H
0.330
0.81
21
7.2
Glucose (acetate)
n.a.
L-Ascorbic acid
Scenedesmus actus
P/H
0.040
n.a.
30
6.0
Glucose
>1
Biomass
Schizochytrium sp.
H
0.071
0.42
27
7.0
Glucose
>200
PUFA, DHA, GLA
Tetraselmis sueica
P/H
0.028
0.41
25
7.5
Acetate (glucose, glutamine, lactate)
n.a.
Lipids, PUFA n-3 HUFA
oculata
Citation: Dolores Hidalgo (2015), Heterotrophic Microalgae Cultivation to Synergize Anaerobic Digestate Treatment with Slow-Release Fertilizers and Biostimulants Production. AOP J Environ
Waste Management 1:101
http://dx.doi.org/10.14437/AOPJEWM-1-101
Page 12 of 12
μmax maximum specific growth rate, Yx/s biomass yield determined in batch culture at given temperature (T), S inhib substrate concentration resulting in a decrease of the specific growth rate and/or
biomass yield with the particular substrate, H heterotroph, P (facultatively) photoautotroph, n.a. not available, DHA docosahexaenoic acid, EPA eicosapentaenoic acid, GLA gamma-linolenic acid,
HUFA highly unsaturated fatty, PUFA polyunsaturated fatty acids.
Table 2: Examples of wastewater treatment with algae in heterotrophic mode (adapted from Mohan et al. [18]).
Species
Wastewater used
Lipid productivity
Reference
Chlorococcum sp. RAP13
Dairy effluent
42%
[70]
Scenedesmus sp.
Fructose, glucose and acetate
52.6%
[71]
Botryococcus braunii
Secondary treated sewage
17%
[72]
Mixed culture
Carpet mill effluent
Mixed culture
Domestic wastewater
28.2%
[74]
Mixed culture
Acid-rich effluents from hydrogen producing
26.4%
[75]
[73]
reactor
Mixed culture Volatile fatty acids
Volatile fatty acids
Scenedesmus sp. LX1
Secondary effluent from a domestic
[76]
31–33%
[41]
wastewater Treatment
Chlorella vulgaris
Agro-industrial co-products, ethanol thin stillage
43%/9.8 g/l
[77]
Chlorella vulgaris
and soy whey
Synthetic wastewater
22.4%
[16]
Mixed
Concentrated municipal wastewater
77 mg/l/d
[78]
Auxenochlorella protothecoides UMN 280
Municipal wastewater
28%
[79]
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